supply – Experimental Engineering

Posted on June 15, 2018May 3, 2018 by The Engineer — Leave a comment

Turbine Fuel Pump Extreme Teardown

Here’s a destructive teardown of an automotive in-tank turbine fuel pump, used on modern Petrol cars. These units sit in the tank fully immersed in the fuel, which also circulates through the motor inside for cooling. These pumps aren’t serviceable – they’re crimped shut on both ends. Luckily the steel shell is thin, so attacking the crimp joint with a pair of mole grips & a screwdriver allowed me inside.

The input endbell of the pump has the fuel inlet ports, the channels are visible machined into the casting. There’s a pair of channels for two pump outputs – the main fuel rail to the engine, and an auxiliary fuel output to power a venturi pump. The fuel pump unit sits inside a swirl pot, which holds about a pint of fuel. These are used to ensure the pump doesn’t run dry & starve the engine when the tank level is low & the car is being driven hard. The venturi pump draws fuel from the main tank into the swirl pot. A steel ball is pressed in to the end bell to provide a thrust bearing for the motor armature.

The core of the pump is this impeller, which is similar to a side-channel blower. From what I’ve been able to find these units supply pressures up to about 70PSI for the injector rail. The outside ring is the main fuel pump, while the smaller inner one provides the pressure to run the venturi pump.

The other side of the machined pump housing has the main output channel, with the fuel outlet port at the bottom. The motor shaft is supported in what looks like a carbon bearing.

Removing the pump intermediate section with the bearing reveals quite a bit of fungus – it’s probably been happy sat in here digesting what remains of the fuel.

Some peeling with mole grips allows the motor to come apart entirely. The drive end of the armature is visible here.

The outer shell of the motor holds yet more fungus, along with some rust & the pair of ceramic permanent magnets.

The other end of the pump has the brush assembly, and the fuel outlet check valve to the right. The bearing at this end is just the plastic end cap, since there are much lower forces at this end of the motor. The fuel itself provides the lubrication required.

With the armature pulled out of the housing, it’s clear that there’s been quite a bit of water in here as well, with the laminations rusting away. This armature is fully potted in plastic, with none of the copper windings visible.

The commutator in these motors is definitely a strange one – it’s axial rather than radial in construction, and the segments are made of carbon like the brushes. No doubt this is to stop the sparking that usually occurs with brushed motors – preventing ignition of fuel vapour in the pump when air manages to get in as well, such as in an empty tank.

Posted on May 4, 2017May 8, 2017 by The Engineer — 1 Comment

32A Bench PSU Build

Since I’ve discovered some nice high power PSUs in the form of Playstation 3 PSUs, it’s time to get a new Bench PSU Build underway!

I’ve gone for the APS-227 version as it’s got the 32A rail. This makes things slightly beefier overall, as the loading will never be anywhere close to 100% for long, more headroom on the specs is the result.

The case I’ve chosen for this is an ABS desktop instrument case from eBay, the TE554 200x175x70mm. The ABS is easy to cut the holes for all the through-panel gear, along with being sturdy enough. Aluminium front & back panels would be a nice addition for a better look.

The PSU board is removed from it’s factory casing & installed on the bottom shell half, unfortunately the moulded-in posts didn’t match the screw hole locations so I had to mount some brass standoffs separately. The AC input is also fitted here, I’ve used a common-mode filter to test things (this won’t be staying, as it fouls one of the case screw holes). The 40A rated DC output cable is soldered directly to the PCB traces, as there’s no room under the board to fit the factory DC power connector. (This is the biggest case I could find on eBay, and things are still a little tight). Some minor modifications were required to get the PCB to fit correctly.

I decided to add some limited voltage adjustment capability to the front panel, I had a 100Ω Vishay Spectrol Precision 10-turn potentiometer in my parts bin, from a project long since gone that just about fits between the panel & the output rectifier heatsink. The trimpot I added when I first posted about these PSUs is now used to set the upper voltage limit of 15 volts. (The output electrolytics are 16v rated, and are in an awkward place to get at to change for higher voltage parts). The binding posts are rated to 30A, and were also left over from a previous project.

This front panel potentiometer is electrically in series with the trimpot glued to the top of the auxiliary transformer, see above for a simple schematic of the added components. In this PSU, reducing the total resistance in the regulator circuit increases the voltage, so make sure the potentiometer is wired correctly for this!
After some experimentation, a 500Ω 10-turn potentiometer would be a better match, with a 750Ω resistor in parallel to give a total resistance range on the front panel pot of 300Ω. This will give a lower minimum voltage limit of about 12.00v to make lead-acid battery charging easier.
I’ve had to make a minor modification to the output rectifier heatsink to get this pot to fit in the available space, but nothing big enough to stop the heatsink working correctly.

Here I’ve got the binding posts mounted, however the studs are a little too long. Once the wiring is installed these will be trimmed back to clear both the case screw path & the heatsink. (The heatsink isn’t a part of the power path anyway, so it’s isolated).

To keep the output rectifier MOSFETs cool, there’s a fan mounted in the upper shell just above their location, this case has vents in the bottom already moulded in for the air to exit. The fan is operated with the DC output contactor, only running when the main DC is switched on. This keeps the noise to a minimum when the supply doesn’t require cooling. The panel meter control board is also mounted up here, in the only empty space available. The panel meter module itself is a VAC-1030A from MingHe.

The measurement shunt & main power contactor for the DC output is on another board, here mounted on the left side of the case. The measurement shunt is a low-cost one in this module, I doubt it’s made of the usual materials of Manganin or Constantan, this is confirmed by my meansurements as when the shunt heats up from high-power use, the readings drift by about 100mA. The original terminal blocks this module arrived with have been removed & the DC cables soldered directly to the PCB, to keep the number of high-current junctions to a minimum. This should ensure the lowest possible losses from resistive heating.

The panel meter module iself is powered from the 5v standby rail of the Sony PSU, instead of the 12v rail. This allows me to keep the meter on while the main 12v output is switched off.

here’s the supply with everything fitted to the lower shell – it’s a tight fit! A standard IEC connector has been fitted into the back panel for the mains input, giving much more clearance for the AC side of things.

With the top shell in place, a look through the panel cutout for the meter LCD shows the rather tight fit of all the meter components. There’s about 25mm of clearance above the top of the PSU board, giving plenty of room for the 40mm cooling fan to circulate air around.

Here’s the finished supply under a full load test – it’s charging a 200Ah deep cycle battery. The meter offers many protection modes, so I’ve set the current limit at 30A – preventing Sony’s built in over current protection on the PSU tripping with this function is a bonus, as the supply takes a good 90 seconds to recover afterwards. I’ll go into the many modes & features of this meter in another post.

Posted on April 11, 2017May 1, 2017 by The Engineer — 10 Comments

Sony PS3 APS-231 Power Supply Voltage Mod

I was recently given a Sony PS3 with a dead disc drive, and since I’m not a console gamer I figured I’d see if there were any handy parts inside. Turns out these units contain a rather nice SMPS, the Sony APS-231 with a high power 12v rail, rated at 23.5A. A bit of searching around discovered a thread on the BadCaps Forums about voltage modding these supplies for a 13.8v output, suitable for my Ham radio gear.
These supplies are controlled by a Sony CXA8038A, for which there is very little information. Active PFC is included, along with synchronous rectification which increases the efficiency of the supply, and in turn, reduces the waste heat output from the rectifiers.

Like many of the SMPS units I’ve seen, the output voltage is controlled by referencing it to an adjustable shunt reference, and adjusting the set point of this reference will in turn adjust the output voltage of the supply, this is done in circuit by a single resistor.

Here’s the regulator section of the PSU, with the resistors labelled. The one we’re after changing is the 800Ω one between pins 2 & 3 of the TS2431 shunt reference. It’s a very small 0402 size resistor, located right next to the filter electrolytic for the 5v standby supply circuit. A fine tip on the soldering iron is required to get this resistor removed.

Once this resistor is removed from the circuit, a 1KΩ 18-turn potentiometer is fitted in it’s place, from the Anode (Pin 3) to the Ref. (Pin 2) pins of the TS2431 shunt reference. I initally set the potentiometer to be the same 800Ω as the factory set resistor, to make sure the supply would start up at a sensible voltage before I did the adjustment.

The pot is secured to the top of the standby supply transformer with a drop of CA glue to stop everything moving around. The supply can now be adjusted to a higher setpoint voltage – 13.8v is about the maxumum, as the OVP cuts the supply out at between 13.9v-14v.

After doing some testing at roughly 50% of the supply’s rated load, everything seems to be stable, and nothing is heating up more than I’d expect.

Posted on March 12, 2017April 24, 2017 by The Engineer — 11 Comments

Jaguar S-Type Aux Heater / Webasto Thermo Top V Part 2 – W-Bus Diagnostics

As I mentioned in the previous post, these heaters have a standard interface that’s used for control & diagnostics, the W-Bus. This is transmitted over the K-Line of the vehicle bus, and all heaters, regardless of firmware modifications done by the various car manufacturers respond to this interface. Official Webasto diagnostic adaptors are available, but these are just a very expensive serial adaptor. A much cheaper option is a ~£5 Universal ODB adaptor.

Above shows the signals on the ODB connector – the ones we’re interested in here are Pin 16, the +12v supply, and Pin 7, K-Line. Connect Pin 16 to the positive supply to the heater, and Pin 7 to Pin 2 on the Webasto heater. (Valid for all TT-V heaters).

Once these two connections are made to the heater, fire up the Thermo Test software. The screen above will be displayed. Pick W-Bus at top left.

First thing, connect the ODB adaptor to USB, and change to the correct COM port in Thermo Test. There may be several in the list, but a newly connected USB device should show up with the highest COM number.

Once Thermo Test is running, start communications by going to the Diagnosis Menu > Start Diagnostic (F2 keyboard shortcut).

After a few seconds, communication will be established. This will show faults, if any are present, and allow testing of the heater & it’s component parts. A summary report can be generated with Diagnosis > View Summary:

Diagnosis report                                               Webasto Thermosystems
------------------------------------------------------------------------------------------


Configuration:
--------------
  W-Bus version...............................................................3.3           
  Device name.............................................................X204 SH           
  W-Bus code.......................................................715CC0E73F8000           
  Fuel type................................................................Diesel           
  Circulating pump in control idle period.......................................0           
  Heating duration limitation.................................................255 [min]     
  Factor for shortening of ventilation duration...............................1/1           
  Device identification number..........................................09007236E           
  Dataset identification number.......................................09006806H05           
  Software identification number........................................000000000           
  HW version................................................................51/03           
  SW version..................................................Tuesday/07/04 12.12           
  SW version (EEPROM).........................................Tuesday/07/04 12.12           
  Date of manufacture control unit.......................................27.10.03           
  Date of manufacture heater.............................................04.02.04           
  Customer identification number.....................................4R8318K463AE           
  Serial number........................................................0000123626           
  Test signature.............................................................4B42           
  Minimum voltage threshold....................................................10 [V]       
  Maximum voltage threshold....................................................16 [V]       
  Delay for supply voltage min. detection......................................20 [s]       
  Delay for supply voltage max. detection.......................................6 [s]       

Operating data:
---------------
  Working hours.............................................................44:03 [h:m]     
  Operating hours.........................................................5388:08 [h:m]     
  Start count...............................................................19129           
  Burning duration PH 1..33%.................................................0:00 [h:m]     
  Burning duration PH 34..66%................................................0:00 [h:m]     
  Burning duration PH 67..100%...............................................0:00 [h:m]     
  Burning duration PH >100%..................................................0:00 [h:m]     
  Burning duration SH 1..33%.................................................0:00 [h:m]     
  Burning duration SH 34..66%................................................0:00 [h:m]     
  Burning duration SH 67..100%...............................................0:00 [h:m]     
  Burning duration SH >100%..................................................0:00 [h:m]     
  Working duration PH........................................................0:51 [h:m]     
  Working duration SH......................................................121:10 [h:m]     
  Start counter PH..............................................................6           
  Start counter SH............................................................854           
  Ventilation duration.......................................................0:00 [h:m]     

Error:
------

------------------------------------------------------------------------------------------
12.03.17  17:17:30                                       Webasto Thermo Test  2.16.1

Diagnosis report Webasto Thermosystems

------------------------------------------------------------------------------------------

Configuration:

--------------

W-Bus version...............................................................3.3

Device name.............................................................X204 SH

W-Bus code.......................................................715CC0E73F8000

Fuel type................................................................Diesel

Circulating pump in control idle period.......................................0

Heating duration limitation.................................................255 [min]

Factor for shortening of ventilation duration...............................1/1

Device identification number..........................................09007236E

Dataset identification number.......................................09006806H05

Software identification number........................................000000000

HW version................................................................51/03

SW version..................................................Tuesday/07/04 12.12

SW version (EEPROM).........................................Tuesday/07/04 12.12

Date of manufacture control unit.......................................27.10.03

Date of manufacture heater.............................................04.02.04

Customer identification number.....................................4R8318K463AE

Serial number........................................................0000123626

Test signature.............................................................4B42

Minimum voltage threshold....................................................10 [V]

Maximum voltage threshold....................................................16 [V]

Delay for supply voltage min. detection......................................20 [s]

Delay for supply voltage max. detection.......................................6 [s]

Operating data:

---------------

Working hours.............................................................44:03 [h:m]

Operating hours.........................................................5388:08 [h:m]

Start count...............................................................19129

Burning duration PH 1..33%.................................................0:00 [h:m]

Burning duration PH 34..66%................................................0:00 [h:m]

Burning duration PH 67..100%...............................................0:00 [h:m]

Burning duration PH >100%..................................................0:00 [h:m]

Burning duration SH 1..33%.................................................0:00 [h:m]

Burning duration SH 34..66%................................................0:00 [h:m]

Burning duration SH 67..100%...............................................0:00 [h:m]

Burning duration SH >100%..................................................0:00 [h:m]

Working duration PH........................................................0:51 [h:m]

Working duration SH......................................................121:10 [h:m]

Start counter PH..............................................................6

Start counter SH............................................................854

Ventilation duration.......................................................0:00 [h:m]

Error:

------

------------------------------------------------------------------------------------------

12.03.17 17:17:30 Webasto Thermo Test 2.16.1

This shows all the important stuff, including running hours. (5388Hrs on this heater!). Most importantly, there are no faults listed.

The heater can be fully tested by issuing a start command from the Command Menu > Parking Heating option. Obviously cooling water will be required for this, along with an external water pump. (The water pump control output on these heaters seems to be totally disabled in firmware, as they rely on the engine’s coolant pump). I used a bucket of water along with a small centrifugal pump to provide the cooling. During this test I noted that the firmware is much more aggressive in these units. The marine versions shut down at ~72°C water temperature, whereas these don’t so the same until ~90°C.

Now I’ve managed to communicate with the heater, I’ll get onto building a standalone controller so I can dispense with the Windows VM for control.

Posted on March 4, 2017April 24, 2017 by The Engineer — Leave a comment

IC Decap – TDA3606 Multi Regulator With Battery Sense

This is a chip aimed at the automotive market – this is a low power voltage regulator for supplying power to microcontrollers, for instance in a CD player.

The TDA3606 is a voltage regulator intended to supply a microprocessor (e.g. in car radio applications). Because of low voltage operation of the application, a low-voltage drop regulator is used in the TDA3606. This regulator will switch on when the supply voltage exceeds 7.5 V for the first time and will switch off again when the output voltage of the regulator drops below 2.4 V. When the regulator is switched on, the RES1 and RES2 outputs (RES2 can only be HIGH when RES1 is HIGH) will go HIGH after a fixed delay time (fixed by an external delay capacitor) to generate a reset to the microprocessor. RES1 will go HIGH by an internal pull-up resistor of 4.7 kΩ, and is used to initialize the microprocessor. RES2 is used to indicate that the regulator output voltage is within its voltage range. This start-up feature is built-in to secure a smooth start-up of the microprocessor at first connection, without uncontrolled switching of the regulator during the start-up sequence. All output pins are fully protected. The regulator is protected against load dump and short-circuit (foldback
current protection). Interfacing with the microprocessor can be accomplished by means of a battery Schmitt-trigger and output buffer (simple full/semi on/off logic applications). The battery output will go HIGH when the battery input voltage exceeds the HIGH threshold level.

Posted on February 9, 2017February 9, 2017 by The Engineer — 3 Comments

Anker PowerPort Speed 5 USB Rapid Charger Teardown

Here’s a piece of tech that is growing all the more important in recent times, with devices with huge battery capacities, a quick charger. This unit supports Qualcomm’s Quick Charge 3 standard, where the device being charged can negotiate with the charger for a higher-power link, by increasing the bus voltage past the usual 5v.

The casing feels rather nice on this unit, sturdy & well designed. All the legends on the case are laser marked, apart from the front side logo which is part of the injection moulding.

The power capacity of this charger is pretty impressive, with outputs for QC3 from 3.6-6.5v at 3A, up to 12v 1.5A. Standard USB charging is limited at 4.8A for the other 3 ports.

The two of the 5 USB ports are colour coded blue on the QC3 ports. The other 3 are standard 5v ports, the only thing that doesn’t make sense in the ratings is the overall current rating of the 5v supply (4.8A), and the rated current of each of the ports (2.4A) – this is 7.2A total rather than 4.8A.

The casing is glued together at the seam, but it gave in to some percussive attack with a screwdriver handle. The inside of this supply is mostly hidden by the large heatspreader on the top.

This is a nicely designed board, the creepage distances are at least 8mm between the primary & secondary sides, the bottom also has a conformal coating, with extra silicone around the primary-side switching transistor pins, presumably to decrease the chances of the board flashing over between the close pins.
On the lower 3 USB ports can be seen the 3 SOT-23 USB charge control ICs. These are probably similar to the Texas Instruments TPS2514 controllers, which I’ve experimented with before, however I can’t read the numbers due to the conformal coating. The other semiconductors on this side of the board are part of the voltage feedback circuits for the SMPS. The 5v supply optocoupler is in the centre bottom of the board.

Desoldering the pair of primary side transistors allowed me to easily remove the heatspreader from the supply. There’s thermal pads & grease over everything to get rid of the heat. Here can be seen there are two transformers, forming completely separate supplies for the standard USB side of things & the QC3 side. Measuring the voltages on the main filter capacitors showed me the difference – the QC3 supply is held at 14.2v, and is managed through other circuits further on in the power chain. There’s plenty of mains filtering on the input, as well as common-mode chokes on the DC outputs before they reach the USB ports.

Here’s where the QC3 magic happens, a small DC-DC buck converter for each of the two ports. The data lines are also connected to these modules, so all the control logic is located on these too. The TO-220 device to the left is the main rectifier.

Posted on October 27, 2016 by The Engineer — Leave a comment

LG Flatron 22EA53VQ-P Power Issue

I was recently given a pretty nice LED backlit 1080p LG monitor, with the instruction that it wouldn’t power on correctly. The monitor would power on as far as the standby light, but when fully powered on, would flash the backlight momentarily then shut down. A power supply issue was immediately suspected.

I popped the covers off the monitor itself first, thinking that it was an electrolytic gone bad in the backlight DC-DC converter. Not to mention the fact that cracking into a wall-wart type of PSU is only occasionally possible without the use of anger & large hammers. (Cracking the glue with the handle of a screwdriver doesn’t work so well when the factory went a bit nuts with the glue/ultrasonic welder). As can be seen in the photo, there’s not much inside these monitors, the logic is a single-chip solution, the rest of the PCB is dedicated to supplying the power rails for the various circuits. On the left is the power input & the DC-DC converter for the backlight, along with the DC-DC converter supplying the logic circuits. None of the capacitors here are damaged, everything looks good.
I then measured the output of the PSU, which under no load was the correct 19v DC. However applying any load caused the output voltage to drop like a proverbial brick. Applying a full load of 1.3A saw the output voltage drop so severely that the PSU tripped on it’s UVLO.

At 200mA of load the factory PSU is already dropping to 18v, with a 5.3kHz switching frequency appearing.

At higher load the frequency increases to 11.5kHz & the output voltage has dropped to 11.86v!

750mA was as high as I could make the supply go without it tripping itself out – the UVLO circuit trips at 9v. 12.6kHz is now riding on the severely low DC at this point.

The power supply is supposed to be rated at 1.3A at 19v, however with this fault it’s getting nowhere near that. The LG brand is on this PSU but it’s contracted out to Shenzen Honor Electric Co. Ltd.

Here’s the problem with this PSU. The output electrolytic has ballooned. I don’t have an ESR tester, but this cap has gone way past it’s sell-by date. It’s position right next to the heatsink with the output rectifier diodes has probably cooked it. The PSU isn’t that badly built for a Chinese one – there’s plenty of creepage distance on the PCB & even a couple of isolation slots.

Posted on October 11, 2016 by The Engineer — Leave a comment

eBay Chinese Chassis Power Supply S-400-12 400W 12v 33A

Here’s a cheap PSU from the treasure trove of junk that is eBay, rated at a rather beefy 400W of output at 12v – 33A! These industrial-type PSUs from name brands like TDK-Lambda or Puls are usually rather expensive, so I was interested to find out how much of a punishment these cheap Chinese versions will take before grenading. In my case this PSU is to be pushed into float charging a large lead acid battery bank, which when in a discharged state will try to pull as many amps from the charger as can be provided.

These PSUs are universal input, voltage adjustable by a switch on the other side of the PSU, below. The output voltage is also trimmable from the factory, an important thing for battery charging, as the output voltage needs to be sustained at 13.8v rather than the flat 12v from the factory.

Mains connections & the low voltage outputs are on beefy screw terminals. The output voltage adjustment potentiometer & output indicator LED are on the left side.

The cooling fan for the unit, which pulls air through the casing instead of blowing into the casing is a cheap sleeve bearing 60mm fan. No surprises here. I’ll probably replace this with a high-quality ball-bearing fan, to save the PSU from inevitable fan failure & overheating.

The PCB tracks are generously laid out on the high current output side, but there are some primary/secondary clearance issues in a couple of places. Lindsay Wilson over at Imajeenyus.com did a pretty thorough work-up on the fineries of these PSUs, so I’ll leave most of the in-depth stuff via a linky. There’s also a modification of this PSU for a wider voltage range, which I haven’t done in this case as the existing adjustment is plenty wide enough for battery charging duty.

The PCB is laid out in the usual fashion for these PSUs, with the power path taking a U-route across the board. Mains input is lower left, with some filtering. Main diode bridge in the centre, with the voltage selection switch & then the main filter caps. Power is then switched into the transformer by the pair of large transistors on the right before being rectified & smoothed on the top left.

The pair of main switching devices are mounted to the casing with thermal compound & an insulating pad. To bridge the gap there’s a chunk of aluminium which also provides some extra heatsinking.

The PSU is controlled by a jelly-bean TL494 PWM controller IC. No active PFC in this cheap supply so the power factor is going to be very poor indeed.

Input protection & filtering is rather simple with the usual fuse, MOV filter capacitor & common mode choke.

Beefy 30A dual diodes on the DC output side, mounted in the same fashion as the main switching transistors.

Current measurement is done by these large wire links in the current path, selectable for different models with different output ratings.

The output capacitors were just floating around in the breeze, with one of them already having broken the solder joints in shipping! After reflowing the pads on all the capacitors some hot glue as flowed around them to stop any further movement.

This supply has now been in service for a couple of weeks at a constant 50% load, with the occasional hammering to recharge the battery bank after a power failure. at 13A the supply barely even gets warm, while at a load high enough to make 40A rated cable get uncomfortably warm (I didn’t manage to get a current reading, as my instruments don’t currently go high enough), the PSU was hot in the power semiconductor areas, but seemed to cope at full load perfectly well.

Posted on September 1, 2016August 16, 2016 by The Engineer — Leave a comment

eBay Flyback High Voltage PSU

I have found myself needing some more in the way of High Voltage supplies of late, with the acquisition of the new He-Ne laser tubes, so I went trawling eBay for something that would be suitable to run these tubes. (I currently only have a single He-Ne laser PSU brick, and they’re notoriously hard to find & rather expensive).
This supply is rated at 1kV-10kV output, at 35W power level. Unfortunately this supply isn’t capable of sustaining the discharge in a large He-Ne tube, the impedance of the supply is far too high. Still, it’s useful for other experiments.
The flyback-type transformer clearly isn’t a surplus device from CRT manufacture, as there are very few pins on the bottom, and none of them connect to the primary side. The primary is separately wound on the open leg of the ferrite core.

The drive electronics are pretty simple, there’s a controller IC (with the number scrubbed off – guessing it’s either a 556 dual timer or a SMPS controller), a pair of FDP8N50NZ MOSFETs driving the centre-tapped primary winding.
The drive MOSFETs aren’t anything special in this case: they’re rated at 500v 8A, 850mΩ on resistance. This high resistance does make them get rather hot even with no load on the output, so for high power use forced-air cooling from a fan would definitely be required.

Here’s the supply on test, I’ve got the scope probes connected to the gate resistors of the drive MOSFETs.

On the scope the primary switching waveforms can be seen. The FETs operate in push-pull mode, there’s a bit of a ring on the waveform, but they’re pretty nice square waves otherwise.

At maximum power on 12v input, about 25mm of gap is possible with an arc.

Posted on February 25, 2016 by The Engineer — Leave a comment

Pilot LPG Monitoring System

In my mind, the most dangerous thing onboard any boat is the LPG system, as the gas is heavier than air, any leaks tend to collect in the bilges, just waiting for an ignition source. To mitigate this possibility, we’re fitting a gas monitoring system that will sound an alarm & cut off the supply in case of a leak.

Here’s the monitor itself, the two sensor model. It’s nice & compact, and the alarm is loud enough to wake the dead.

Not much inside in the way of circuitry, the brains of the operation is a Microchip PIC16F716 8-bit microcontroller with an onboard A/D converter (needed to interface with the sensors), running at 4MHz. The solenoid valve is driven with a ULN2803 Darlington transistor array.
The alarm Piezo sounder can be seen to the right of the ICs, above that is a simple LM7805 linear regulator providing power to the electronics.

The pair of remote sensors come with 3.5m of cable, a good thing since the mounting points for these are going to be rather far from the main unit in our installation.

The sensor itself is a SP-15A Tin Oxide semiconductor type, most sensitive to butane & propane. Unlike the Chinese El-Cheapo versions on eBay, these are high quality sensors. After whiffing some gas from a lighter at one of the sensors, the alarm triggered instantly & tripped the solenoid off.

The solenoid valve goes into the gas supply line after the bottle regulator, in this case I’ve already fitted the adaptors to take the 10mm gas line to the 1/2″ BSP threads on the valve itself. This brass lump is a bit heavy, so support will be needed to prevent vibration compromising the gas line.

Posted on December 15, 2015 by The Engineer — Leave a comment

ViewSonic VA2232W-LED Monitor 12v Conversion

On the quest to get things on board replaced that are heavy users of power, the monitor in the main cabin was next. The original CCFL-backlit monitor was very heavy on 12v power, at 5A. This meant falling asleep watching TV would result in severely flattened batteries.

Replacement with a suitable LED-backlit monitor was definitely required. The cheapest on eBay was a ViewSonic VA2232W-LED, so I took to work converting it from 240v to 12v operation.

There are no screws holding these monitors together, so a spudger & frequent swearing got the back off. The shield holding the circuitry is also not screwed down, only attached to the back of the LCD panel with aluminium shielding tape.

Once the tape has been cut, the main power board is accessible. The large IC on the left is the main backlight LED driver.

In this case the monitor requires a pair of rails from the supply, 18.5v for the backlight circuitry & 5v for the logic.

A pair of DC-DC converters has been fitted in the small space between the power & control boards.

To save me some work & keep maximum compatibility, I’ve not modified the existing supply, just attached the new DC-DC converter outputs onto the corresponding outputs of the factory PSU. The 12v input leads are routed out of the same gap as the mains IEC connector, with some hot glue over the mains input solder points to provide some more insulation.

The wiring is tidied up with hot glue so the back cover will go back on.

Total current draw at 12v is 1.4A.

Posted on November 26, 2015July 13, 2016 by The Engineer — Leave a comment

nb Tanya Louise – Compressor Install

Compressed air is a rather useful power source, especially when all maintenance is done by the on board crew instead of by boatyards.

Screwfix had a good deal on a 50L 3.5CFM air compressor, to save space this has been permanently mounted in a free space & air will be piped to where it is needed from a central point.

Because of the total height of the machine, the compressor itself has been unbolted from the tank, a copper line connecting the two back together at a larger distance.

In one of the very few free spaces available, under a bunk. A pair of timbers has been screwed to the floor to support the tank.

The tank is strapped to the wooden supports with a pair of ratchet straps, the compressor itself can be seen just behind the tank. The copper line on the top of the tank is going back to be connected to the compressor outlet.

Compressor control remains on top of the tank, the pressure switch & relief valve centre. After an isolation valve, the feed splits, the regulator installed will be feeding the air horn with 20PSI, replacing the existing automotive-style 12v air pump. The currently open fitting will be routed to a quick connect on the bulkhead. This will be accessible from the front deck, an air hose can be fitted to get a supply anywhere on board.

More to come when the rest of the system gets installed!

73s for now.

Posted on October 20, 2015October 18, 2015 by The Engineer — Leave a comment

DIY SMPS Fan Controller

Now the controllers have arrived, I can rejig the supplies to have proper thermal control on their cooling.

Here’s the top off the PSU. The board has been added to the back panel, getting it’s 12v supply from the cable that originally fed the fan directly. Luckily there was just enough length on the temperature probe to fit it to the output rectifier heatsink without modification.

To connect to the standard 4-pin headers on the controller, I’ve spliced on a PC fan extension cable, as these fans spent their previous lives in servers, with odd custom connectors.

Here’s the controller itself, the temperature probe is inserted between the main transformer & the rectifier heatsink.
I’ve set the controller to start accelerating the fan at 50°C, with full speed at 70°C.

Under a full load test for 1 hour, the fan didn’t even speed up past about 40% of full power. The very high airflow from these fans is doing an excellent job of keeping the supply cool. Previously the entire case was very hot to the touch, now everything is cool & just a hint of warm air exits the vents. As the fan never runs at full speed, the noise isn’t too deafening, and immediately spools back down to minimum power when the load is removed.

Posted on October 15, 2015October 16, 2015 by The Engineer — Leave a comment

DIY SMPS Fan Speed Control – The Controllers

Finally, after a couple of weeks wait time, the fan controllers for the power supplies have arrived. They’re small boards, which is good for the small space left inside the case of the supply.

Here they are. I’m not certain what the pair of potentiometers are for – there’s no mention of them in the documentation. Possibly for calibration.
Beepers are supplied so an alarm can be heard if the fan fails – very useful for this application.

Here’s a closeup of the PCB. Options are set with the DIP switch bank on the left, details for that below. The main IC is a STM8S103F3 flash microcontroller.

The only issue at the moment is that the temperature probe leads are much too short. I’ll have to make a small modification to get enough length here.

Here’s all the details on the boards, more for future reference when they undoubtedly vanish from eBay 😉

Specifications

Working voltage:DC12V

Circuit load capacity: maximum current per output 5A, the bus currents up 9A

Output Range: The first channel 20% -100%, or 40% -100% (TFL = ON)
The second channel and the third channel 10% -100%

(Note: Above range only for PWM range, the actual control effect will vary depending on the fan.)

Temperature probe parameters: 50K B = 3950

Thermostat temperature zone error: error depending on the temperature probe, generally 3-5%

Stall alarm minimum speed: 700-800 rpm

Function setting switch Description:

TFL (No. 1): The lowest temperature channel PWM setting, when ON state FAN1 PWM minimum is 40%, when OFF the minimum PWM of FAN1 is 20%.

TP1 TP2 (No. 2,3): Temperature channel control temperature zones are interpreted as follows (need to used with the temperature probe):

TP1	TP2	Accelerating temperature	Full speed temperature
OFF	OFF	35℃	45℃
ON	OFF	40℃	55℃
OFF	ON	50℃	70℃
ON	ON	60℃	90℃

When the temperature lower than the accelerated temperature, then output at the minimum rotation speed; when it exceed over the full temperature, then always output at full speed.

BF1 BF2 (No. 4,5): corresponds FAN1 FAN2 stall alarm function switch, when the corresponding open channel fan break down, the controller will alarm with soundand light (works with buzzle), alarm will automatically eliminated when the fan is rotated recovery . If BF1 and BF2 both are open (ON), the FAN1, FAN2 have any one or both stops, the controller will alarm!

Posted on October 6, 2015 by The Engineer — Leave a comment

µRadMonitor RRDTool Graphing

I’ve been meaning to sort some local graphs out for a while for the radiation monitor, and I found a couple of scripts created by a couple of people over at the uRadMonitor forums for doing exactly this with RRDTool.

Using another Raspberry Pi I had lying around, I’ve implemented these scripts on a minimal Raspbian install, and with a couple of small modifications, the scripts upload the resulting graphs to the blog’s webserver via FTP every minute.

#!/bin/sh

URL=http://192.168.1.4/j
rrdpath="/usr/local/bin"

jsondata=$( curl -s $URL);

v_cpm=$( echo $jsondata | cut -f 4 -d "," | cut -f 2  -d ":" )
v_temp=$( echo $jsondata | cut -f 5 -d "," | cut -f 2  -d ":" )

echo CPM : $v_cpm
echo Temperature : $v_temp

This script just grabs the current readings from the monitor, requiring access to it’s IP address for this.

#!/bin/sh

rrdpath="/usr/bin"
rrddata="/usr/local/urad/data"
rrdgraph="/usr/local/urad/graph"

mkdir $rrddata
mkdir $rrdgraph

   $rrdpath/rrdtool create $rrddata/uRadMonitor.rrd -s 60 \
            DS:cpm:GAUGE:300:0:U   \
            DS:temp:GAUGE:300:-100:100  \
            RRA:AVERAGE:0.5:1:600  \
            RRA:AVERAGE:0.5:6:700  \
            RRA:AVERAGE:0.5:24:775 \
            RRA:AVERAGE:0.5:288:797 \
            RRA:MAX:0.5:1:600 \
            RRA:MAX:0.5:6:700 \
            RRA:MAX:0.5:24:775 \
            RRA:MAX:0.5:288:797
   echo database $rrddata/uRadMonitor.rrd created.

This script sets up the RRDTool data files & directories.

#!/bin/sh

URL=http://192.168.1.4/j
rrdpath="/usr/bin"
rrddata="/usr/local/urad/data"
rrdgraph="/usr/local/urad/graph"
rrdfmt="--font AXIS:6: --font TITLE:9: --font UNIT:7: --font LEGEND:7: --font-render-mode mono --color ARROW#000000 --color GRID#8C8C8C --color MGRID#000000 -v \"cpm\" --alt-y-mrtg --width 600"

jsondata=$( curl -s $URL );

v_cpm=$( echo $jsondata | cut -f 4 -d "," | cut -f 2  -d ":" )
v_temp=$( echo $jsondata | cut -f 5 -d "," | cut -f 2  -d ":" )

echo CPM : $v_cpm
echo Temperature : $v_temp


$rrdpath/rrdtool update $rrddata/uRadMonitor.rrd N:$v_cpm:$v_temp


$rrdpath/rrdtool graph --imgformat PNG $rrdgraph/rad-day.png   --start -86400 --end -600 --title "Radiation daily" $rrdfmt \
        DEF:cpm=$rrddata/uRadMonitor.rrd:cpm:AVERAGE \
                AREA:cpm#00CCCC:"Counts Per Minute\g" \
                        GPRINT:cpm:MAX:"  Max \: %5.1lf " \
                        GPRINT:cpm:AVERAGE:" Avg \: %5.1lf " \
                        GPRINT:cpm:LAST:" Last \: %5.1lf \l"

$rrdpath/rrdtool graph --imgformat PNG $rrdgraph/rad-week.png  --start -604800   -z    --title "Radiation weekly" $rrdfmt \
        DEF:cpm=$rrddata/uRadMonitor.rrd:cpm:AVERAGE \
                AREA:cpm#00CCCC:"Counts Per Minute\g" \
                        GPRINT:cpm:MAX:"  Max \: %5.1lf " \
                        GPRINT:cpm:AVERAGE:" Avg \: %5.1lf " \
                        GPRINT:cpm:LAST:" Last \: %5.1lf \l"

$rrdpath/rrdtool graph --imgformat PNG $rrdgraph/rad-month.png --start -2592000  -z    --title "Radiation monthly" $rrdfmt \
        DEF:cpm=$rrddata/uRadMonitor.rrd:cpm:AVERAGE \
                AREA:cpm#00CCCC:"Counts Per Minute\g" \
                        GPRINT:cpm:MAX:"  Max \: %5.1lf " \
                        GPRINT:cpm:AVERAGE:" Avg \: %5.1lf " \
                        GPRINT:cpm:LAST:" Last \: %5.1lf \l"

$rrdpath/rrdtool graph --imgformat PNG $rrdgraph/rad-year.png  --start -31536000 -z    --title "Radiation yearly" $rrdfmt \
        DEF:cpm=$rrddata/uRadMonitor.rrd:cpm:AVERAGE \
                AREA:cpm#00CCCC:"Counts Per Minute\g" \
                        GPRINT:cpm:MAX:"  Max \: %5.1lf " \
                        GPRINT:cpm:AVERAGE:" Avg \: %5.1lf " \
                        GPRINT:cpm:LAST:" Last \: %5.1lf \l"

$rrdpath/rrdtool graph --imgformat PNG $rrdgraph/rad-decade.png  --start -315360000 -z    --title "Radiation decadely" $rrdfmt \
        DEF:cpm=$rrddata/uRadMonitor.rrd:cpm:AVERAGE \
                AREA:cpm#00CCCC:"Counts Per Minute\g" \
                        GPRINT:cpm:MAX:"  Max \: %5.1lf " \
                        GPRINT:cpm:AVERAGE:" Avg \: %5.1lf " \
                        GPRINT:cpm:LAST:" Last \: %5.1lf \l"
ncftpput -R -v -u "<FTP_USER>" -p "<FTP_PASSWORD>" <FTP_HOST> <FTP_REMOTE_DIR> /usr/local/urad/graph/*

The final script here does all the data collection from the monitor, updates the RRDTool data & runs the graph update. This runs from cron every minute.
I have added the command to automate FTP upload when it finishes with the graph generation.

This is going to be mounted next to the monitor itself, running from the same supply.

The Graphs are available over at this page.

Posted on September 13, 2015September 13, 2015 by The Engineer — Leave a comment

Rigol DS1054Z DC Power Supply – Linear Post Regulation

Finally, here’s the last part of the Rigol 12v DC Power Supply project, the linear post regulation section to remove some of the ripple.

I have made a couple of layout adjustments since the last post about this part of the project – a little more filtering on the DC outputs. As usual the Eagle project files are at the bottom of the post for those who might find them useful.

Here’s the completed PCB, partially installed in the back of the scope. The missing regulator is the 5v one, since I already have a source of clean 5v from my original attempt at the supply, it’s not a problem not using a linear after the switcher. The filtering is the same on all channels, input from the switchers is on the right, outputs to the scope on the left.

Here’s the bottom of the PCB, with the common mode input chokes. The design of this board has allowed me to remove a couple of the switching modules as well, as I can use a single bipolar supply to run both sets of bipolar regulators on this board. This should help remove some of the noise also.

The ripple level has now dropped to lower than it was originally on the mains supply! Current draw at 13.8v DC is about 1.75A.

[download id=”5589″]

Posted on September 2, 2015September 2, 2015 by The Engineer — Leave a comment

Rigol DS1054Z 12v Power Supply Noise Filtering

Since I fitted my scope with a SMPS based 12v input supply, there has been a noise problem on very low volts/div settings, this noise isn’t present on the mains supply, so I can only think it’s coming from the switching frequencies of the various DC-DC modules I’ve used.

Because of this I’ve designed a linear post-regulation stage for the supply, to remove the RFI from the DC rails.
This board takes the outputs from the DC-DC converters, removes all the noise & outputs clean DC onto the mainboard of the scope.

As the scope internally uses regulation to get the voltages lower, I’ve found that I don’t have to match the outputs of the mains supply exactly, for the +/-17.5v rails, 12v is perfectly fine instead.

Here’s the PCB layout, with the 6 common mode filters on the input (left), linear regulator ICs in the centre & the output filters on the right.

Here’s the schematic layout, as usual the Eagle Project files are in the link below, I’ll update when I have built the board & tested!

[download id=”5589″]

73s for now 🙂

Posted on August 26, 2015 by The Engineer — Leave a comment

Rigol 12v Power Supply Project Wiring Loom

As the crimp tool for the PSU connector in the Rigol scope is a very expensive piece of hardware, I decided to use pre-crimped terminals, from an ATX power connector. (They’re the same type).

Here’s the partially completed loom, with the 13 cores for the power rails. The 14th pin is left out as that is for AC triggering, and this won’t be usable on a low voltage supply.
A couple of the pins have two wires, this is for voltage sensing at the connector to compensate for any voltage drop across the cable. The regulators I am using have provision for this feature.

To keep the wiring tidy, I dug a piece of braided loom sleeving out of the parts bin, this will be finished off with the heatshrink once the pins are inserted into the connector shell.
The remaining parts for the loom have been ordered from Farnell & I expect delivery tomorrow.

More to come then!

73s for now 🙂

Posted on August 25, 2015 by The Engineer — Leave a comment

Rigol DS1054Z 12v Conversion Project Update

While searching around for regulators to convert my new scope to 12v power, I remembered I had some DC-DC modules from Texas Instruments that I’d got a while ago. Luckily a couple of these are inverting controllers, that will go down to -15v DC at 15W/3A capacity.

I’ve had to order a new module from TI to do the -17v rail, but in the meantime I’ve been getting the other regulators set up & ready to go.

The DC-DC module I’ve got for the -7.5v rail is the PTN78060A type, and the +7.5v & +5v rails will be provided by the PTN78020W 6A buck regulators.

These regulators are rated well above what the scope actually draws, so I shouldn’t have any issues with power.

Here’s the regulators for the 5v, 7.5v & -7.5v rails, with multiturn potentiometers attached for setting the voltage output accurately. I’ve also attached a couple of electrolytics on the output for some more filtering. I’ll add on some more LC filters on the output to keep the noise down to an absolute minimum. These are set up ready with the exact same output voltage as the existing mains AC switching supply, when the final regulator arrives from TI I will put everything together & get some proper rail readings.

There won’t be a proper PCB for this, as I don’t have the parts in Eagle CAD, and I simply don’t have the energy to draw them out from the datasheets.

More to come when parts arrive!

73s for now 🙂

Posted on August 21, 2015 by The Engineer — 2 Comments

Rigol DS1054Z Power Supply Project

Since everything in my shack is run from 12v, I thought it would be handy to convert my new scope to 12v as well, as 99% of the places I find myself needing test gear are off grid, with no access to mains supplies.

Here’s the factory mains SMPS unit from the back of the scope. This is a nice multi-rail unit, with several different outputs, the table below details the wiring of the PSU.

Connector Pin	PCB Pin	Signal	Measured Voltage	Mainboard	Rectifier Rating	Wire Colour
5	1	AC_TRIG	N/A	AC_TRIG	N/A	BROWN
2	2	+9v_GND	N/A	FAN --	NA	ORANGE
11	3	+9V	10.16V	FAN +	2A	WHITE
6	4	+5V	5.1V	5V5A	20A	RED
13	5	+5V	5.1V	5V5A	20A	RED
7	6	GND	N/A	GND	N/A	BLACK
8	7	GND	N/A	GND	N/A	BLACK
3	8	+7.5V	6.9V	6.3V	20A	YELLOW
10	9	+7.5V	6.9V	6.3V	20A	YELLOW
1	10	GND	N/A	GND	N/A	BLACK
12	11	17.5V	17.51V	17.5V	2A	BLUE
9	12	-17.5V	-17.36V	-17.5V	2A	GREY
14	13	GND	N/A	GND	N/A	BLACK
4	14	-7.5V	-6.84V	-7.5V	2A	GREEN

The only feature I will lose if I make this switch is AC line triggering, but I never use that anyway, so it’s not a big issue for me.

The connector used by Rigol to connect to the mainboard is a Molex Mini Fit Jr. Series 14-way type.

Since I have been able to locate the connector, the plan is to design a replacement low voltage supply unit for the scope, with the same footprint as the original AC mains supply. This will allow me to do a direct swap without causing any damage or modifying the original supply.
This method will allow me to swap the 240v supply back into the scope if I ever come to need it.

I’m planning to use the LTC3863 DC-DC Controller from Linear Tech to generate the negative rails, this will go down to -150v on the output, so it’s pretty much perfect to generate them.

Here’s the output side of the mains PSU, it has a lot of filtering on the output rails, the two TO220 devices are the output rectifiers for the +5v & +7.5v rails, these are rated at 20A, 60V.

Here’s the bottom side of the PCB. It’s a really nicely designed PSU, massive isolation gap, spark gaps on the primary side & good filtering. The output side on the left has the rectifier diodes for the other voltage rails, these are only 2A rated, so designing the inverting supply to generate the negative rails will be pretty easy.

From looking at the PCB markings on both the mainboard & the PSU, the +9v rail seems to be used to drive the fan, both silkscreen markings indicate this.
The voltages marked on the PSU & the mainboard connector don’t quite match up though, there’s a small variation in the stated voltage between the two. This is most likely because all of the regulation of the supplies seems to be done on the mainboard, there are several linear regulators, and a few DC-DC switchers. Providing that the replacement supply isn’t noisy it should work fine.

This is backed up by the fact that the mains PSU only seems to regulate the +5v rail – on measuring the rails that’s the only one that’s close to spec.

Here’s the mainboard power connector, with it’s silkscreen labelling on the pins. (Very useful). As can be seen here, there’s at least 5 regulators, of both switching & linear types here, generating both positive & negative rails.

More to come when I have some components!

73s for now 🙂

Posted on August 12, 2015 by The Engineer — Leave a comment

Chinese 12v 10A Power Brick Analysis

I recently ordered a PSU to run one of the TVs I converted to 12v operation, and being an older TV, it’s a fairly heavy load at 6.5A. eBay to the rescue again, with a cheap 10A rated supply.

Like all similar supplies these days, it’s a SMPS unit, and feels suspiciously light for it’s power rating.

Luckily this one is easy to get into, no ultrasonic welding on the case, just clips. Here’s the top cover removed, big alloy plate between the heatsinks.

The top heatsink plate was glued to the top of the transformer with silicone, some gentle prying released it. From the top, things don’t look too bad. There’s some filtering on the mains input & it’s even fused!

Here’s a closeup of the primary side of the PSU, the main DC bus capacitor is a Nichicon one, but it’s clearly been recovered from another device, look at the different glue on the end!
it’s also flapping about in the breeze, the squirt of silicone they’ve put on does nothing to stop movement.
Also here is the mains input fuse, filter capacitor & common mode choke. At least there is some filtering!

The main control IC is a UC3843B High Performance Current Mode PWM Controller, operating at a switching frequency of 250kHz.
The main switching transistor is visible at the bottom left corner, attached to the heatsink.

Here’s the secondary side of the supply. The transformer itself is OK, nice heavy windings on the output to suit the high current.
It’s using proper opto-isolated feedback for voltage regulation, with a TL431 reference IC.
The output diodes are attached to the heatsink at the top of the photo, I couldn’t read any numbers on those parts.

The output filter capacitors are low quality, only time will tell if they survive. I’ll put the supply under full load & see what the temperature rise is inside the casing.

On the bottom of the PCB things get a little more dire. There isn’t really much of an isolation gap between the primary & secondary sides, and there’s a track joining the output negative with mains earth, which gets to within 2mm of the live mains input!

As with all these cheapo supplies, there’s good points & bad points, I will update when I’ve had a chance to put the supply under full load for a while & see if it explodes!

Posted on August 11, 2015 by The Engineer — 3 Comments

Evolis Dualys3 Card Printer Teardown

I recently dug out my other card printer to fit it with a 12v regulator, (it’s 24v at the moment), and figured I’d do a teardown post while I had the thing in bits.

This is a less industrial unit than my Zebra P330i, but unlike the Zebra, it has automatic duplexing, it doesn’t have Ethernet connectivity though.

Unlike domestic printers, which are built down to a price, these machines are very much built up to a spec, and feature some very high quality components.

Here’s the mechanism with the cowling removed. This is the main drive side of the printer, with the main drive stepper at left, ribbon take-up spool motor lower right, and the duplex module stepper motors at far right.

The main drive motor runs the various rollers in the card path through a pair of synchronous belts, shown here.

The stepper itself is a quality ball-bearing Sanyo Denki bipolar motor.

Electrical drive is provided to the stepper with a L6258EX DMOS universal motor driver. This chip can also drive DC motors as well as steppers.

Here is the encoder geared onto the ribbon supply spool. This is used to monitor the speed the ribbon is moving relative to the card.

Here’s a top view through the printer, the blue roller on the left cleans the card as it’s pulled from the feeder, the gold coloured spool to it’s right is the ribbon supply reel. The cooling fan on the right serves to stop the print head overheating during heavy use.

The spool take-up reel is powered by another very high quality motor, a Buhler DC gearmotor. These printers are very heavily over engineered!
This motor drives the spool through an O-Ring belt, before the gear above. This allows the drive to slip in the event the ribbon jams, preventing it from breaking.

The pair of steppers that operate the duplexing unit are driven by a separate board, with a pair of L6219DS bipolar stepper driver ICs. There are also a couple of opto-sensors on this board for the output hopper.

All the mechanisms of the printer are controlled from this main PCB, which handles all logic & power supply functions. Sections on the board are unpopulated, these would be for the Ethernet interface, smart card programming & magstripe programming.

The brains of the operation is this ColdFire MCF5208CVM166 32-bit microprocessor. It features 16KB of RAM, 8KB of cache, DMA controller, 3 UARTs, SPI, 10/100M Ethernet and low power management. This is a fairly powerful processor, running at 166MHz.
It’s paired with an external 128Mbit SDRAM from Samsung, and a Spansion 8Mbit boot sector flash, for firmware storage.

Here the USB interface IC is located. It’s a USBN9604 from Texas Instruments, this interfaces with the main CPU via serial.

Posted on July 17, 2015July 17, 2015 by The Engineer — Leave a comment

Wouxun KG-UV950P RF Power Measurements

Following on from the earlier power tests on my Baofeng HTs, here’s the readings from the Wouxun KG-UV950P. Power is a little lower than specified, but this is probably due to the supply voltage being a bit less than 13.8v. These readings were taken at a supply voltage of 12.88v.

The same frequencies were used, 145.500 & 433.500 for the VHF/UHF tests. For the 6/10m tests 27MHz & 50MHz were used.
The power meter was connected with 1 metre of RG58 dual-screened cable with N-type connectors.

High

6m: 24W

10m: 23W

VHF: 38W

UHF: 24.9W

Medium-High

6m: 10.9W

10m: 9.3W

VHF: 19W

UHF: 14.2W

Medium-Low

6m: 6.8W

10m: 3.5W

VHF: 9.6W

UHF: 9.4W

Low

6m: 3.5W

10m: 1.9W

VHF: 4.8W

UHF: 4.7W

Posted on July 17, 2015July 17, 2015 by The Engineer — 2 Comments

Baofeng UV-5R RF Power Measurements

I’ve noticed that the RF power output from the Chinese radios can be quite variable from model to model, and even from individual radios of the same model & batch.
I’ve bought an RF Power meter (GY561) to do some tests on the HTs I have at present.

All tests were performed with the radio fully charged & still on the charging base, to make sure the supply voltage remained constant at 8.4v throughout the tests.
Frequencies used were 145.500 & 433.500 for VHF & UHF respectively.
The power meter was connected with ~8″ of RG174 Coax.

High Power:

UV-5R 1 (S/N: 13U1136132):
VHF: 6.3W
UHF: 4.9W

UV-5R 2 (S/N: 13U1136114):
VHF: 6.5W
UHF: 5.2W

UV-5R 3 (S/N: 130U541416):
VHF: 7.1W
UHF: 6.3W

Low Power:

UV-5R 1 (S/N: 13U1136132):
VHF: 2W
UHF: 1.2W

UV-5R 2 (S/N: 13U1136114):
VHF: 2.3W
UHF: 1.5W

UV-5R 3 (S/N: 130U541416):
VHF: 2.7W
UHF: 2.1W

Posted on July 14, 2015July 19, 2015 by The Engineer — 1 Comment

Cisco PSU Hack & Switched Mode PSU Background

Recently I decommissioned some networking equipment, and discovered the power supplies in some switches were single rail 12v types, with a rather high power rating. I figured these would be very good for powering my Ham radio gear.

They’re high quality Delta Electronics DPSN-150BP units, rated at a maximum power output of 156W.

These supplies have an adjustment pot for the output voltage regulation, but unfortunately it just didn’t have quite enough range to get from 12.0v to 13.8v. The highest they would go was ~13.04v.

After taking a look at the regulator circuit, I discovered I could further adjust the output voltage by changing a single resistor to a slightly lower value.

Firstly though, a little background on how switched mode power supplies operate & regulate their output voltage.

Here’s the supply. It’s mostly heatsink, to cool the large power switching transistors.

The first thing a SMPS does, is to rectify the incoming mains AC with a bridge rectifier. This is then smoothed by a large electrolytic capacitor, to provide a main DC rail of +340v DC (when on a 240v AC supply).

Above is the mains input section of the PSU, with a large common-mode choke on the left, bridge rectifier in the centre, and the large filter capacitor on the right. These can store a lot of energy when disconnected from the mains, and while they should have a discharge resistor fitted to safely drain the stored energy, they aren’t to be relied on for safety!

Once the supply has it’s main high voltage DC rail, this is switched into the main transformer by a pair of very large transistors – these are hidden from view on the large silver heatsinks at the bottom of the image. These transistors are themselves driven with a control IC, in the case of this supply, it’s a UC3844B. This IC is hidden under the large heatsink, but is just visible in the below photo. (IC5).

Here’s the main switching transformer, these can be much smaller than a conventional transformer due to the high frequencies used. This supply operates at 500kHz.
After the main transformer, the output is rectified by a pair of Schottky diodes, which are attached to the smaller heatsink visible below the transformer, before being fed through a large toroidal inductor & the output filter capacitors.
All this filtering on both the input & the output is required to stop these supplies from radiating their operating frequency as RF – a lot of cheap Chinese switching supplies forego this filtering & as a result are extremely noisy.

After all this filtering the DC appears at the output as usable power.

Getting back to regulation, these supplies read the voltage with a resistor divider & feed it back to the mains side control IC, through an opto-isolator. (Below).

The opto isolators are the black devices at the front with 4 pins.

For a more in-depth look at the inner workings of SMPS units, there’s a good article over on Hardware Secrets.

My modification is simple. Replacing R306 (just below the white potentiometer in the photo), with a slightly smaller resistor value, of 2.2KΩ down from 2.37KΩ, allows the voltage to be pulled lower on the regulator. This fools the unit into applying more drive to the main transformer, and the output voltage rises.

It’s important to note that making too drastic a change to these supplies is likely to result in the output filter capacitors turning into grenades due to overvoltage. The very small change in value only allows the voltage to rise to 13.95v max on the adjuster. This is well within the rating of 16v on the output caps.

Now the voltage has been sucessfully modified, a new case is on the way to shield fingers from the mains. With the addition of a couple of panel meters & output terminals, these supplies will make great additions to my shack.

More to come on the final build soon!