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Dyson DC35 “Digital” Teardown

DC35
DC35

Here’s another Dyson teardown, in my efforts to understand how marketing have got hold of relatively simple technology & managed to charge extortionate amounts of money for it.
This is the DC35, the model after the introduction of the brushless digital motor.

Back Cap Removed
Back Cap Removed

On this version the mouldings have been changed, and the back cover comes off, after removing the battery retaining screw. It’s attached with some fairly vicious clips, so some force is required. Once the cap is removed, all the electronics are visible. On the left is the motor itself, with it’s control & drive PCB. There’s another PCB on the trigger, with even more electronics. The battery connector is on the right.

Trigger PCB
Trigger PCB

Here’s the trigger PCB, which appears to deal with DC-DC conversion for powering the brush attachments. The QFN IC with yellow paint on it is an Atmel ATTiny461 8-bit microcontroller. This is probably controlling the DC-DC & might also be doing some battery authentication.

"Digital Motor"
“Digital Motor”

Here’s the motor & it’s board. The windings on the stator are extremely heavy, which makes sense considering it’s rated at 200W. The main control IC is a PIC16F690 from Microchip. Instead of using an off the shelf controller, this no doubt contains software for generating the waveforms that drive the brushless motor. It also appears to communicate with the other PCBs for battery authentication.

Stator
Stator

Desoldering the board allows it to be removed from the motor itself. The pair of windings are connected in anti-phase, to create alternating North-South poles depending on polarity. Since the existing controller is unusable due to software authentication with the other parts, I might have a go at building my own driver circuit for this with an Arduino or similar.

Blower Assembly
Blower Assembly

The blower assembly is simple plastic mouldings, pressed together then solvent welded at the seam.

Impeller
Impeller

The impeller is just a centrifugal compressor wheel, identical to what’s used in engine turbochargers.

Motor Control Board
Motor Control Board

The inside face of the control PCB holds the 4 very large MOSFETs, IRFH7932PbF from International Rectifier. These are rated at 30v 20A a piece, and are probably wired in a H-Bridge. There’s a bipolar Hall switch to sense rotor position & rotation speed, and an enormous pair of capacitors on the main power bus.

Motor Control Board Reverse
Motor Control Board Reverse

Not much on the other side of the PCB other than the microcontroller and associated gate drive stuff for the FETs.

Battery Pack Opened
Battery Pack Opened

The battery pack is similar to the DC16 in it’s construction, a heavily clipped together plastic casing holding 6 lithium cells. In this one though there’s a full battery management system. The IC on the top of the board above is a quad Op-Amp, probably for measuring cell voltages.

Battery BMS Bottom
Battery BMS Bottom

The other side of the BMS board is packed with components. I wasn’t able to identify the QFN IC here, as it’s got a custom part number, but it’s most definitely communicating with the main motor MCU via IĀ²C over the two small terminals on the battery connector.

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12v Temperature Controlled Soldering Iron

In my shack, 99% of my gear is all 12v powered, which is good for a few reasons:

  • Single Power Supply – This increases efficiency, as I’m only getting the losses of a single supply.
  • Safety – Mains voltages are dangerous, I’m not fond of working on such equipment.
  • Portability – I can power everything pretty much no matter were I am from a convenient car battery.
  • Convenience – Since everything is single supply, with all the same plugs, I don’t have to think about what goes where. This is more important due to my forgetfulness ;).

The one piece of equipment I regularly use that isn’t 12v is my soldering station. This is a Maplin A55KJ digital unit, which uses a 24v heating element.
While the soldering wand works OK when hooked direct to a 12v power supply (only at half power though), this removes the convenience of having temperature control.

The circuitry inside the unit is PIC microcontroller based, and doesn’t even bother rectifying the AC from the supply transformer before it’s sent to the heater. Because of this there are several reasons why I can’t just hook a DC-DC converter up to it to give it 24v.

It’s sensing the zero-crossing for the triac switch, to reduce heat dissipation, so it refuses to work at all with DC.

On looking at the Great Google, I found a project on Dangerous Prototypes, an Arduino based PID controller for soldering irons.

This requires that the soldering wand itself contains a thermocouple sensor – as the Maplin one I have is a cheap copy of the Atten 938D, it doesn’t actually use a thermocouple for temperature sensing. It appears to read the resistance of the element itself – Nichrome heating elements change resistance significantly depending on temperature.

I’ve managed to find a source of cheap irons on eBay, with built in thermocouples, so I’ve got a couple on order to do some testing with. While I wait for those to arrive, I’ve prototyped up the circuit on breadboard for testing:

Prototype
Prototype

I’ve remapped some of the Arduino pins, to make PCB layout less of a headache, but the system is working OK so far, with manual input for the sensed temperature.
I’m using an IRL520N logic-level HEXFET for the power switching, rated at 10A. As the irons only draw a max of 4.5A, this is plenty beefy enough.
To come up with the +24v supply for the heater, a small DC-DC converter will be used.

More to come when the components for the thermocouple amplifier arrive, and the soldering irons themselves!

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Arduino SWR Power Meter Final Parts & Calibration

Now the final bits have arrived for the SWR Meter module, I can do the final assembly.

SMA Connectors
SMA Connectors

Here the SMA connectors are installed on the side of the eBay meter, for forward & reverse power tap.
These are simply tee’d off the wiring inside the meter where it connects to the switch.

Uncalibrated
Uncalibrated

The meter is connected to the module via a pair of RG58 SMA leads, above is a readout before calibration, using one of my Baofeng UV-5Rs.

I’m using my GY561 eBay Power Meter as a calibration source, and as this isn’t perfect, the readings will be slightly off. If I can get my hands on an accurate power meter & dummy load I can always recalibrate.

Tools are only as accurate as the standard they were calibrated from!

After calibration, here’s the readings on 2m & 70cm. These readings coincide nicely with the readings the GY561 produce, to within a couple tenths of a watt. SWR is more than 1:1 as the dummy load in the GY561 isn’t exactly 50Ī©.

High Power VHF
High Power VHF
Low Power VHF
Low Power VHF
High Power UHF
High Power UHF
Low Power UHF
Low Power UHF

Shortly I’ll calibrate against 6m & 10m so I can use it on every band I have access to šŸ™‚