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Silverline Polisher Fail

Commutator
Commutator

Since I seem to be the local go-to for any dead electrical equipment, this brand-new Silverline polisher has landed on my desk. Purchased cheap from an auction this was dead on arrival. Checking the fuse revealed nothing suspect, so a quick teardown to find the fault was required.
Above is a photo of the commutator with the brush holder removed, and the source of the issue. The connection onto the field winding of the universal motor has been left unsecured, as a result it’s managed to move into contact with the commutator.
This has done a pretty good job of chewing it’s way through the wire entirely. There is some minor damage to the commutator segments, but it’s still smooth, and shouldn’t damage the brushes.

Chewed Wire
Chewed Wire

A quick pull on what’s left of the wire reveals the extent of the problem. It’s entirely burned through! Unfortunately the stator assembly with the field windings is pressed into the plastic housing, so it’s not removable. An in-place solder joint was required to the very short remains of the wire inside the housing. Once this was done the polisher sprang to life immediately, with no other damage.
This unit probably ended up at an auction as a factory reject, or a customer return to a retail outlet. If the latter, I would seriously question the quality control procedures of Silverline tools. ๐Ÿ˜‰

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Contec CMS-50F Pulse Oximeter Teardown

Rear Case
Rear Case

The rear has the specifications, laser-marked into the plastic. The serial numbers are just sticky labels though, and will come off easily with use.

Contec CMS-50F
Contec CMS-50F

This is the Contec CMS-50F wrist-mounted pulse oximeter unit, which has the capability to record data continuously to onboard memory, to be read out at a later time via a USB-Serial link. There is software supplied with the unit for this purpose, although it suffers from the usual Chinese quality problems. The hardware of this unit is rather well made, the firmware has some niggles but is otherwise fully functional, however the PC software looks completely rushed, is of low quality & just has enough functionality to kind-of pass as usable.

Top Cover Removed
Top Cover Removed

A total of 4 screws hold the casing together, once these are removed the top comes off. The large colour OLED display covers nearly all of the board here. The single button below is the user interface. The connection to the probe is made via the Lemo-style connector on the lower right.

Lithium Cell
Lithium Cell

Power is provided by a relatively large lithium-ion cell, rated at 1.78Wh.

Main Processor
Main Processor

All the heavy lifting work of the LCD, serial comms, etc are handled by this large Texas Instruments microcontroller, a MSP430F247. The clock crystal is just to the left, with the programming pins. I’m not sure of the purpose of the small IC in the top left corner, I couldn’t find any reference to the markings.

Aux Processor
Aux Processor

The actual pulse oximetry sensor readings seem to be dealth with by a secondary microcontroller, a Texas Instruments M430F1232 Mixed-Signal micro. This has it’s own clock crystal just underneath. The connections to the probe socket are to the right of this ยตC, while the programming bus is broken out to vias just above. The final devices on this side of the board are 3 linear regulators, supplying the rails to run all the logic in this device.

Main PCB Rear
Main PCB Rear

The rear of the PCB has the SiLabs CL2102 USB-Serial interface IC, the large Winbond 25X40CLNIG 512KByte SPI flash for recording oximetry data, and some of the power support components. The RTC crystal is also located here at the top of the board. Up in the top left corner is a Texas Instruments TPS61041 Boost converter, with it’s associated components. This is probably supplying the main voltage for the OLED display module.

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EpEver MT50 Control Panel Teardown

MT50 Control Panel
MT50 Control Panel

Here’s the MT50 controller from EpEver, that interfaces with it’s Tracer MPPT solar charge controllers, and gives access to more programming options on the charge controllers, without the need for a laptop. The display is a large dot-matrix unit, with built in backlight. Above is the display on the default page, showing power information for the entire system.

PCB Rear
PCB Rear

The rear plastic cover is held in place by 4 machine screws, which thread into brass inserts in the plastic frame – nice high quality touch on the design here, no cheap self tapping plastic screws. Both power & data arrive via an Ethernet cable, but the communication here is RS-485, and not compatible with Ethernet! The PCB is pretty sparse, with comms & power on the left, LCD connection in the centre, and the microcontroller on the right.

RS-485 Transceiver
RS-485 Transceiver

On the left of the board is the RS0485 transceiver, and a small voltage regulator. There’s also a spot for a DC barrel jack, which isn’t included in this model for local power supply.

STM32 Microcontroller
STM32 Microcontroller

The other side of the board holds the main microcontroller which communicates with the charge controller. This is a STM32F051K8 from ST Microelectronics. With a 48MHz ARM Cortex M0 core, and up to 64K of flash, this is a pretty powerful MCU that has very little to do in this application.

PCB Front
PCB Front

The front of the PCB has the ENIG contacts of the front panel buttons, and the LCD backlight assembly. There’s nothing else under the plastic backlight spreader either.

LCD Rear
LCD Rear

The front case holds the LCD module in place with glue, and the rubber buttons are placed underneath, which is heat staked in place.

LCD Model
LCD Model

The LCD is a YC1420840CS6 from eCen in China. Couldn’t find much out about this specific LCD.