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eBay Reverse Parking Sensors Teardown

Parking Sensors Kit
Parking Sensors Kit

This is a cheap kit from eBay, to retrofit an older car with ultrasonic parking sensors. 4 sensors are included in the kit, along with a hole saw to fit them to the bumper. There’s a small controller module, and a display module that fits onto the dash of the car.

Controller Module
Controller Module

Here’s the controller module, with it’s row of connectors along the front. The unit gets it’s power from the reversing light circuit, via the red connector.

Main Controller PCB
Main Controller PCB

Removing a couple of screws allows the PCB to be removed. There’s quite a bit on this board, including 4 tunable inductors for the ultrasonic transducers. There’s a linear voltage regulator on the left which supplies power to the electronics, and a completely unmarked microcontroller.

Electronics Closeup
Electronics Closeup

A closer look at the analogue end of the board shows a JRC4558D dual Op-Amp, and an NXP HEF4052B analogue multiplexer. As the microcontroller is unmarked I have no data for that one.

Dash Display
Dash Display

The dash display is housed in another small plastic box, with bargraphs for each side of the car & an overall distance meter.

Display Module
Display Module

Clearly this is a custom module, with the tapered bargraph LEDs on each side & the 7-segment display in the centre. There’s a beeper which works like every factory-fitted unit does, increasing in rate as the distance closes.

Display PCB
Display PCB

The back of the display module has the driver PCB, with yet another unmarked microcontroller, and a TI 74HC164 serial shift register as a display driver. There’s only 3 wires in the loom from the controller, so some sort of 1-wire protocol must be being used, while I²C is the most likely protocol to be talking to the display driver circuit. There’s also a small switch for muting the beeper.

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First Alert CO-FA-9B Carbon Monoxide Alarm Teardown

CO-FA-9B Alarm
CO-FA-9B Alarm

Here’s another domestic CO Alarm, this one a cheaper build than the FireAngel ones usually use, these don’t have a display with the current CO PPM reading, just a couple of LEDs for status & Alarm.

Rear
Rear

This alarm also doesn’t have the 10-year lithium cell for power, taking AA cells instead. The alarm does have the usual low battery alert bleeps common with smoke alarms though, so you’ll get a fair reminder to replace them.

Internals
Internals

Not much at all on the inside. The CO sensor cell is the same one as used in the FireAngel alarms, I have never managed to find who manufactures these sensors, or a datasheet for them unfortunately.

PCB Top
PCB Top

The top of the single sided PCB has the transformer for driving the Piezo sounder, the LEDs & the test button.

PCB Bottom
PCB Bottom

All the magic happens on the bottom of the PCB. The controlling microcontroller is on the top right, with the sensor front end on the top left.

Circuitry Closeup
Circuitry Closeup

The microcontroller used here is a Microchip PIC16F677. I’ve not managed to find datasheets for the front end components, but these will just be a low-noise op-amp & it’s ancillaries. There will also be a reference voltage regulator. The terminals on these sensors are made of conductive plastic, probably loaded with carbon.

Sensor Cell & Piezo Disc
Sensor Cell & Piezo Disc

The expiry date is handily on a label on the back of the sensor, the Piezo sounder is just underneath in it’s sound chamber.

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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.