This project is an expansion board PCB for a cheap electronic component tester. There are many variants of this device on Ali Express. I based my board on this one: GM328A V1.11
Expansion board features:
Li-PO battery replaces 9V battery.
1 cell Li-PO charger with micro USB connector.
Adjustable low battery voltage indicator.
PCB designed with KiCAD. All project files are on GitHub
Step 1: Schematic
Schematic consists of three parts:
- LiPO battery charger.
- Low battery voltage indicator.
- Voltage BOOST converter.
Charger based on MCP73831 integrated charge management controller. Max charging current is set to 500 mA by R1 and R2. Indicator LED turns on when battery is fully charged. Power input for charger is 5V from micro USB connector.
Low battery voltage indicator LED turns on when voltage on Q1 base reaches threshold which is set by R4, R5, R6, RV1, R7 voltage divider. With given values LED turns on when battery voltage drops to ~3.8V, threshold can be adjusted with RV1 potentiometer.
Voltage BOOST converter circuit is based on MCP1661 IC. Output voltage is set with R10 R11 voltage divider, with given values output voltage will be around 8.8V.
Step 2: PCB
PCB designed with KiCAD. I mostly used SMD parts (0805, 1206, SOT-23 ). PCB size is 75x72 mm. Board pictures is from REV A, gerber files from REV B. I removed ICSP connector from REV B which initially was placed with idea to pass 5V directly to MCU from micro USB. This didn't work because there was now way to reset MCU to check component again. Other differences from REV A is small tweaks of the layout and silkscreen.
Boards were made by PCBWay.
Step 3: Assembly
For battery I used a small Li-PO from Syma X5C quad-copter. Battery is hold in place by wires soldered to bottom side of the PCB.
Original component tester 9V connector should be replaced by standard 2pin female connector.