Component/Transistor tester based on famous AVR Transistor Tester project. The reason I decided to create a custom PCB is that currently there is not good kit or complete device available that would fit my wishes:
- ATMega644 MCU
- 2.4" 65K colors LCD
- Rotary encoder
- USB-C charger with Li-Po battery
- Higher grade/precision components
Most of Chinese versions are starting to use fake or non-original Microchip MCUs that prevents their software upgrades and economy on components makes them less accurate. I didn't include a lot of hardware options, because I primarily using the device for measuring passive components and transistors used in guitar pedals building.
I used SMD assembly service at JLCPCB and ended up with a set 5 PCBs cost around 25$ each. But since SMD components used there is not the smallest size ones, it is 100% possible to solder everything by hand.
PCB has almost everything as SMD assembly and requires a few components to be soldered by hand:
- Rotary Encoder - basically any common one would work here, but I've used BOURNS PEC11R-4220K-S0024. It is available at most big components suppliers. My personal choice was TME.
- ZIF 14 pin socket - again you could use any common one. I used CONNFLY DS1044-140G from TME
- 2.4" 65K colors LCB. Not sure if other ILI9341 controller based would have the same pins/size. I used Waveshare 18366 which is not expensive and commonly available. At TME too ;)
- 2.54mm spaced 2x3 pins for ISP - this could be left without pins soldered, then just ensure you have good contact between the PCB and programming pins.
- 2.54mm 3 pin socket for components/transistors - just alternative for ZIF socket
- Any Li-Po or Li-Ion battery with work with the charger IC, but the PCB was designed with Li-Po in mind due to size. I used 550mA battery, but you could use any other that would fit about 55x50mm size.
The software used in m-software version 1.53m (see docs), but k-software could be used as well. The pins assignment is based on project docs suggested one. Precompiled version is in the software folder.
- Install AVR tools for your operating system and programmer you are using (ex. avrdude)
- Navigate to software folder
- Run
make - Connect programmer to the ISP pins on the PCB
- Run
make fusesto set MCU fuses - Run
make uploadto upload firmware
I designed a simple 3D printable enclosure that fits the PCB and provides easy access to ISP pins and USB-C charger. STEP files are located in the 3d-enclosure folder. Printing profile is available at MakerWorld which would be handy if you have a BambuLab 3D printer.
The assembled PCB with display is mounted to enclosure using spacers that came with Waveshare display using 4 x M2x8mm and 4 x M2x16mm screws. the battery is fixed on the backplate with double sided 3M foam.