Transistor Tester Becomes Car Display

These days, the electronics hobbyist is lucky to have access to a wide range of ready-made modules that enable sensors, screens, and microcontrollers to all be linked up with ease. However, this manner of working generally ends up with a project that becomes more of a PCB salad than a finished product. Oftentimes, it’s possible to find something off the shelf that’s close to your requirements, and repurpose it to work. That’s exactly what [Aaron] did.

[Aaron] wanted to install a display in his classic Jeep to display the time and some basic parameters. A screen and a microcontroller were called for, and a cheap open-source transistor tester had exactly that already. Consisting of an ATmega-328P linked up to an 128 x 64 graphic LCD module, it had most of what [Aaron] needed from the get go.

To repurpose the device, [Aaron] started by swapping the 8 MHz crystal for a 16 MHz one to make it more easily programmable through the Arduino IDE. Then, a custom firmware was written, which communicates with a DS3232 real time clock, temperature and pressure sensors, and also monitors battery voltage. It’s all neatly installed in the vehicle behind a 3D printed faceplate, and the graphic LCD is clear and easy to read – if you speak German.

[Aaron] has helpfully outlined the various online resources that helped with the hack, including the transistor tester schematic. Our very own [Adam Fabio] reviewed these units in 2015.

If you’ve cleverly reused some existing hardware yourself, be sure to let us know on the tip line. Video after the break.

11 thoughts on “Transistor Tester Becomes Car Display

  1. That’s a pretty good way to get one of those matrix lcd screens for cheap + you get all the extra supporting circuitry for free. They don’t really sell those screens on Aliexpress, not for that price anyway. Good stuff

  2. A better schematic of the transistor tester is on the github repo from Upcycle-Electronics:
    https://github.com/Upcycle-Electronics/AVR-Transistor-Tester/blob/master/Final%20Draft%20LCD%20Master%20Transistor%20Tester.pdf

    That schematic has 20+ different LCD’s, from 2×16 HD44780 to full color TFT’s and probably also has software to match it.

    As uC+ display I’m more interested in buying a few DSO-138’s or “DSO shell” for the STM32F103 + TFT even though the display is rather small. Found some references on stm32duino of peaople who already did this.
    The STM32 has enough horses to power such a display properly, and development kits with PCB + uC +TFT for the STM32 tend to cost more than EUR40 on Ali.

    1. Some while back I bought a Chinese ‘intelligent uart display’ that had a STM32F0 on it, for under £10. Can’t remember the details (nor find the board!) right now – I’ll look this evening

      1. The “Nextion” displays from Ali / Ebay / China seem to have an STM32F030 on them. Prices for the small displays start around EUR15. I’m not sure how many unused pins they have to add your own hardware.

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