“A small voltmeter that sits on a breadboard’s power rails
I wanted to try out the ATtiny85 and get some practice hand-soldering QFN components, so I built a basic voltmeter that sits on the power rails of a breadboard.
Displays power supply voltage, rounded to the nearest volt_
_ Reversible - cannot be inserted incorrectly
Low power consumption - below 3mA_
_ Small - only takes up a single 2x5 block of pins on a standard breadboard power rail
Some things I’d do differently next time:
Include a programming header for the ATtiny85. I had to solder it some 30 awg wire-wrap wire to existing PCB pads to program the ATtiny before adding any other components.
Use regular 0603 resistors instead of a resistor network. I ended up ordering the wrong size network and had to use discrete resistors anyway.
Show non-integer voltages by adjusting the relative brightness of adjacent LEDs.
Indicate voltages above 12V or below 3V by flashing the 12V / 3V LEDs.
Make it even smaller by using 0.8mm thick PCBs instead of 1.6mm.”