A needle sweeping across a printed dial beats a touchscreen when your hands are covered in flour. Michał Zalewski built exactly that: a kitchen timer called Burninator that drives a salvaged Crompton panel meter from a tiny AVR microcontroller.
An old current meter becomes the display
The dial started life measuring electrical current in industrial gear. Zalewski kept the movement, peeled off the original markings, and stuck on a custom scale printed on adhesive paper. The scale is quasi-logarithmic, split into four zones: up to 1 minute in 10-second steps, 1 to 5 minutes, 5 to 30 minutes, and out to 3 hours. Short timers get fine resolution, long ones get coarse steps, and a single knob covers everything. Details are in the Hackster write-up.
How the electronics work
An 8-bit AVR DB-series chip handles timing and moves the needle with PWM. A panel meter is just a coil that responds to average current, so changing the duty cycle changes the deflection. A low-pass filter or a series resistor smooths the pulses so the needle does not twitch. The alarm goes through an AD8531 op-amp to a small speaker, a Bourns rotary encoder sets the time, and the whole thing runs from a 5 V adapter inside a maple enclosure.
The behavior is where the design shines. The countdown starts 3 seconds after your last knob turn, you can adjust it mid-run, and the alarm repeats every 15 seconds until you press the illuminated button. Turning the knob clockwise to add time also silences it.
Build it yourself
You do not need a vintage meter to try the idea. Use an Arduino Uno or Nano, a 0 to 1 mA analog panel meter, and a 4.7k resistor in series on a PWM pin such as D9. Write a lookup table in code that maps encoder detents to needle positions, then calibrate each zone against a stopwatch and print the scale on paper. A rotary encoder with a push switch and a small piezo buzzer cover the rest. It makes a tidy mini-project for an embedded systems class, and you can compare the PWM approach with a DAC or an MCP4725 breakout. Find Arduino boards and encoders at Circuit.Rocks.
Frequently Asked Questions
How does Burninator move the needle?
An AVR DB-series microcontroller outputs a PWM signal to a repurposed Crompton panel meter. Changing the duty cycle changes the average current, which sets how far the needle swings.
What parts would I need for a copy?
An Arduino Uno or Nano, a small analog panel meter, a rotary encoder, a piezo buzzer or speaker, a push button, and a series resistor. Paper and a printer handle the custom dial scale.
What will I learn if I build this?
You will learn PWM output, reading a rotary encoder with debounce, building a nonlinear lookup table, and calibrating an analog instrument against a reference clock.
