In the old days, the mechanical teletype devices have a regulated electric motor with stroboscope markings. The motor speed must be well-trimmed to get the correct baud rate for communication. The tuning was done with a mechanical fork with windowed sheets at the end. A technician looks through the fork windows to see the motor marking interfering.
The fork oscillates with 125Hz which gives a shuttering frequency of 250Hz.
In this project an Arduino-Nano-based stroboscope gives pulses with 250Hz and 10 % duty cycle to let a LED flicker.
Mechanical teletypes have black and white markings at the motor axis. These markings are designed to interference with 250Hz (typical 1500rpm and 10 markings).
Dim the room light and lit the markings with the Strobo-LED. If the motor speed is perfectly adjusted, the marking looks to stand still.
Designed for an Arduino Nano (or any other Arduino with AVR ATmega328).
Use an ultra-bright white LED and connect it between Arduino pin D3 and GND with a serial resistor of 47 Ohm. The AVR can source up to 40mA per pin.
The LED shows NOT the full light to human eyes because the PWM pulses the LED with a duty cycle of 10%. Accuracy is adequate.
Accuracy is adequate.
The Arduino Nano is glued on a cheap torch light with three AAA batteries. The battery voltage is between 4.5V and 3V (empty) and fits the spec of the AVR chip. An additional NPN-transistor (BC337) is used to switch the 200mA from the 1Watt LED.
