Learning PI control with Arduino: tachometer signals and response

Original material: 2015-02 · Article edited: 2026-09-08

Adapted from Yoshinobu Tanno’s published slides with AI assistance. Historical implementation details are distinguished from added explanations.

Read the original slides: PI制御を作ってみた

A motor and a tachometer make feedback visible: change a target, then observe how the measured signal approaches it. “The motor runs” is only the first checkpoint.

A teaching apparatus

The February 2015 slides describe an Arduino Mega 2560, two coupled small motors, and a FET drive circuit. One motor is driven; the other provides a tachometer voltage. MATLAB 2014b and Simulink were used to view the target and response. Original slides, 2–7.

Separate three signals

Reference r: the desired value, expressed on a scale comparable to the measurement.
Measurement y: the tachometer feedback.
Control output u: the drive command calculated by the controller.

The error is e = r − y. Proportional action responds to the present error; integral action accumulates error. The reference is not the controller's drive output.

Read the response

The slides show step tracking, not a quantitative validation of settling time or accuracy. For a new classroom comparison, record rise behavior, overshoot, oscillation, and remaining offset. Keep the target and sample interval fixed while changing one gain. If the actuator saturates, inspect output limiting and integral accumulation as well. These are additional observation prompts, not reported experimental results.

Mechanical and electrical details matter

The original Q&A identifies stable motor mounting as a practical difficulty. Also, tachometer voltage requires calibration before it can be reported as rotational speed.

On the Mega, a PWM analogWrite output is not a constant analog voltage. Drive a motor through an appropriate circuit, not directly from a GPIO. Arduino reference.

How to use this record

Use it to plan demonstrations and distinguish mechanical, electrical, and software issues. Prices and software details belong to 2015. A circuit figure cites a textbook; that figure is not reproduced here.