How Can I Use an Arduino with an LCD to Display a Motor's Speed?

This article will guide you through the process of utilizing an Arduino and an LCD display to monitor and display the speed of a motor. We will break the problem into two main parts: measuring or computing the motor's speed and displaying this information on the LCD.

1. Measure/Compute Motor Speed

The first step is to determine the method you will use to compute or measure the motor's speed. Depending on the type of motor you are working with, you may need different methods. For example, when using a PWM (Pulse Width Modulation) control or V-by-f (Volts-per-Radians-per-Second) control for induction motors, you can estimate the motor speed based on the system's duty cycle or frequency. However, for a more precise measurement, it is recommended to use rotary position sensors or Hall effect sensors.

Example Methods:

Arduino Playground - Reading RPM Arduino Playground - Motor RPM Measurement Using Hall Effect Sensor

2. Display Motor Speed on an LCD

The second part involves updating the LCD display with the motor speed data. This is a simple process of sending the updated information to the LCD display function. You can find more detailed information about this process in the Arduino HelloWorld tutorial.

Perhaps the result you can achieve will look something like this:

Motor Speed Tester Using Arduino and IR Sensor

Note: For simplicity, I have included links to Arduino resources. However, any microcontroller can be used for similar functionality. It's essential to ensure that the error in estimated speed is minimized with the use of proper sensors.

Motor Speed from Nameplate Information

In most cases, the motor's speed is already indicated on the nameplate. For example, a motor with a nameplate indicating a speed of 975 RPM runs on a 50Hz 3-phase supply, implying it has 3 pole pairs per phase and runs at a slip of 25 RPM or 0.42 Hz at the rated load of 10 HP. If you are interested in the slip, it is typically load-dependent, and the cheapest way to determine it is by measuring the current with a clamp-on multimeter. Under normal operating conditions, the slip is approximately proportional to the current drawn, which is sufficient for most industrial applications. Better accuracy can be obtained using a calibrated graph of motor speed versus current.

Using Hall Effect Sensors for Speed Measurement

One practical method to measure motor speed is to attach a Hall effect sensor to a rotating component of the motor, such as a spoke or rotor. The sensor will trigger each time it passes a magnet. By counting these triggers over a second, you can calculate the motor's speed.

For interfacing with an LCD, especially if you are using a Phillips HD44780 driver, it's straightforward to use Arduino's built-in Liquid Crystal library to communicate with the display. Refer to the Arduino Liquid Crystal tutorial for more details.

By following the steps outlined in this guide, you can successfully monitor and display the motor's speed using an Arduino and an LCD display. Remember to choose the appropriate method for your specific motor type and application to ensure accurate and reliable results.