How to quickly find out the speed of an electric motor without a sign and disassembly

Often you have to deal with old electric motors that do not have labels with characteristics of power, speed, etc. Such an electric motor can be used as a drive. For example, when making emery, an engine of 3000 rpm is required, because at lower speeds the wheel is intensively chipped.

How to determine engine speed using a smartphone

Modern high technologies will help you set the rotation speed of the electric motor shaft. You need to download the free application “Strobe RPM Tachometer Lite” from Google Play, based on the strobe effect.

The phone screen shows the rotation speed (revolutions), buttons for turning on and off, increasing and decreasing the rotation speed. In fact, an application with specified parameters controls the blinking frequency of the light source (flashlight) on the phone.

Next, we apply a mark in the form of a clear (contrasting) line in the radial direction on the tool (disk) mounted on the motor shaft. It is advisable that the mark be applied as far as possible from the center of the shaft. This ensures measurement accuracy.

Then we turn on the electric motor and direct the blinking light source to the mark, changing its frequency, both up and down using the corresponding buttons on the phone screen.

You need to achieve a state where the mark on the disk seems to freeze in place. The rotation speed that will be displayed at this moment on the phone screen will be the number of engine revolutions per minute.

In our case, the mark freezes at 1500 rpm. This is the true speed of the electric motor shaft. If you set a higher frequency on your phone, the label begins to rotate in the opposite direction and vice versa.

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