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Multi Purpose Rotary Machine - Mulling, Welding, Pottery, Photography Turntable

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Step 16: Motor Control #2: the Simple Way

Picture of Motor Control #2: the Simple Way
Motor Speed control with DC section.jpg
additional-transformer motor speed control.jpg

These are some simple universal motor control circuits that I have made in the past. They are based about a power triac (T1) that is triggered by a diac (D1). This kind of circuit is simple and time proven. Historically versions of this circuit have been used to control many different universal motors, from circular saws to vacuum cleaners.

I have used these circuits in the past on my lathe instructable here, so I'm not going to go re-hash that info in much detail here (check out steps 2 to 6 on that I'ble) .

The first schematic shows the most basic of these circuits, the second and third add in a rectified, low voltage, high current stage, that gives the motor much better speed holding under loads (it won't slow down so much when you put load on the motor).

This documents some further Improvements to this circuit, using a smaller triac to trigger the main one:

There is a lot to be said for the simplicity of this circuit, and if I was doing this project over, I might consider doing another one of these Vs the closed loop arduino version I made.