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Topic: controlling the AC MOTOR of a SUPER 8 projector through the arduino PWM (Read 1 time) previous topic - next topic


hi everyone,

wondering if i could get some help with my little project.
i would like to control the speed of my super 8 projector with the PWM output of my Arduino.
here are some specs written on the back of my projector:

volts: 240 V
Watts 130W
A.C. 50.60 Hz
LAMP 8v 50W

After some initial research i've built a little test circuit that succesfully powers a little D.C. motor (salvaged from a cassette player) from my arduino uno.
The circuit i used is from this youtube tutorial (http://youtu.be/hcpqt-BREqI) but instead of the a potentiometer, i am using a PWM output from the arduino (controlled by max/msp) and  instead of the transistor
i am using a power Mosfet. this one in particular http://www.rapidonline.com/Electronic-Components/Stp4nk80z-Mosfet-To-220-800v-3a-47-0190. I was told this would be essential to handle the 240V mains going through the projector.
but for now the power source i used for this test setup is a 9v battery.

I am now about to test this setup with the A.C. motor of my projector (instead of the little D.C. motor) and the 240V mains (instead of the 9V battery)  before I do so I wanted to know the following things:

- for safety reasons, should i have an optical isolator somewhere in my circuit?
- Is there any difference in controlling the voltage of D.C. motor and an A.C. motor?
- Is there any essential components I am missing in my setup ?

If i am completely wrong, feel free to suggest me a better circuit for my setup.
Thanks a mill!


If it's an AC Motor then you cannot use a FET, you need a TRIAC.
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!


Step away from the mains.

Your Arduino PWM almost certainly will not work.
Your best bet is to use a triac-based speed controller, but you're really not ready to go there yet.
Please, don't risk anything until you know what sort of motor is used.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.
I speak for myself, not Arduino.


I was told this would be essential to handle the 240V mains going through the projector.

Do you know many more idiots as well as that one.

Any mains controller has to be optically isolated.
You can't control the speed of an AC motor with PWM.

If you don't know this you are not ready to play with mains.


Its absolutely critcal to know what sort of AC motor the projector uses as this determines how to control its speed.
It could be a universal type of motor which has brushes and will run on AC or DC, or the more common capacitor start
induction motor which cant be easily speed controlled.

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