Controlling 220V ac using 5V analog signal

sorry if i couldnt explain it correctly.

actually we were trying to make a motor speed controller. i was trying to use a sewing machine motor.

i thought of generating an analog signal using a microcontroller and using that signal i wanted to control the amount of voltage that would go to the motor at the end of the day.

in other words i was trying to replace the pedal of the sewing machine by an electric signal.

hopefully it clears up the mess i created above :)

Thanks for your help Phil.

i made a search on the keywords that you recommended and i tried to study the working of the triac in one or two books. But i am getting confused on one point. Can i make a variable speed controller using triacs?

The way i see it, a triac will help me in triggering the motor on but it wont help me in controlling the speed as a "function" of the gate voltage.

sorry...i got the idea.

it has to be dependent upon the width of the gate voltage.

thanks for your help

I don't think you have the right idea... yet. The timing of the trigger pulse in relation to the AC wave is what will control the output. Think about the plain old light dimmer. It controls a light bulb brightness by varying the timing of the triac trigger pulse. The closer the trigger to the start of the AC waveform, the higher the output voltage, thus, the brighter the light. Matter of fact, if a sewing machine motor is what you want to control, a dimmer will probably work just fine. You might want to put a snubber (series resistor/capacitor) across the triac, but I think it would be your simplest solution. I've been using light dimmers to control the speed of ceiling fans for many years.. . never had a failure.

May be you should tell us what you are trying to build. It sounds all too weird....

regards, Wolfgang

What do you mean by controlling? You can turn 220V on and off using a "solid state relay".

Try searching ebay for "crydom solid state relay".

They are very easy to use.

If you want some other kind of control, then it would be interesting to see what.

"shehry"

Try searching Google with "triac" and "phase control".

Also see "opto isolator" & "triac driver ".

......... Phil

a servo-driven Variac would be one way....

smething involving a triac and an optocupler or two might be cheaper. ISTR in the depths of time a colour organ (basically 4 low voltage controlled mains light dimmers) in a Brittish electonics mag, (so 230V but that should be close enough to 220 for practical purp0oses :)

voltage controlled potentiometers that can withstand 220V AV are pretty rare. most are made for around 1V

Bye. Jasen

phase control.... if you trigger the triac late then the motor missess out on some of each half cycle.

what you do is arrange for your microcontroller to get a signal every time the mains changes polarity (aka zero crossing) and then use one of its internal timers to delay some amount of time from getting that signal before triggering the triac.

The longer the delay the slower the motor runs.

I have actually made this very thing! I restored a 1922 Singer machine and cabinet. I used an SCR triggered off the positive peak through a diode and a pot across an RC circuit to trigger the gate (that's the basic of it, I can post the schematic if you need it). This is your basic light dimmer circuit, only they use a triac. I was not interested in speed, or torque at the time the unit was strictly for show. An off the shelf light dimmer should work for you, just make sure the motor is the "Universal" type (has brushes - AC & DC).

Get yourself a module designed to do this. Many will take a 0-10V signal or a pot to control the speed. Make SURE THAT THE INPUT IS GALVANICALLY ISOLATED FROM LINE VOLTAGE.

It takes maybe 50-100 components to do a good job of this-- the modules are relatively cheap, safety-agency approved and work well.

Hi Shehry...

I'm Dwi, a student of Brawijaya University Malang Indonesia.Now I'm trying to build a dimmer which use MOSFET to control the 220 Vac.Have you found the complete circuit?If you have,please help me by sending the circuit to my email account : de snipped-for-privacy@yahoo.com For your concern, Thank you very much.