120v 1.5a pulser?

Question

Not sure if that's what you call it. Maybe you can just tell me the name for the type of control so I can search to learn more about it if you don't have time to read all this and help me understand it. My electronics teacher should know but I don't want to rely on him for my own project I'm presenting... This my first year in 10th grade H.S. and we have to come up with something before the end of the semester that we come up with to make use of basic electronics. Well my idea isn't so basic. I want to take a 120 volt 1.5 amp motor and cause it to run in a pulse pattern. In other words, it switches on for a second or two, just long enough to get it turning, then off for the same time frame (adjustable?) and back on the same way over and over. I want this to be readily capable of pluging in-line to where I could add it to anything I wanted temporarily.

What I hope to accomplish is a very very low speed for a fan for the sake of non-intrusive room aerating with a window fan, while also having the ability to switch it off, or bypass it to use normal settings.

I wonder if this will damage the fan... perhaps shorten the life of the coil wire or brushes if there are any... and overhead after a while because of the extra amperage that would be encouraged to push it at repeated start-ups... well;. that's what testing and finding out will show.

Can someone just tell me the name for this kind of circuit? And maybe give me a hint as to what general components will accomplish this?

Thanks so much.

Winston · Accepted Answer

Pulsewidth modulation or PWM.Very popular as speed controllers in drill motorsand many other things, like the Tesla cars.Search phrase "pwm motor controller".--Winston

NT · Answer

Building a pulsed mains psu: I dont know how skilled you are, but few at school could do it. A simpler option is a series capacitor between mains and fan. Take a little care not to get the wrong value of cap.

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NT

josephkk · Answer

Did you notice the on/off times quoted?I had understood that for automobiles they used variable frequency =drives.?-)

Winston · Answer

By jingo, you are right!I should have checked first.  (Blush)--Winston

Tim · Answer

It's OK to ask your teacher -- that's what he's getting paid for.

But at any rate, you should be able to do this fairly easily with a timer circuit and a solid state relay. Use a 555 for the timer, look up the on/ off circuit in a cookbook or on the web, and connect the output to the relay input (make sure that the 555 can drive enough current to make the relay happy). It should work like a charm.

Yes, it'll stress the fan motor. You probably want to have it turn on for more like five seconds, then turn off for a minute -- but you can experiment to see what actually works.

Rich Grise · Answer

To make it really classy, use a MOC3030 series zero-crossing optoisolator.It will minimize switching transients.And I agree, that's what the teacher is there for.Cheers!Rich

George Herold · Answer

ee)gon/Yes or even 'regular' coil activated relay.When the fan motor turns on, from a dead stop, it draws more current.Once it's spinning the current decreases.  More current means moreenergy.. so if this is for some sort of energy conservation idea,you'll want to take that into account.George H.e quoted text -

120v 1.5a pulser?

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