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ac is to powerful, need help asap!!!!!!!!!!!1 Answered

i bought a dimmer switch for a 110v motor. i hooked it up and turned it on, it went to fast for what i need it to and it was on the lowest setting. it is a 600w slide dimmer switch. is there any way i could make it slower?



a 555 timer is a really cheap IC, you only need like 1 or 2 capacitors, 2 or 3 resistors and a potentiometer. All in all you could probably make one for 4 or 5 dollars if you buy everything from radioshack. and like 1 dollar if you go online the 555 timer of course can't drive ac directly, so you use a triac (a semiconductor that's a switch, like a transistor, but doesn't have an inbetween value, plus it's meant for ac).

actually I don't know how to use a triac in a situation like this, for a triac to turn off the voltage has to be removed or equalized on each side. Someone with more electronic knowledge, would the brief, split second that the ac voltage is 0 be enough to turn off the triac?

1) a triac is a solide state switch. unless the voltage at the gate went to below the threshold voltage, the triac stays on. 2) unless your idea is to turn on and off the triac rapidly, i really have no clue what your plan is. 3) perhaps a variac, like the ones used on tesla coils and electronics for testing, would be a much better option. they allow power to be applied more gradually. unfortunatly, they are rather expensive.

ohhhh, I think i was getting triacs mixed up a bit with scrs, I was just reading about all of them a few days ago and I guess I got some of the data mixed up.

A Triac is TRIode for Alternating Current and is the equivalent of two silicon-controlled rectifiers (SCRs/thyristors) joined in inverse parallel (paralleled but with the polarity reversed)

didnt i say that?? sorry if it sounds rude, but i could swear i said that, and if i didnt, im having false visions.

Hmmm, I searched for those exact words and didn't find them :p Anyway, yeah, I was clarifying what you said, in the event someone misconstrued what you wrote (you can go back to sleep now LOL). I am curious, why is if offensive if I had repeated what you said? If that would be the case, aren't I then "agreeing" with you ? ;-)

its not offensive; i was just wondering if: my post was deleted my internet bugged i was having early alzimers etc etc

Your internet is bugged, and I can see you through your monitor: and I saw those pink jammies you put on when you went to bed LOL


it works both ways :-P
i can see your night gown. why dancing clowns?

It keeps the bogeyman away; you remember


right ? ;-)

do you mean ET, or from ghost busters?

no. a triac is 2 scrs in reverse paralelle. and an scr is a semiconductor that, when a small current is apllied to one lead, allows a much greater current to flow through the other 2 leads.

. You need to supply a variable frequency to the motor. Your wall dimmer doesn't do that. Search for Variable Frequency Drive (VFD).

Which kind of dimmer. Was it one constructed with a triac internally, or was it a straight potentiometer ? I know a straight pot will cause clipping and vibration in light bulbs when used with an AC supply (we have an old dimmer that makes our chandelier "ring").

I was the first in the history of the forums for the longest time to use the word triac!

..I haven't heard the word till now. xD

not without taking off the cover. if you do but a new one, buy a BRUSHED motor. much easier to vary speed

no screws anywhere? how do you oil it?

I'm not sure if this works, but hook up both terminals of the motor to your multimeter and see if it conducts (or a relativley low omic value). If it doesn't conduct at all you burnt out your motor. I think... that's how I test dc motors, and I think it should be the same for ac.

maybe you tripped a breaker? Plug in a lamp or something to where you plugged it into and see if it lights.

no clue how much $ pop of the back or cover. or look for brush change ports or new brushes in the catalogue. try the manufacturers web site.

find out if the motor is inductive or not, then buy a motor speed controller at a hardware store.

my only other guess would be to simply use a couple of other items to draw power away or maybe use a brake to load it extra, either that or modify the rest to make it work, the belt would stay on if you added a couple of plates to keep it on or a tensioner in the form of a spring loaded wheel, that and you'd have wayyy more power for demonstration that way, I would take no time to charge the vaan de graaf...

there is no backplate you can take off?

maybe use a transformer and make it run on a lower voltage? Might not work though. I wouldn't suggest a weight, if it's for volt de graff can't you use a pulley or gear system so it seems slower?

that would not work on an inductive motor (a true ac motor) kruser, is the motor inductive of brushed? if its brushed, you can easily vary the speed. inductive motors are generally harder to control.

A Triac is TRIode for Alternating Current and is the equivalent of two silicon-controlled rectifiers (SCRs/thyristors) joined in inverse parallel (paralleled but with the polarity reversed) as shown in the schematic symbol below.

A little more info can be found here at the wikipdia link to Triac


If it's short term solution that the electronics are likely to survive for a bit then grab some gears and just gear it down a bit, also if it's for a van de graaf then is the speed that important, also it may go much slower once under load...

well how much slower do you want it?

555 timers are really easy and adjustable with a potentiometer. How many watts or amps does the motor take?

use pwm I'm not sure how to do it for ac though, maybe a simple solution would be to use a 555 timer driving a triac? I've never actually used pwm for motors, but I don't see why a 555 timer wouldn't work. I've also never used a triac before.

it is the old problem that it isn't a good idea to run anything using inductance off of a straight potentiometer.

The reason: a resistor (and a pot is a variable resistor) alter current, not voltage. The task is to generate a variable voltage and frequency power supply from a fixed voltage and frequency power supply (such as a wall-outlet power supply).

If you are going to vary the voltage, and thus the speed you need more electronics, not more resistance.

Here is a straight-forward link to an explanation of three ways to do this.