433Views23Replies

Author Options:

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?

Tags:ineed

Discussions

0
guyfrom7up
guyfrom7up

11 years ago

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).

0
guyfrom7up
guyfrom7up

Reply 11 years ago

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?

0
tech-king
tech-king

Reply 11 years ago

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.

0
guyfrom7up
guyfrom7up

Reply 11 years ago

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.

0
Goodhart
Goodhart

Reply 11 years ago

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)

0
tech-king
tech-king

Reply 11 years ago

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

0
Goodhart
Goodhart

Reply 11 years ago

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 ? ;-)

0
tech-king
tech-king

Reply 11 years ago

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

0
Goodhart
Goodhart

Reply 11 years ago

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

teasing!

0
tech-king
tech-king

Reply 11 years ago

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

0
Goodhart
Goodhart

Reply 11 years ago

It keeps the bogeyman away; you remember

IT

right ? ;-)

0
tech-king
tech-king

Reply 11 years ago

do you mean ET, or from ghost busters?

0
Goodhart
Goodhart

Reply 11 years ago

Stephen King's IT

0
tech-king
tech-king

Reply 11 years ago

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.

0
NachoMahma
NachoMahma

11 years ago

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

0
Goodhart
Goodhart

11 years ago

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").

0
guyfrom7up
guyfrom7up

Reply 11 years ago

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

0
Punkguyta
Punkguyta

Reply 11 years ago

I haven't heard the word for ages.

0
ll.13
ll.13

Reply 11 years ago

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

0
tech-king
tech-king

11 years ago

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

0
tech-king
tech-king

11 years ago

no screws anywhere? how do you oil it?

0
Punkguyta
Punkguyta

Reply 11 years ago

Old fashioned eh?

0
guyfrom7up
guyfrom7up

11 years ago

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.

0
guyfrom7up
guyfrom7up

11 years ago

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

0
tech-king
tech-king

11 years ago

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.

0
tech-king
tech-king

11 years ago

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

0
killerjackalope
killerjackalope

11 years ago

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...

0
tech-king
tech-king

11 years ago

there is no backplate you can take off?

0
guyfrom7up
guyfrom7up

11 years ago

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?

0
tech-king
tech-king

Reply 11 years ago

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.

0
Goodhart
Goodhart

11 years ago

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

triac_circuit_symbol.gif
0
killerjackalope
killerjackalope

11 years ago

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...

0
guyfrom7up
guyfrom7up

11 years ago

well how much slower do you want it?

0
guyfrom7up
guyfrom7up

11 years ago

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

0
guyfrom7up
guyfrom7up

11 years ago

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.

0
Goodhart
Goodhart

11 years ago

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.