Dremal tool speed control

I was at the bird shop to get my birds nails trimmed. The lady had a Dremal tool plugged into a sewing machine restate (sp?). It let he control the speed without having to adjust the speed control switch on the tool. Would this in any way be damaging to the tool? I have a single speed tool that I was thinking of doing this with. Seemed like a good idea.

Reply to
Cuezilla
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It doesn't hurt anything. Dremel sells a speed controller to do exactly this. It rectifies the waveform and chops it to make pseudo-DC of varying magnitude. So you can run your motor anywhere from 0 to half its speed on AC.

Grant

Cuezilla wrote:

Reply to
Grant Erwin

^^^^^^ rheostat

Best regards, Spehro Pefhany

Reply to
Spehro Pefhany

"Grant Erwin" wrote: It doesn't hurt anything. Dremel sells a speed controller to do exactly this(clip) ^^^^^^^^^^^^ Well, not exactly. The speed controls used on AC /DC tools like drills, routers, and the Dremel, cut down the width of the on-time of each half-wave. This lowers the speed but does not lower the torque much. A rheostat lowers the voltage, so as the speed goes down, so does the torque. This probably does not matter if you're only filing the toenails of a bird, but if you were using your Dremel for grinding or carving, you would find the speed variation under load to be very annoying.

What makes a rheostat especially bad is that as you increase the load you increase the current draw, which increases the voltage drop, further lowering the speed and torque.

Reply to
Leo Lichtman

A variac works very nicely if you happen to have one. It lowers the voltage without increasing the source impedance.

Best regards, Spehro Pefhany

Reply to
Spehro Pefhany

If I'm not mistaken Dremel only recommends that their speed control attachment be used with single speed Dremels not the variable speed models. I don't know if that makes any difference in performance and torque rating though.

Jimbo

Reply to
Jimbo

Harbor Fright (sic) has a nifty little router speed control for $10 Says it will work with any ac/dc brushed motor to 15A Item # 43584-3VGA I've used it for my roto-zip, grinder and hand drill with good results.

Wali

Reply to
wialgmes

Reply to
Grant Erwin

*You* didn't say "rheostat", but the original poster did (sort of, the spelling was somewhat strange), and you said "do exactly this", so it looked as though you were suggesting that Dremel offered a rheostat, even though you weren't.

Enjoy, DoN.

Reply to
DoN. Nichols

OK, now that rheostats are out of the way... I had cause to look carefully at the speed controller of a Dremmel when mine stopped working. The speed controller is a simple variable resistor-diac-triac circuit AKA a light dimmer!

In other words, get a light dimmer that will handle the current, one sized at

150 watts will do, and that should do the job. The universal motor on a Dremmel is quite an inductive load and triacs like that sort of load, so you shouldn't have any problems with it.

HTH

Mark Rand RTFM

Reply to
Mark Rand

Mark Rand wrote: (clip)In other words, get a light dimmer that will handle the current, one sized at 150 watts will do, and that should do the job. The universal motor on a Dremmel is quite an inductive load and triacs like that sort of load, so you shouldn't have any problems with it. ^^^^^^^^^^^^^ That's odd. Every light dimmer I have ever looked at carries a warning that it is not to be used with inductive loads. On the other hand, I have ignored that warning, and have not had problems. I once used a light dimmer to control the speed of a vacuum cleaner motor I was using as a forge blower, and it worked perfectly.

I guess the answer is to size the dimmer large enough to stand the punishment. What do you think?

Reply to
Leo Lichtman

Does it have the feedback detection mechanism that tells the controller that it isn't running at the speed that the dial position indicates? Engineman1

Reply to
Engineman1

The motor in a Dremel is a universal motor and, as such, has no problems at all with the usage of a reostat or variable resistor in series with the motor. I'll note that there are models of the Dremel that have a built in electronic speed control and you can use that in series with the reostat to limit the max. speed of the Dremel. The electronic speed control works by the phase control of the power so it will do its thing while the reostat will do voltage reduction. There may be a minor loss of control (motor stops) if the input voltage gets too low for the electronics in the tool.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!

Reply to
Bob May

I bought the router speed control from

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$24 including shipping. In a previous thread, someone said this device worked better than the one from HF.

I tried it on a Singer 401 sewing machine. Huge improvement over rheostat control! No "hand starting" even at very low speed. Making a footpedal control for it is now on my project list.

Reply to
Don Foreman

Just what I do. Works just fine. By the way, the cheapest rheostat for the purpose I have found is a sewing machine rheostat. Even new, their about $10. I've bought them for a buck at junk shops.

Boris

Reply to
Boris Beizer

Nope, lights don't really need it either because their load doesn't vary. And it adds to the cost of the circuit, which really scares the manufacturers.

Doug

Reply to
DougVL

Only by sensing current, not via a chopper wheel or mag input.

Most SCR or Triac or Quadrac type controllers are like this to most extents. Remember the line to the motor is inductive as well. Be sure the unit is rated for inductive loading - so the inverse kick of the motor doesn't zap it.

Might not be on the label - so be prepared. Always best not to force stop as the electric field in the windings has to go somewhere. Normally into the Semiconductors - but if it coasts down or stops by itself it is best - lest there is protective circuits - e.g. buy a power plug strip that has lightening strike protection - and use it between the speed controller and the motor. That will protect both motor and speed controller to a great extent.

Martin

Reply to
Eastburn

Thing I don't like about those superstrip overvoltage protectors is that yes, they work - once. After that, you don't have any more protection. And you have no way of knowing!

So a prudent guy would be soldering in new whatever-they-ares, look like Chiclets with leads on them, every few months. And who's going to do that?

Grant Erw- e.g. buy a power plug strip that has lightening

Reply to
Grant Erwin

If it hasn't occured to you Don, consider changing the speed control's pot to a linear or "plunger" pot, which will make the foot pedal design a no brainer.

You could put a little DPDT switch and a three pin socket on the present controller and plug in the foot pedal pot when you need to trade off tasks with SWMBO...(Or is it you who does the sewing too?)

Jeff

Reply to
Jeff Wisnia

actually, they work multiple times, it is just the catastrophic surge that snuffs them. momentary 6-1200 volts spikes are not destructive.

right, nobody. there must be a way to test, some newer units have an led condition indicator. older models sometimes had a window over the MOV. i guess it looks "zapped" when it is. --Loren

Reply to
Loren Coe

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