Variacs, Router Speed Controls, and Ceiling Fan Dimmers?

johnreid

The Variac should be the Cats meow for your Jensen, the Router speed control is like a Fan Dimmer and I believe that the Lighting dimmers are considered better than the Fan Dimmers.
A 15 Amp Variac is more than you should ever need, mine is only 5 and works great..

Variac best
Lighting dimmer second best
Most Harbor Freight stuff wears out in a short time anyhow, save your Money

Reid

Lookie, guys:

a solid state triac dimmer such as that router control, or any suitably rated lamp dimmer (same thing) are just fine and perfect and cheap and small and harmless to a resistance heater such as the Jensen's,
or any other for that matter.

These transistor lamp dimmers have been handling incandescent lamps for over four decades now.

The lamp filament is the same thing as a Jensen heater only much more delicate.
These dimmers do not damage lamps. Ergo, they cannot damage toaster heaters, even less-so.

this is the fact: no one need go shop for a variac when or if a cheap motor control/lamp dimmer of suitable capacity is at hand.

The variac is better, sure, on several counts,

but it won't work any better so far as controlling or preserving the heating element than a lamp dimmer. They are equals so far as the engine could be concerned.

johnreid

In fact the dimmer that is designed for lamps will work fine, the ones built for Fans and Motors like the Router control will not last as long it is how the dimmers are designed.

So no Dont buy the Router control for that purpose, but a Lamp dimmer which in fact costs less too. However if you already have the Variac, it is far better on many counts but lets not sget into a long dissertation here.

It is all in the way tat the different devices are designed. Buy a dimmer switch that is for dimming Lights and make your controller, NOT a a fan or motor driven device speed reducer.

There is a difference.

Mister Occlusion

What no one can tell me is this: You cannot use a light dimmer for motors (or at least are not supposed to), but can you use a fan speed control (ie: the other type of dimmer) for lights/heaters?

I had been using a plain lamp dimmer for years with my dremel. Well, the dremel probably has half an hour on it all told. I bought a fan speed control for it (and one day I will even put it together). But I want to know if I can use this to control the second boiler on my Jensen 20 without melting something.

Reason why I'm half-buttocked shopping for a variac is that I'll need something with more power handling capability once I upgrade my boilers to the 600-odd watt immersion heaters.

Plus there's the retro geek factor...

(I should photograph my computer testing station that is sitting on my steam bench right now while I run diagnostics on DLT drives... it's junkyard geek

)

johnreid

Lamp dimmers more or less rapidly turn the Light bulb on and off, they can harm a motor over time. The Fan controller will get hot and eventually burn out with the heating element. It might work, for a while. The harm in you using the light dimmer to control the Dremel is going to be to the dremel, some have capacitance in them that helps to a bit in that case.
The Variac is a Transformer, and gives you a full waveform, far superior both for the heater and the Dremel, but more costly too.
Triacs, resistors, Autotransformers are the three basic dimmer switches withe the Autotransformers being the most expensive which is also why some of the higher wattage dimmers cost more.
Bubba probaly would get by with a Lamp dimmer but if he has a Variac that is the route to go. Mark, seems to me to be the type that if he does not already need a Variac, he will in the future.
There is a difference between A motor speed control and the heater element will burn it up, it would be a waste of money that could be spent on Steam Engines.

Mister Occlusion

Thank you, John. That's the answer that no number of megalomart employees nor the web could give me.

So I'll either build a second lamp dimmer, or look for an autotransformer a bit more vigorously.

IndianaRog

Mark...I too learned something from John's explanation.

One additional point on using light dimmers...capacity and price.

600 watt rated light dimmers are available at Walmart for about $4 USD

1000 watt rated light dimmers are available in some home impr. places like Lowes or Aubuchon Hardware online...but expect to pay about $40 USD for that extra wattage.

Not sure why they go up 10X in price for 40% more capacity, but such is life. I incorporated a 1000 W dimmer into my Jensen 51 replica's control panel so I can throttle down one of my 660 watt HotWatt immersion heaters...it works beautifully and fits in same exact space as the cheaper ones...doesn't get warm etc.

Knowing you Mark, I think you ought to spring for the 1000 watt right from the get go...maybe two!!!

Rog

johnreid

The low wattage ones are probably a Triac, very inexpensive to manufacture.

Mister Occlusion

Do you know that I have yet to find anyone who sells anything other than a 600watt dimmer? One of the megaloguys even told me I'd have to go to some place that supplies electrical contractors to find such a thing!

...I suppose I could find one online if I looked hard enough..

But I am feeling lazy, and with the state of my bench I won't be steaming anything for 2 weeks anyway

Reid

I'll add only that there are two basic kinds of small motors in the home:

the AC induction motor, which is brushless and does not so much like chopper voltage controls...

the ceiling fan, however, is one of these induction motors.
Because of its design: they are not heavily loaded, and the desk fan is no different, they can survive on chopped waveform AC power although their electrical efficiency drops a bit and they tend to waste bit of the reduced power as heat, and heat themselves through slippage, a lack of lock-step, of the rotor in the rotating magnetic field.

A heavy-load motor such as for an air conditioner compressor, air compressor, etc, would quickly die if operated at reduced voltage of any kind, but chopped voltage waveforms would kill them even faster.

NOW the other motor type is the AC/DC universal motor: your Dremel, your shop vac and most all of your household vacs are brushed motors which can run just as well on DC voltage as on AC.

They do OK on lamp and motor dimmer controls;
The adjustable speed dremels use just such an internal device as a matter of course.

Variacs are proper for transformer-operated devices:
TVs and such that contain power transformers;
heavy wall warts are transformers too,
the lightweight ones are not. Those are solid state switching supplies, cheapies but alright.
As a general rule, nothing is worse for a transformer than a spiky, or square-waved power input. It heats them up and kills them in time.

So variacs are good for anything that a solid state dimmer could possibly operate,
but vital for transfomer equipement, and kinder to motors of any sort, and if we were to reduce the voltage of an induction motor,
not a good plan in general,
the variac is best, but not always absolutely required (ceiling fans, desk fans, etc).

johnreid

The damage isnt always to the Fan or motor but sometimes to the Dimmer.
That is why they sell dimmers for Fans and dimmer for Lamps. A lamp dimmer installed in a residence, used to control a motor can sometimes build up enough heat to cause a fire. Although not hard wired into your house the Fan dimmer which works on a different principal can heat up also with the load that the heater puts on it, thus potentially causing a fire hazard too, but probably burning out the switch before that happens. Why buy a fan controller just to burn it up.

Bubba

Reid

Yes, those are AC or DC, the resistance wire knows no difference.

However, the resistance needed depends on the interrelation between the load's resistance and the voltage supply and the volts needed to drop.

That large unit -might- be of a correct size.

But trust me: you don't want to use a resistance.
All the power you -don't- put into the engine's heater,
must be transformed to heat by the rheostat. And that can be a lot of heat.

A simple way to use resistance safely: put a 110V lamp in series with the hot lead of the power cord.

Then if you put a 15W lamp (extreme example) into the socket,
only less than 15W can develop in the engine's heater.

If you put a 1,000 W lamp (say) into the socket, the lamp will be glowing at less than full power,
for the heater will be getting more nearly its normal full voltage.

But this sort of plan is not the best by far.
Better to transform a high voltage to a lower pressure, than to try to choke it down with a resistance, in these sorts of applications.

Classic

mc_mc

What would happen if you put two of the cheap lamp dimmers in series? Would one add to the effects of the other, or would the second dimmer make no difference.

Or maybe in parallel they would be able to handle a larger load as it would be split over them?

johnreid

I would be scared to death to use those cool looking resistors, they might work, BUT.

mc, it is wiser to buy a heavier Dimmer instead of trying to use multiples, when it is involving electricity why take chances. I would much rather burn up a heating element than lose a hobbiest. I strongly recommend against doing that

The heavier dimmers are in fact approaching the price of a used Variac.

The actual voltage is reduced with a Variac, and many motors lose efficiency as the voltage is reduced. This is why many use belts and gearing to reduce speed. Some motors perform well with reduced voltage.

mc_mc

Where does the voltage go when the variac is turned down, does it get expended as heat? I know my light dimmers at home get warmer when they are turned down to very dim.

johnreid

The Variac is a transformer and is cool in operation the Dimmer is acting as a resistor and thus gets warm. The Variac is much more efficient, but also more expensive to manufacture.