VS Dimmer Switch Use

[John Moorhead]

Folks -

Okay, question about lekturcity here... Could I use a standard incin.. incandces... encand.... oh hell... light bulb dimmer switch as a variable speed switch for a router. If the router draws less than the switch is rated for, will I run into a problem? I don't care about the switch, I just don't want to damage the router.

I built the router table in FWW from several months ago and I have it set up so I can mount three routers on the beast... unfortunately, none of these are VS, and I will need to cut the speed down so I can use a panel raiser in one of them.... I have a cheap HF plunge router that I set up for the horizontal routing, a Melwilke.... Malwalkie.... Milwaulck... dammit.... Red "body grip" router for table use, and my DeWalt Plunge router for the overhead routing.

My only VS router, the Bosch 1617, is my favorite, so I am saving that for hand-work and I don't want to put that one in the table.

Please let me know if y'all think this'd work, or if I'm asking for trouble. As for not buying a VS router control, or yet another router, I don't need help with that... I already know that I'm cheap!

John Moorhead

[Rob Mitchell]

It would probably not work very well. Incandescant lamps are resistive loads - motors are inductive. So, even if the 'watts' label matched it is not a safe setup.

[Knothead]

I have an old 3HP ryobi (Not soft or electronic start) in my router bench and use a 4 speed ceiling fan switch which to date hasn't started any fires. I do find I only use 2 speeds though medium and high. After 20 minutes of routing dadoes nothing is hot to the touch.

[Andy Dingley]

This is a common enough approach, but it's more useful for drills than for routers. Many routers now use up to 2000W, which is considerably more than a light dimmer can handle. The biggest low-cost light dimmers I know of are about 500W max.

Routers with built-in speed controls usually have soft-start and may have feedback control of speed, both of which are an advantage worth having.

So for a small router, and a big light dimmer, then I _might_ go for it, if it as my only option. But it's not something I'd particularly recommend.

As to the inductive load business, then I wouldn't worry additionally. It won't stop it working, just de-rate the maximum capacity -- and you're already having to worry about that.

[mac davis]

Ok, Andy.. but that leads me to another question: I've heard that some motors, mostly ones in appliances, will be damaged by low power... but I don't know if they're talking voltage, amperage or watts.... Can the router be damaged by the reduction from the dimmer switch?

mac

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[Pat Barber]

I think you would do better with one of these..

and search > Folks -

[Andy Dingley]

How many possible variations of dimmer and router are you concerned about ? 8-(

There's a problem in running any motor at low speeds, in that the heat dumped into the motor for a given torque will rise. If you throttle the motor back, and a high load slows it even further, then you have a risk of overheating.

There's also the waveform issue. Simple dimmers work by phase control. Their output wavefom becomes "spiky", which means there's an added high-frequency component. Electric motor windings don't care for this, and again there's more heating going on.

So you can run a motor with a dimmer, but you need to de-rate it for useful power and to watch the temperature of the windings.

With a drill, the use of a speed control might be for low-power low-speed uses like a polishing mop. It works well enough.

For a router though, such an additional speed control is typically used with an underpowered high-speed router swinging a large speed-limited cutter. This still needs a fair amount of torque and thus power, and the power may already be marginal for a small router. This is less successful.

[Phisherman]

[Andy Dingley]

And how many routers are there that don't use this type of motor ?

[bridger]

[mac davis]

Thanks, Andy... I don't have a need to change speeds, but now I know that I wouldn't try a dimmer switch if I did want to..

What made me ask the question was something that came up recently in an RV forum, about checking the voltage and amperage at RV parks/hookups... Someone said that appliances, especially refrigerators, could be damaged by "power drops" more than power spikes..

mac

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[Andy Dingley]

I don't know much about US practice for fridges in RVs, but the UK practice is to use a different type of fridge mechanism anyway. Although there's a well-known problem with some domestic fridges and under-voltage, this shouldn't affect the RV type.