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fan speed controller


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hey, I've got my eye on an electric forge blower, but the speed controller is missing, can anyone tell me where i can get a speed controller from or what the proper name for them is, and how much it's likely to cost...

Or is it better to just put a valve in the air way and have an on/off switch?

thanks all

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I use a dimmer style switch for ceiling fans on mine - works like a charm - I've burnt a few standard dimmers out before I decided to switch.. maybe they'll work for you, too. First though I'd check to make sure the draw of the fan is within tolerance of the switch.

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Grainger here in the US sales a Speed Controls for Universal type AC/DC motors ...says use only with universal brush-type motors cost is $40 -$50

JimBob makes very good points:
- An online site sells motor speed controls:
... AC speed controls http://www.grainger.com/Grainger/wwg/guideBrowse.shtml
... DC speed controls http://www.grainger.com/Grainger/wwg/guideBrowse.shtml
- These controls are designated for use with only "universal motors".

Be careful when working with electricity:
- any electrical part used that is less than the amperage of the motor/fuse combination can cause an electrical failure resulting in serious harm to your or your family and/or a fire.
- the wrong type of controller/motor or fan rheostat/motor combination could seriously damage an expensive motor.

Disclaimer: I am not an electrician and do not claim any expertise in wiring, electricity or motors. Use my opinions and dumb ideas at your own risk. ;)
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unicorn, yeah I know I'd check with the guys at a really good electrics shop before I linked it all up don't worry :) I wired in my work shop my self including all the welder power lines and trip switches, in fact it's almost imposable to get any electric shock or fire from a modern uk electric supply anyway.
thanks for the advice

jimbob, anvils. co.uk and glendaleforge uk both make blowers with brush motors still :)

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While an SCR-type light-dimmer or a rheostat might work fine & dandy on a "universal" motor, they don't do so good with an "induction" (aka "squirrel cage") motor. With an induction motor, there will be a fairly big range where the motor just sits there and gets hot. It is not good for motors to just sit there and get hot.

Speed controllers for induction motors are quite complicated, and therefore expensive.

Note also: some motors are "self-cooled" and must be run at full speed to avoid over-heating.

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I have an electric fan on my forge . It is a brush type motor from an old hand drier (the type found in toilets to dry your hands after washing them). Electric brush motors can be speed controlled with a simple speed controller that I made up in kit form from Tandys or Dick Smiths ( electronic shops) for around $30. Gives a good variable range of speeds from a slight trickle to a full blast which holds a ping pong ball hovering over the tuyere. I can't fault it and I picked it up in a scrap yard for free. It came complete with the squirrel cage as well.

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I tried using a sliding air valve with my blower running full speed but I only succeeded in choking off the air flow till it was just a small but really forceful jet of air. Slowing down the blower using a dimmer switch was much, much better. It's worth noting that Universal brush type motors are a combination of AC and DC motor designs and they are intended to maintain their torque throughout the speed range. Most power drills, saws, etc fall into this group. A simple squirrel cage blower motor like those used on residential furnaces, exhaust fans, and the like will have lower torque at lower speeds but spinning the fan isn't hard on it and you won't need as much current. Lower current draw means you can use the el-cheapo dimmer switches sold at hardware stores.

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