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Posted:
Wed Jul 07, 2004 5:26 pmby Shawn
After knowing I was going to need a speed controller for my Bosch electric grinder, Maxrace steered me in the right direction.But as usual, I don't have enough patience to wait for one that I order, and, not that i'm cheap, well ok i am, but a trip to the local home depot put enough parts in my hand to build what i needed for about $14 bucks.It consists of a fan speed controller, a regular outlet, and a power cord all installed in a plastic electrical box with standard faceplate.With the box, it can be mounted to a bench or just left alone and moved anywhere you need it.I ran it off and on for about 6 hours yesterday and didn't have a lick of problems. The fan controller i got was a 5 amp one. The motor i have on my grinder is 4.6 amps, so it seems to work ok. They also had larger amp controllers there, but i thought i would try this one first.
Shawn
Posted:
Wed Jul 07, 2004 5:28 pmby Shawn
pic 2
Posted:
Wed Jul 07, 2004 8:51 pmby maxracesoftware
Shawn , it looks like a good Idea
how's the grinder torque at lower RPMs ??
pretty stable and constant ?
Posted:
Mon Jul 12, 2004 1:24 pmby Shawn
Torque seems to be down just a little at slower speeds, but not enough that effected what i was doing. I haven't had to remove a bunch of metal with it yet, so I'll let you know what happens then.With some blending and cartridge rolls, it works really well. I spent all day sat. on a set with it on cast iron and it ran really well.
Shawn
Posted:
Thu Jul 14, 2005 2:32 pmby zc1.8crx
hello
thats what i need, I would like to build one for my self can you tell how its wired. Pics would be nice also if you can thanks. 
Posted:
Thu Jul 14, 2005 7:13 pmby 84-1074663779
Just be aware that an electronic controller like that will only work with motors that use brushes. It most definitely will not work with a (brush-less) induction motor. Most portable power tools and vacuum motors are o/k. Your bench grinder or drill press will definitely not be happy !
The reason being that an ac/dc brush type motor will run slower if you reduce the operating voltage.
However, an induction motor relies on a rotating magnetic field that rotates at 60Hz. The motor running speed is more or less fixed by the 60Hz. Reducing the voltage only causes the motor to stop working properly below normal voltage, so speed control will not be smooth, or in any way really be controllable.
These electronic regulators can also be blown up fairly readily. A more bullet proof way is to use a variac to control motor voltage. The only real problem with using a variac is it's size and weight. Variacs with 20 amp or more ratings are common on e-bay.
While the electronic controllers are small, modern, and neat, after you have blown a few of these up, try a variac instead.
Posted:
Thu Jul 14, 2005 7:20 pmby zc1.8crx
thanks for the info ill search on ebay to find one
Posted:
Fri Jul 15, 2005 12:31 amby larrycavan
Shawn,
I like the way you think! As was pointed out, you may burn it down eventually but you've definitely come up with a good idea and for under 15$. Nice work.
Larry
Posted:
Fri Jul 15, 2005 7:14 pmby 84-1074663779
Motor speed control can be very handy sometimes, particularly for slowing a large electric drill when honing cylinders. If the thing turns slow enough, it is a lot easier to control the cross hatch angle.
Posted:
Fri Jul 15, 2005 8:19 pmby Fkned
I made the same thing(I'm just a little tighter w/my cash,I didn't put a cover on it)about 3 yrs ago and have had no problems at all w/my Millwaukee grinder and it's an 11 amp motor I believe.