Motor speed control.

[Jerry]

I've been using a 3KW variac, a 2.5 hp 130 volt dc tredmill motor and a digital lazer tack for alt testing.

Sometimes I need to move the test stuff around in my shop but its big, bulky, heavy and a pain in the %^&* to move around.

So I thought I'd make a smaller lightweight unit for some of the smaller alt projects.

Harbor Freight has a router speed control (15 amps) but I missed the sale $12.95  now there back at $29.95. I did want to try this speed control but I didn't want to pay twice the sale price either.

So I went to Lowes. They have a 600 watt light dimmer for $4.83. So I thought well what the %^*# I'll try it.

The instruction said use with incondecent light bulbs only. Not motor or transformers or I guess anything inductive?

Well I use a fullwave bridge rectifier with the dc tredmill motor so I thought might isolate the dimmer from the motor.

It works great. I'm using a smaller 1.75 hp 100 volt tredmill motor on this setup.

I can very the voltage down to 13 v and up to 109 volts. Its strange just spinning the motor under no load the ac amperage going into the dimmer stays around 2 amps no matter what the voltage at the motor. Bogging the motor down the amperage will clim prety fast. This is a 22 amp rated motor.

I realized I would be puttting a higher than rated load on the dimmer so I took it out of it housing and mounted with heatsink compound to an old car amp heatsink to help it handel the added load and heat. I guess we'll see how it holds up.

Seems to work good though and the hole thing was prety cheap.

                   JK TAS Jerry

[BT Humble]

That's also a cheap way to get a temperature-controlled soldering iron! ;-)

BTH

[Jerry]

Hey thanks BT. never thought of that. I did think of a small electric heater. I guess anything that has a filiment or eliment will work if its not to heavy of a load?

I've got a small cheap drill press at my store. I'm going to put a small tredmill motor on it. With this speed control I won't have to change the belt around any more. I'll use my lazer tach to read rpm. I'll be able to go way slowewr or way faster or anywhere in between.

                        JK TAS Jerry

[drdongle]

Jerry I am building a test stand similar to yours (right down to the same treadmill motor) and tried one of those router controls and it didn't work, the motor would only turn in pulses not continuously. I opened up the unit and added a filter cap to the out put ( 200 V, 470 uF, I also removed the full power connection which puts line AC to the output), that didn't help, I tried it on a second motor and had the same problem. So I was going to build a 555 based PWM control to drive it through an N channel power fet. but now I'll buy a light dimmer instead

[Jerry]

Hi Dr. D

I'm using a fullwave bridge diode between the dimmer output and the motor. Itryed a 73,000 UF 150 volt cap accross the motor but this caused the dimmer to draw twice the amperage? And the circut didn't work any better?

I'm going to try the dimmer on the pulse charger setup as well. This circut was posted when all the pulse charger stuff was going on.

I'm realy amazed that one littel triac or what ever it is in the dimmer can handel all that power?

                           JK TAS Jerry

                       

[BT Humble]

I've got a small cheap drill press at my store. I'm going to put a small tredmill motor on it. With this speed control I won't have to change the belt around any more. I'll use my lazer tach to read rpm. I'll be able to go way slowewr or way faster or anywhere in between.

Just don't put too much of a load on it when you're running "way slow"! ;-)

BTH

[drdongle]

 Most of those generic light dimmers are only 600 watts so I would be careful about overloading it, there are higher power units available but I don't know what they cost.

 I plan to us a half wave out put rather than a bridge, I don't need to run any of my generators or alternators any where near the 5100 RPM this motor will do, in fact anything over 500 RPM will most likely be overkill. I'm using two 3" pulleys so as to keep it simple, I found out that the shaft on my motor is 11/16 so I have to turn in down a bit to use a 5/8 shaft pulley. I also got one of those hand held Laser tach's ( $50). I will post some pictures when I get it finished.

[Jerry]

Hi Dr D.

My larger tredmill/variac test set works quite well. That motor is bigger and is rated 3000 rpm.

I'll be using a 3" pully on this small motor with a 6" pully on the test generater.

And the gennys will be smaller on this for a lighter load on the small tredmill motor.

                           JK TAS Jerry

[ibedonc]

Jerry I have the same lathre/mill you have and plan on putting treadmill motors in place of the a/c , but I am going to use a board I made , this board will take 12v and boost it to 330v if needed , it ran one of my motors up to 130vdc

[Jerry]

Thats awsom. Will you have a tach? Be nice to know rpm at the work end.

                     JK TAS Jerry

[ibedonc]

I have a circuit for one , will probably use it

[nothing to lose]

You guys are great and a real inspiration, thanks.

 I have a couple DC motors now and wanting to use them as motors soon too. Maybe something like this will help me as I need a speed control too.

[wooferhound]

That would be a cool motor speed control for winding coils.