ELECTRIC MOTOR ...HELP PLEASE

Yep thats what I was going to do but I need to know if I can attach a variable speed device that will allow me to turn a knob and get constant speed rather than holding the trigger on......

SARGE

yes the right rated potentiometer should do the trick

Thanks Glenn....is it hard to butcher a drill motor and wire in a VSD. Will it effect the motor can I run it on reasonably low revs without burning it out?

SARGE

FS, you can just plug the motor into a VSD and control it by varying the 240V input (or whatever voltage you're using.

FS,
Variable Speed Drives are common in the electrical industry, with no ill effects on the motor you are contolling. I once used my little unit on a drill to turn a spit pole around at very low speed for hours, no probs.

Glenn you are WA so am I where did you get your unit from? Tried the usual suspects dick smith jaycar etc no luck.

SARGE

Almost right Glen.

Heat kills motors. On an ordinary AC motor, if the motor is going slow then the cooling fan is also going slow.

Properly designed systems have a separately wired fan on the end of the motor that runs full speed even when the main drive motor has been slowed down.

Glen was right about the VSD devices. Not much in them, thyristor, resistor speed control pot and a capacitor. But, as mentioned above, if you slow the motor down it looses it's cooling.

How much load will you have on the motor ?

Hi Kiwi......not much load at all same as would be excerted if drilling through a piece of pine but it will be under load for around 15 - 20 min at a time. I was actually told a dimmer switch wired in line would do the same thing any ideas on that ?

SARGE

Yep, that would work but check the wattage of the dimmer first. Some dimmers are not rated very high (watts). Also, be careful how you wire it up, dimmer will probably be in the black return wire of the circuit and not the switched red feed wire.

Hi Kiwi, You are right.... the old black and decker got really hot (smoke from motor and meat), but at the time we weren't too concerned as long as it kept turning the lamb. The insulation on the motor windings must have been pretty good eh!(dont make them like they used to).
and ....FS... I made my unit as a tech school project, and still works 20 yrs later.

Try the light dimmer if you've got one in the spares box, but also check out a fan motor speed control (you know, those ceiling fans) which use a zero-crossing commutation of the AC. These work on motors better than the standard lamp dimmers and will prob take the start current of the motor better as well. Will probably be labelled as a "fan and lamp" control. More expensive tho.
There used to be lots of kits for 240v universal motor speed controllers, but they seem to have dropped off the market these days, prob coz of safety liability issues. Oatley Electronics have a few low voltage controllers, but not what you want. Otherwise there are plenty of published circuits for speed controllers which can be made quite cheaply.
Gerry

Actually, I think it is 7.2V.

So why the mystery? What is it for?

Winch for a peddle car ?