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Where to get variable electric power controller?
MikeR - 15/12/10 at 06:42 PM

I want to half the speed of my electric pillar drill. My dad has this snazzy little unit that is donkeys years old that plugs between the wall and the drill, he can turn the dial on and it does some magic and adjusts the drill speed.

The drill is an Aldi special, 500w, currently spinning at 280 rpm. I want about 140rpm, but having something that is variable would be nice.

There is something on eblag that seems to do it for 20 quid, eBay Item

So ........ where can i get one locost fashion & no, stealing my dads isn't an option.

jonrotheray - 15/12/10 at 07:23 PM

I also built one years ago from a design in an electronics mag.
I haven't got the mag anymore, but might be able to post photos of the circuit...
...but not tonight, Josephine!

Maybe tomorrow.

Or you could just take your Dad's apart and reverse engineer it!

MikeRJ - 15/12/10 at 07:26 PM

You can control the speed of a universal electric motor using Phase control, probably what the unit you linked to does. However, another source of a phase controller is a common dimmer switch. Provided you can find one rated high enough for your drill you should be able to use it, but you may need to fit a snubber across the Triac within the dimmer since driving inductive loads can cause them to misbehave.

Better would be to look out for an old Variac transformer on eBay (preferably local as they are heavy!)

rf900rush - 15/12/10 at 07:36 PM

If it is an induction motor it will not very difficult to reduce is speed.
The speed (-slip) is a funtion of the mains frequency.
2 pole motors run at 2800rpm and 4 pole at 1400rpm.

That why most pillar drills have the multi step pully system.

Reducing the volts to the motor will slow it buy allowing more slip but to much will not be good for the motor.

If it is a brushed motor like most mains hand drills then a lamp dimmer type swich may work on a small motor.

britishtrident - 15/12/10 at 07:52 PM

http://www.quasarelectronics.com/motor-controllers-drivers.htm

RazMan - 15/12/10 at 10:24 PM

Locost option - How about finding a knackered hand drill with a speed controller built in and rob that?

MikeRJ - 15/12/10 at 11:34 PM

quote:
Originally posted by RazMan
Locost option - How about finding a knackered hand drill with a speed controller built in and rob that?


Because the method of controlling the speed of a 12v DC motor is very different to controlling a 240v AC one!

RazMan - 15/12/10 at 11:40 PM

12Volts?? I mean a 240V electric hand drill ala Bosch or B&D

MikeRJ - 16/12/10 at 03:33 PM

quote:
Originally posted by RazMan
12Volts?? I mean a 240V electric hand drill ala Bosch or B&D


Sorry, for some reason I read "hand drill" as "cordless drill". You are right, this would be a simple way forward if you can find a scrap mains drill.

NS Dev - 16/12/10 at 07:31 PM

get an inverter off ebay, used ones shouldn't be too much

here's one:

Telemecanique Altivar 11 Inverter ATV11HU05M2E on eBay (end time 06-Jan-11 19:53:32 GMT)

that would do the trick

and here's another that might go cheap

OMRON SYSDRIVE 3G3JV FREQUENCY INVERTER on eBay (end time 20-Dec-10 16:26:28 GMT)

sadly I gave two omron inverters away not long ago!!