Power supply/speed control

Original post by Martin Perman

"Gentlemen,

I want to put power feed on both my Centec 2A Horizontal milling machine and my mill drill, I intend using an ex wiper motor on both.

Can somebody point me in the direction of drawings so that I can build a mains supplied power supply with a speed control.

Thanks,

Martin P"

Yes please, and if at all possible without strings of initials. Letters and numbers to identify parts to be ordered will of course be useful. Sorry if I'm hijackig your thread Martin.

Edited By JasonB on 26/05/2014 16:10:03

Simple pulse width modulation (PWM) controllers are probably cheaper to buy already built, then just add a 12v power supply.

Bob,

Thanks for that, I have just had a quick look and you can get a 10A unit for £10.00 or less, its not worth the effort of making one, power supplies are cheap enough as well.

Martin P

Hi Martin,
I agree with Bob's comments especially if you are not already into electronics. You will find many PWM speed controllers on Ebay. The first step is to find out how much current the motor draws while driving the table. I would choose a controller with a current rating at least 50% above the motor current. For the power supply you could probably use a battery charger of suitable rating with a capacitor of about 4700 uF 25 volt rating across its output. You could use a switching arrangement similar to Mike Cox's design here. I just use a three position switch for forward - stop - reverse and a push button switch to override the speed control so it runs at full speed when pressed.

Les.

Les,

Thanks for that as well, I had worked out stop, start, fwd and rev as I'm a mechancal engineer with electrical abilities it was just the speed control that without help is slightly out of my reach, but as I often tell apprentices it could only go bang once

Martin P

"it could only go bang once "

As written in engine manual of Japanese origin translated to English, "press button marked start till engine explodes"

I've just been looking at the net, and speed controllers are cheap, but not so the power supply, guess that's down to the transformer, it seems the way to go. Takes the fun out of it tho'.

Gentlemen,

I've just notice my original post has gone,can somebody tell me why and how please, I know that in the title all the letters were there but not necessarily in the right order but couldn't find how to correct it.

Martin P

This is the same thread but I corrected the title. Only Moderators can edit these things.

Though I have just noticed your original post has gone AWOL some time after I corrected the title? Have managed to find the text but had to put it in Gordons post. Best I can do.

J

Edited By JasonB on 26/05/2014 16:04:32

Edited By JasonB on 26/05/2014 16:10:49

I was only curious,

Martin P

Managed to completely confuse me, has no-one any idea where that post went?

I've seen a few examples of duplicate postings over the last couple of weeks, but not disappearing ones.

Neil

Only thing I can think of is that another mod tried to edit the original post in the admin area ( it was reported to ask for the spelling to be corrected in the title) any editing in the admin area can loose the post. I have talked to Katie about this before but don't know if it was sorted.

I acted on the report and altered it via the edit tab at the top of the thread so could not have been that. Then deleted the report as it had been dealt with, the report has gone so it must have been that I deleted and not the opening post. Luckily I had ME open in a few tabs and was able to go back and find Martin's post which I copied and pasted into Gorden's post as thats the only way to keep cronological order.

J

How about the power upply from an old computer? At least regulated and smoothed.

graham.

Hello Martin, I feel guilty now , not that I had anything to do with your post getting lost. I have found a biggish transformer with 24V output, wire is about 1mm thick so should be ok for a few amps. I would like voltage control with meter etc. All the circuits I've found on the web seem over complex, can we still buy a full wave rectifier and variable resisters? Or is it cheaper to buy the integrated circuit stuff? I will buy a completed speed controller, no point in trying to make one.

The transformer that I use for my power supply comes from an old Zerox copier, it's about 6"cube, I found it was an auto transformer, so I wound another layer to give an isolated supply at 18 volts, I used double winding of either 18 or 20 SWG wire (can't remember). Ian S C

Help !

I am looking to fit a power feed to my WM 16 table, I have a 12v wiper motor, a Potentiometer for speed control & a DTDP switch for Fwd -Off- rev but am looking to fit a 240v AC - 12v DC transformer for the supply as I don't have a battery charger (pinched when low life got into my garage) I would prefer to have a 'wall wart type.. simply plug into 13 amp socket connect to DTDP & away it goes..so to speak..am I on the right track & what type of transformer (Wall wart) would be suitable? I am assuming that I could remove the round pin connector from a cheap wall wart & connect to the DTDP... or maybe Maplins have a connector.. if you get my drift

I have looked on e bay & there are hundreds to pick from... confusing.. I looked particularly at ..

**LINK**

is this feasible/suitable considering it says it is a LED driver?

I don't know what amps the motor will draw when connected to the leadscrew as am in the dark as far as electrics / electronics goes., I want to K.I.S.S. in assembly & not looking for 'spaghetti junction' set up. I'm sure that some of you Electronic whizz kids could help.

TIA

George

Hi George,
I do not think you will find a "Wall Wart" type power supply with a large enough current rating to drive a wiper motor. I also think the LED power supply will not give enough current. (By the way your link does not seem to work.) I would guess that the motor will take about 5 amps but you should measure it before ordering any parts. Use a car battery and an ammeter. Just using a potentiometer for speed control will give very poor speed regulation. A PWM speed controller would be much better.

Les.

I believe computer power supplies can provide +12 volts at a lot more than 5 amps (But not at the -12 volt output also provided)

There is a lot of information on the net

Regards
john