12 volt motor speed controller

I'm helping a friend to power his mill table and I'll be doing the wiring. he has a small window up/down motor, and bought a 12v-40v 10a pwm dc motor speed controller dimmer voltage from ebay. He would like a fast return push button as fitted to Bridgeport mills. Can any one inform me where I should fit/ solder wires for the fast return push button, or is it actually possible on these tiny controller boards where all the components are cramped up together. John

Can you provide some information on the board ? As a TOTALLY WILD GUESS there is probably a power mosfet that does the switching of the motor current. Using a switch to short source and drain should work. (The switch will have to carry the full motor current.)

Les.

I take it you mean one of these John?

The speed control is on the centre pin of the pot marked 100k with the control knob. There are three connectors soldered to the board. One side will be ground, the other at supply (+5 or 12V), and the centre pin connects to a wiper varying between 0 and supply as the know turns.

This version of the PSU would be easier to work with because the pot is detached and can be 'got at'. The wiper is on the White wire.

In principle, fast can be achieved by wiring a switch between supply and the wiper. Unfortunately not as easy as that. For example, if the wiper is turned to 0V, connecting supply to it will cause magic smoke. When the button is pressed, it needs to disconnect the pot before applying volts. The other complication is the need for a reverse switch : the controller is unidirectional, so it's output has to be switched too.

Getting complicated: the control circuit has to flip the motor direction, then disconnect the pot, then apply the go fast voltage. And because it's bad for the electronics to from zero to hero in microseconds, it would pay to accelerate gently up to speed by charging a capacitor through a resistor.

Certainly can be done, but not by soldering a few wires. I'd be inclined to keep it simple with a reversing switch and manually turning the knob.

Dave

If it’s the type as Dave has shown, you could possibly unsolder the potentiometer from the board and fit it remotely. Get another pot of the same value and connect the 2 ends in parallel with the original pot and wire a changeover switch between the wipers of the 2 pots and the circuit board. One pot used to set normal speed and other pot to set fast speed. The switch used to select between normal and fast.

You will still need a change over switch on the output for forward/reverse.

The controller might not like changing from forward to reverse though without stopping the motor first as Dave says.

I bought a similar controller but one controlled by a signal from an Arduino. I managed to destroy it while experimenting with a small geared dc motor, so yours may suffer the same fate! I think the current rating is a bit optimistic.

I have since bought a different controller for use on a battery loco to control 2 x 12v 150w motors. I have tried it on the bench and on load. So far it’s seems ok.

A controller like this might be better for your application. It has remote pot and a reversing switch already fitted.

60A PWM Brushed DC Motor Speed Controller CW CCW Reversible Switches 12V/24V/48V.

These are available from many sellers.

Stuart

Edited By Stuart Smith 5 on 19/07/2021 13:42:24

I very roughly followed this video:

**LINK**

Full speed can be achieved by completely bypassing the controller, but (depending on the power supply) may over-drive the motor. I am applying 19 volts to my 12V wiper motor at full speed. I thought that was enough! I might yet change it for a 24V wiper motor, but all the bits I needed (apart from the speed controller) were easily to hand.

The video offers the alternative wiring dodge for the speed controller I purchased for about £12.

I chose to use a wiper motor, after looking at the physical sizes of the two options (wiper or winder motor).

edited to say sorry for the adverts before the video starts.🙂

Edited By not done it yet on 19/07/2021 13:40:15

I built a power drive for my mill table. This allows slow variable speed for cutting and full speed for the return. The cut direction is selectable. The speed control is based on a pulse width modulated speed controller. Full details are here:

http://mikesworkshop.weebly.com/mill-power-feed.html

Mike

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That’s very tidy, Mike … thanks for the link

MichaelG.

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Given the demise of Maplin : May I ask if this is the relevant module ?

https://www.rapidonline.com/mfa-919d2-series-pwm-voltage-speed-regulator-modules-82349

Edited By Michael Gilligan on 19/07/2021 17:27:56

Back again, many thanks to all who responded to my request regarding the 12 volt motor. controller. Unfortunately my friend had already bought the bits including the transformer. I think can persuade him to put his bits to one side and buy a package some thing like Dave and Stuart suggest. I made my own way back in Sept. 1990 following an article in ME, all the electronic components came from a discarded washing machine control board from the tip, when it really was recycling. Thank you Mike for pointing out Mikes workshop Youtube very good and ingenious.

Hi John, Guys,

When I built my window screen wiper motor driven mill table drive, I used a variable voltage lab type power supply. Mine supplies 30 volts at 3 amps. I just use the whole 30 volts for fast traverse and around 7 volts for actual milling.

My direction control is via a tumbler gear very similar to the one found on a Myford lathe, giving me forward/stop/ and reverse directions.

This is a picture of mine mounted on the left hand side of the table. I just pull the white knob out and lift or lower the lever to select the direction or neutral. It also has the advantage that I can still use the handwheel at the other end when neutral is selected.

All the gears were salvaged from printers. photocopiers and the like. The motor unit is a "Trico" one salvaged from the local scrapyard.

Michael - the speed control module I used MFAcomodrills part number 919D29, see:

https://www.mfacomodrills.com/pdfs/Speed%20regulators.pdf

Regards

Mike

Thanks for that, Mike

MichaelG.