Thread: Calling all electrical experts - DC motor conversion

Now to the questions.

1) There is a Hall effect sensor that connects to the PWM. What is this for and should I look to keep it?

2) This is the speed control module. I am keen to remove this and use my potentiometer instead. There are 5 wires to the speed control unit and I would assume 2 are the power for the LEDs and maybe 3 could control the speed. But really I have no idea. Anyone know what's going on here and if I can replace with a pot?

Front panel



Wires into speed control and Hall effect sensor:



Hall effect pickup:



Speed control module:



The pot I'm trying to use:




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The hall effect sensor is probably speed feedback. Might be worth keeping.

Ray

Originally Posted by RayG

The hall effect sensor is probably speed feedback. Might be worth keeping.

Ray

Thought that might be the case. I assume it varies voltage to maintain speed.


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I'll have a go.
Prox switch is speed feed back as mentioned. I think for the digital display only.
I think the speed control is multi speed not variable.
Pressing the up/down buttons increases or decreases a counter that varies the pulse width to a pre determined value that corresponds to the counter value..
Pressing the stop button resets the counter to zero.
Only a guess but if it is correct I don't think you could adapt a pot easily if at all.

Got it NCArcher. Looks like I need to incorporate the button module into my control box then.

I will check where the wiring goes for the hall sensor too. If it goes to the display can I assume it's not of benefit as it doesn't interact with the motor?

Thanks for the advice.

Again, I'm only guessing.
If the prox switch goes straight to the display then I think it's pretty safe to say it will have no effect on speed control.

Yeah I does go straight to the display.


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I've been googling. The motor control board appears to be a generic one. probably made in china. I'm almost certain that you can connect a pot in place of the speed control unit. I'm just not sure yet how to do it. The red and blk wires are probably +5V and 0V supplying the speed control board. The Grn/Wht/Gry wires are the speed control inputs. It may be as simple as placing a 10k pot on these terminals but I can't find any specific info or cct diagrams on these boards.

Interesting. Maybe the pots not completely out yet then. I assume I have no need for power if I replace the board with the pot?

Eg remove the red/black (if they are power for the board) and work out which ones go to which of the 3 connections on the pot.

Is there a way to test resistance across each wire to see which is ground and which is the in/out for the pot wiring when the board is live?

Looking at the back of the board there is a common connection between all the switches (up, down, off). Would that correspond to the ground on the pot?

If so what's the risk of I get the other 2 connections on the pot mixed up?

Hi Neevo,
The biggest problem you will have by far is keeping to motor cool. Have a look here https://www.woodworkforums.com/f65/mars-lathe-dc-motor-conversion-159263
I ended up cooking my motor, i think the braking didn't help but i just could not keep it cool.
Nearnexus may still have some KBIC controllers left if you want an easy hookup solution. They are not that expensive.

Cheers,
Ew

Cheers Ew. I will keep an eye on that. Just run the motor on the bench with no cooling and it didn't even get warm after 2 mins on 20% power. No idea how that will translate in the real world though.

Also tried to wire up the pot but it did nothing. Looks like I might use the board for the moment, plus I get cool lights to see where the motor is at.

I'm no expert, but for a pot to work, the speed control would have to react to either a variable resistance or a variable voltage or a variable current.
The output of the push button controll might be any of these or it might be digital (some sort of numerical count) - in which case a pot is not going to work.
I suggest you firstly put a multimeter across the control lines and if that doesn;t tell you anything find someone with an oscilloscope to have a look at what the output is doing. That would clear it up I think.
Good luck and let us know what you find out!

This is probably getting a little beyond my abilities. Plus the original board works a treat and has speed indicator leds.

I think I will rework/make my control box and include the board as the speed control instead.

Cheers all.

Ew I will let you know how the temp goes on the motor. I need to make a fan for it as the one I have is the wrong way round as I need to reverse the motor.