[gridevolver]

I'm a teacher at secondary school who has found a little used CNC lathe in a stock room, it's an 1984 conect 121 that used to run on a BBC. I've been in contact with CNC4you who will be able to supply and talk me through setting up the stepper motors. They can't help me with the spindle motor control. I have been inside the old control box that was connected to the BBC and found a Neco DC motor control PCB. It's 240Vac in and 180V DC out how ever I have little/no idea how to use this card. Any help would be excellent. Please see attached pic.....

Attachment 183012
Attachment 183014

[Al_The_Man]

It appears to be a simple SCR type controller for a DC brushed motor, do you still have the motor? otherwise one of the TreadMill motors sold on ebay should work.
The power and armature connection is shown, the only others are T10,11,12 which would either have a 5k/10k pot connected across it or as it shows being used in the picture with just 11 & 12 which is a analogue 0-10vdc input, if using Mach or similar controller, you can obtain a BOB which converts the PWM signal from Mach to an analogue signal for T11/12.
The white black T8 could be an enable?
Al.

[gridevolver]

Okay, I would say I understand 10% of that.... What would I need to do in order to run the DC motor (which I do still have on the lathe). I would just like to have a nob (pot) on the front of the lathe enabling me to dial in the motor speed... are you saying that i have to put a POT across blue and grey? or a voltage across blue grey? I will be running mach3 but will not be looking for it to control spindle speed to start with!

Cheers, Ethan

[Al_The_Man]

Having the original motor is an advantage, I assume the controller is still hooked up to the machine? so it looks as though all you need to do is remove the two conductors at 11 & 12 and tape them up, I would assume they currently go back to whatever controller was originally used.
So you would need a 5k or 10k Linear Potentiometer, the outer ends of which would be connected across 10 & 12 and the slider would go to 11.
Mount the pot on the panel with a suitable knob and Voila (hopefully).
By doing this you cannot harm anything, the only thing not quite apparent is the T8, I would try the pot first and see if anything has to be done with T8 after.
There would normally be a way of powering up the drive, either by a power relay on the AC side or could be the enable such as T8?
I think I read INH on T8, if so this would be Inhibit.
Al.

[gridevolver]

That's much more my level!! I'll try a slider or there tomorrow and let you know how I get on!

Many thanks for your help!

[TAREQ]

Hello

Did you find a solution for your speed controller?