A question for an electrical engineer...

[Terrence Brennan]

I have an old Agfa Rapiline 66 processor which is giving me some electrical grief. I have found, using the spare parts I got when I bought another Rapiline 66 as a parts mule, that I can bypass the electronics and run the various functions manually.

The problem I need help with is the drive motor. It is a direct current, variable speed motor, which still works, but the speed cannot be varied. Fortunately, it is stuck at the minimum speed, which gives me a 60-second development time. But I fear the controller could fail at any time.

I have done some reading on line, and I believe that I will require a DC motor controller; but which one? I need input on how and what information is required to make the selection. I don't have the info in front of me, but I could provide it to the kindly party who might reply to my cry for help.

Please note that I am not asking anybody to troubleshoot the problem(s) with the processor; I just need to be pointed in the right direction.

 

[mshchem]

This is interesting

https://www.elprocus.com/what-are-the-best-ways-to-control-the-speed-of-dc-motor/

There's a bunch of info on DC motor speed controllers on the web. Not sure if this helps

 

[Mark_S]

Do you know what type of motor you have? (how many wires go to the motor).
Texas Instruments make chips to control many different kinds of motors, and for most of them, they have evaluation boards which are intended to allow engineers to try out a particular chip easily - they are priced very reasonably. As an example, the TI DRV8837C is a 1A motor controller, and you can get the evaluation board which includes a microcomputer controller and all kinds of goodies for about $50.

 

[Deleted member 88956]

Looking quickly at what this Agfa thing is to begin with, there is apparently a reed switch that works within speed control system. If that's the case, all you may need is new reed switch, a cheap part. They will die by own life. At least this should be an easy one to replace and see how things change. Since it's a magnetic switch, magnet itself is possibly a problem too, including alignment of the two (magnet and red switch). I am only guessing here, but that is what I have fond being discussed on this particular machine and I do know reed switches are great, so long as both parts in working chain are in proper condition and aligned correctly, so magnet triggers switch when passing by it.

 

[mpirie]

I recently purchased a PWM motor speed/direction controller to drive the motor on my Jobo CPA2 for about £25.

There are many on the bay of e. Because of the ability of the controller to work over a multitude of voltages, i was able to source an external PSU to drive the motor and avoid the Jobo built-in electrics.

Mike

 

[Tom Kershaw]

I recently purchased a PWM motor speed/direction controller to drive the motor on my Jobo CPA2 for about £25.

There are many on the bay of e. Because of the ability of the controller to work over a multitude of voltages, i was able to source an external PSU to drive the motor and avoid the Jobo built-in electrics.

Mike

I can't remember the exact circumstance without looking at my notes, but when I was running a ATL-2300 I had to wire up an external PSU to run the pump motor as the Jobo supply to the component had failed.

 

[Chan Tran]

If you can read the voltage and current rating on the motor you can buy a new drive that control the speed. But for the processor I would use stepper motor instead of DC motor.
Since your unit is still working I think it's just the potentiometer problem. Should be an easy fix.

 

[beemermark]

You control the speed of a DC motor my controlling the voltage. You can control the voltage by any variable resistor.