Hi all,
I have two treadmill motors with controllers. They are old, from the 90's. They have scr control boards and work very nicely with their upper control boards. These boards are small and I would like to use them as controllers for my machinery (drill press and sander). My problem is that I don't understand what is going on in the control circuit. The cable has a pinout label and has three pins of interest, one is photoeye coming from a reflective rpm counter, one labeled zero cross, and a third labeled scr control. When the motor is running I put an oscilloscope lead on each of these points and this is the result.
Above is the photoeye at minimum speed.
This is the photoeye at about half speed.
this is the zero cross pin (this does not change with speed of course)
This is the scr control pin. I would expect this to change with an increase in speed but it does not.
So what my question is, what is the lower board expecting? I was planning to replace the upper board with an arduino nano but cannot write the program if I do not know what the output needs to be. I was expecting that the lower board would need a zero crossing based pulse to the triac that would change with duty cycle but this does not seem to be the case. Is the photoeye contributing to the speed control perhaps?
I currently have a partial schematic of the lower board but it is not complete yet.
Any ideas what might be going on would be helpful.
I have two treadmill motors with controllers. They are old, from the 90's. They have scr control boards and work very nicely with their upper control boards. These boards are small and I would like to use them as controllers for my machinery (drill press and sander). My problem is that I don't understand what is going on in the control circuit. The cable has a pinout label and has three pins of interest, one is photoeye coming from a reflective rpm counter, one labeled zero cross, and a third labeled scr control. When the motor is running I put an oscilloscope lead on each of these points and this is the result.
Above is the photoeye at minimum speed.
This is the photoeye at about half speed.
this is the zero cross pin (this does not change with speed of course)
This is the scr control pin. I would expect this to change with an increase in speed but it does not.
So what my question is, what is the lower board expecting? I was planning to replace the upper board with an arduino nano but cannot write the program if I do not know what the output needs to be. I was expecting that the lower board would need a zero crossing based pulse to the triac that would change with duty cycle but this does not seem to be the case. Is the photoeye contributing to the speed control perhaps?
I currently have a partial schematic of the lower board but it is not complete yet.
Any ideas what might be going on would be helpful.