3-way PWM Splitter

[philso]

Avoid mixing makes AND models of motor controllers. Most of the ones I have looked at use a photocoupler as the input device. The different models, even if they came from the same manufacturer are likely to use different photocouplers. Different photocouplers will likely have different Forward Voltages, VF. If you put different controllers, with different VF's, only the one with the lowest VF will work.

[nandeeka]

Is this even legal given R53?

R53 Each power regulating device may control electrical loads per Table 4-4. Unless otherwise noted, each power regulating device shall control one and only one electrical load.

[rich2202]

R53 applies to the Motor Controller, not the PWM signal that controls the Motor Controller.

If you are running out of PWM ports, you might want to consider CANbus to control the motor controllers.

[Al Skierkiewicz]

philso,
None of the controllers that I have looked at have a raw opto-coupler input connected to the PWM port. There should be a series current limiting resistor so the V forward difference should not show up as a problem. That being said, single point of failure is likely to raise it's ugly head if one is not careful. A bad controller will take down all three, a pinched wire will take down all three. Your mileage will vary.

[philso]

Originally Posted by Al Skierkiewicz

philso,
None of the controllers that I have looked at have a raw opto-coupler input connected to the PWM port. There should be a series current limiting resistor so the V forward difference should not show up as a problem. That being said, single point of failure is likely to raise it's ugly head if one is not careful. A bad controller will take down all three, a pinched wire will take down all three. Your mileage will vary.

We confirmed with the manufacturer that we should not have been paralleling the inputs of the two types of motor controllers we had and that the LED VF's were the problem. Once we had only controllers of one type connected together, they all worked properly. We had no defective motor controllers.

Perhaps some of the motor controllers have a current limiting resistor in series with the LED. If the one with the lowest VF does not have a current limiting resistor, it will still prevent the other ones from turning on.

[Greg Needel]

Originally Posted by philso

We confirmed with the manufacturer that we should not have been paralleling the inputs of the two types of motor controllers we had and that the LED VF's were the problem. Once we had only controllers of one type connected together, they all worked properly. We had no defective motor controllers.

Perhaps some of the motor controllers have a current limiting resistor in series with the LED. If the one with the lowest VF does not have a current limiting resistor, it will still prevent the other ones from turning on.

The SPARK has a 150 ohm series resistor with the optocoupler's LED. If you are curious about anything else inside the spark our complete schematic is in the back of our users guide on our website. http://www.revrobotics.com/wp-conten...1200-UM-00.pdf