Victor turning on and off under load, with non-IFI microcontroller

[pludodog]

I'm trying to control a Victor (two 884's and an 883, all have the same problem) using the Arduino microcontroller. It outputs PWM signals that work fine for servos, and should work fine for the speed controller. When I vary the output with the motor disconnected the victor goes from red to orange to green as expected. When I connect the motor and give the speed controller a speed the speed controller flashes orange rapidly, and the motor makes a clicking noise, as if it were turning on and off quickly, but doesn't move.

Without the victor the motor works fine, the battery works fine, and the controller works fine. I haven't hooked it up to an IFI controller yet -- our only C controllers are in Atlanta and I don't want to remember PBASIC. I might build a timer circuit in the morning just to see, but it seems like the Victor is getting PWM signal fine.

Any idea what could be causing this?

[Vikesrock]

Originally Posted by pludodog

I'm trying to control a Victor (two 884's and an 883, all have the same problem) using the Arduino microcontroller. It outputs PWM signals that work fine for servos, and should work fine for the speed controller. When I vary the output with the motor disconnected the victor goes from red to orange to green as expected. When I connect the motor and give the speed controller a speed the speed controller flashes orange rapidly, and the motor makes a clicking noise, as if it were turning on and off quickly, but doesn't move.

Without the victor the motor works fine, the battery works fine, and the controller works fine. I haven't hooked it up to an IFI controller yet -- our only C controllers are in Atlanta and I don't want to remember PBASIC. I might build a timer circuit in the morning just to see, but it seems like the Victor is getting PWM signal fine.

Any idea what could be causing this?

I am not positive here, but I believe the problem may be related to driving the Victor with a non-IFI controller. You may need a PWM Signal Booster cable like this one:
http://www.trossenrobotics.com/store...ter-Cable.aspx

[pludodog]

I was wondering about that. Does that do anything besides boost the signal? I hooked up the speed controller to a function generator, and confirmed that the duty cycle and frequency were correct, and that I'm getting between 5 and 7 volts on the PWM output. Everything works fine until I plug the motor in, then same problem.

[RyanN]

It also sounds like your power source is not adequate to providing power to the motor and the micro-controller. I think when the motor tries to turn, it draws so much power that it resets your micro-controller, making the motor click. Using a small power adapter that plugs into the wall is a sure bet of this, but also trying to run from a small battery or a bad battery will also cause this.

[Al Skierkiewicz]

Ryan may be on to something here. Remember that a stalled motor is one that is not moving (powered is implied). Your motor will draw stall current while it is starting. You did not specify a motor, but even a small motor can draw excessive current during start.

[Kevin Sevcik]

As a follow up suggestion to Al and Ryan, there are a few ways you could test this. Setting a status bit on your Arduino that pulses once during a reset would tell you if you're resetting the controller accidentally. You could also try running a smaller motor, or try jump starting your motor by giving it a good spin in the appropriate direction before starting the output pulses to the Victor. It would help if you had the Victor in Coast mode when trying this so you could get it to a decent speed, of course.

[pludodog]

The two motors are a big CIM under a fairly small load, and a window motor under no-load. Both exhibit the same behavior, even with a bigger battery. I also have the microcontroller running under external power, so that shouldn't be a problem. It usually takes 3-5 seconds to reset anyways, so that wouldn't do it. Will the victor display red and green under any circumstances that don't mean it's receiving proper PWM signal? I guess that it would exhibit this behavior if we really turning the victor on and off really fast, instead of giving it a constant signal, but I trust the function generator...


I'm going to see if I can control another Victor in a working setup with this, but I don't see how four victors could go bad at once :-\.

[Al Skierkiewicz]

Red and green indicate full forward and reverse as sensed on the PWM input. The large (3 1/2") CIM motor draws 96 amps in stall/start. Are you using a kit battery?

[RyanN]

It's been a while since I've posted, but now I'm experiencing a problem like this on a VEX robot running a brand new Victor 884. It works sometime, and then all of a sudden it will start flashing orange rapidly. I don't have any code that would mess it up, and I'm using a normal PWM cable and powering it with a charged 12V battery rated for 3.4AH running a Fisher Price motor with some load. The voltage remains stable when starting, and it will be running then start flashing. I'm not sure what is wrong with it, right now I'm thinking defective Victor. Yesterday it wouldn't work very well at all. It would show that it was outputting a voltage, but the motor would not move at all. It's a brand new motor, brand new wire, brand new victor, etc...

[Al Skierkiewicz]

Ryan,
It seems to me that the PWM output of the VEX controller needs an interface device to run a Victor. Perhaps someone will read this and comment before I have a chance to go look it up. The most recent FP motor stalls at 56 amps so I don't think that is the problem. It really looks like the Victor is unhappy with the PWM signal.

[Rickertsen2]

Is it possible that you are sending the PWM pulse too often or not often enough for the victor's taste? If you hook a volt meter on DC up to the controller outputs, does the voltage vary as expected.

[RyanN]

Yea, I was afraid that the VEX controller wasn't being very friendly with the Victor. I have not had a chance to check the voltage as this only happens while it's running on the floor. Oh well, it doesn't really matter now. It worked for me a while back. The Victor is getting a signal I guess every 26.4ms or however much time it takes for the VEX code to go through a loop.

[Al Skierkiewicz]

My research says that Victors are compatable with the Vex controller. http://www.vexforum.com/showthread.php?t=375
That being the case, it sounds like you have a bad PWM cable or are suffering the old PWM cable not fully inserted in the Victor.

[Jim E]

I have to agree with Al on this one.

Team 1523 has successfully run FP motors with VEX controllers and Victors with no problem.

Just make sure your PWM cables are inserted properly and securely. The pinout on the VEX is a little confusing since they normally run with 4 wire instead of 3 with the IFI controller. ( Requires a custom-made cable)

Also, use a fuse block on the motor to keep everything protected.

[DonRotolo]

Just to emphasize, I have been using Victors with Vex for a while now without problems.