Victors for Chips Cutting Off

[aaronbr28040]

I posted a question in the motors section of the forums about the dimensions of the clutch spring earlier, now we have found that rather than a mechanical problem we are having an electrical/control system problem. We are having problems with the Victors going to the Chips cutting off at 9 volts. The Victors for the Drills and the Chips are running on the same PWM cable (one of the Y-cables supplied with the kit) Both of our chips (atwoods) are doing this. Does anyone have any suggestions as to why this is happening?
Thanks,
Aaron

[KenWittlief]

cutting off at 9V? do you mean its only putting out 9V at full throttle, instead of 12?

you might need to calibrate the victors

are you sure you code is putting out 254 and 0 for full FWD and REV?

are you sure your battery is not going dead?

one other thought - if you are seeing 9V on the output of the victor make sure there really is 12V onthe input side with the motor running - maybe you have a poor connection somewhere in your power path - those big wire blocks need to be tightened up good to get a solid connection.

[aaronbr28040]

cutting off at 9V? do you mean its only putting out 9V at full throttle, instead of 12?

you might need to calibrate the victors

are you sure you code is putting out 254 and 0 for full FWD and REV?

are you sure your battery is not going dead?

one other thought - if you are seeing 9V on the output of the victor make sure there really is 12V onthe input side with the motor running - maybe you have a poor connection somewhere in your power path - those big wire blocks need to be tightened up good to get a solid connection.
We checked the input voltage and it is 12VDC. We do not reach full throttle before it cuts out at 9 Volts. It is only the Chip and Victor on one side (we are running a dual motor, drill and chip, transmission on each side) causing the problem. Our battery is fully charged and has been changed and the problem is still there. I have checked with the programmer and even had him do a full forward in program mode. The Chip still cut off at 9 Volts. He has also reassured me that the code is set for 254 and 0 for full FWD and REV. Any other suggestions would be greatly appreciated.
Thanks,
Aaron

[KenWittlief]

Im not sure what you mean by it cuts off at 9V?!

do you mean as you speed up, once you get to 9V on the output the victor goes dead? the motor stops? the circuit breaker breaks the circuit?

or do you mean the output only goes up to 9V and no higher?

if the breaker is tripping then I would think your motor is binding - something in that part of the drivetrain is too tight and the motor is drawing enough current to trip the breaker.

are you powering both the drill and the chip when this happens?

are you using the drill motor gearhead that came with it? are you sure its in low gear and not in high?

[aaronbr28040]

Im not sure what you mean by it cuts off at 9V?!

do you mean as you speed up, once you get to 9V on the output the victor goes dead? the motor stops? the circuit breaker breaks the circuit?

or do you mean the output only goes up to 9V and no higher?

if the breaker is tripping then I would think your motor is binding - something in that part of the drivetrain is too tight and the motor is drawing enough current to trip the breaker.

are you powering both the drill and the chip when this happens?

are you using the drill motor gearhead that came with it? are you sure its in low gear and not in high?The motor cuts off at 9 Volts (the speed controller goes dead and stops giving power until the voltage is dropped back down). The motor is not tripping and the gearboxes are not binding. We are using the drill motor that came with it and it is in low gear not high. I have doubled checked all of this along with an engineer and two other mentors. Any other ideas?

[KenWittlief]

I wonder if the drill motor is spinning the Chip faster than it wants to , turning it into a generator, and putting 14 or 16V or more onto the motor side of the Chips Victor? maybe that is causeing the Victor to wack out?

Do I understand this correctly - you have a voltmeter on the output side of the Chips Victor, and as you ramp the speed of the transmission up, once it gets to 9V the victor goes dead? what does the meter say then?

is the drill motor still spinning the Chip when this happens?

[KenWittlief]

if you disconnect the Chip from the victor and put something else on it, like a loose drill motor or a globe motor - does it work correctly then?

[aaronbr28040]

The Chip cut off with me holding it in my hand, not in the transmission. We swapped the Chip and drill motor Victors, and the problem followed the Chip to the new Victor. We're now seeing the problem happen on both Chips.

The latest vague theory is that noise from the motors is messing with the PWM signal.

(This is mentor Charlie, signed on as Aaron.)

[KenWittlief]

thats possible - can you wire separate PWM cables to the two victors? instead of the Y cables?

[aaronbr28040]

thats possible - can you wire separate PWM cables to the two victors? instead of the Y cables?We have tried replacing the Y cables with two seperate cables and the problem still persists. Thanks, Aaron

[KenWittlief]

do you have the fans hooked up on the victors? maybe they are overheating and going into thermal shutdown?

Ive never heard of this happening before - not with a motor that has nothing connected to its driveshaft

[KenWittlief]

oh, wait - by any chance do you have the pwm wires tiewrapped to the power wires going to the victors? so they run together their entire length?

you need to keep the pwm cables away from the power wires as much as possible.

[Charlie B]

We physically removed the transmission, with drill motor and Chip, from the robot, (no electronics), and hooked them up to our 2002 Pbasic controller and Victor 883's. The Chips still skip. Two possible explanations I can think of...
1. the drill motors are backdriving the Chips and freaking out the Victors. But, Innovation FIRST says that the Victors shouldn't care, our ratio is 3.5:1, which is very close to the ratio we used successfully last year, and I remember feeling the Chip twitch while holding it my hand, out of the gearbox. Maybe I was hallucinating from fatigue. We'll see if we can get it to fail outside of the gearbox again, and we'll try loading the Chip to get it to work harder.

2. noise. PWM's and power cables are in close proximity on both this year's robot and our 2002 robot. It seems unlikely that we could so easily duplicate a noise problem on a completely different set of electronics, but maybe it's so. We'll try moving wires to separate power from signal.

If anyone has any ideas, we're all ears.

[Charlie B]

We finally found the problem. DUMB mistake. The drill motors were in low gear, when they were supposed to be in high gear. The Chips were drawing 60 amps trying to speed up the drill motors, and breakers tripped. 20 or so hours wasted. What a learning experience.

Thanks for the help!