Re: CIM speed in reverse?
 

If it worked right on the table but not on the floor I think you still have a problem. The dead Victor may be a symptom and not the disease. Anytime a drive works in the air but not on the floor, start looking for misaligned parts in the drive. Bearings that are not parallel ( on two ends of a drive shaft) is often the problem. Those that use chains often put too much tension on the chains. Remember there are very few of the kit motors that can stand any side load and therefore need to be coupled to shafts and bearings that can take the load. i.e. Don't put a chain sprocket on the shaft of an FP, drill or Chalupa and expect it to last.

Re: CIM speed in reverse?
 

Al,

In general, you are correct. However, for this particluar case I think the Victor was the problem. They are using the drills and CIM motors together matched at free speed. If only one victor was bad, then one of the paired motors would still work. While in the air (aka almost at free speed), the side with one motor would still look like it was running with two due to the matching. But once under load, the problem becomes clear. This exact method is how we have found bad Victors (or disconnected wires) in the past.

-Paul

Re: CIM speed in reverse?
 

Paul,
Wouldn't there have been a noticeable difference in speed if one of the motors were not driving, even in no load? I guess the effect would have to depend on which motor was nonfunctional vs. it's ratio to the final output.

Re: CIM speed in reverse?
 

Al,

You would think that the one side would move slower due to the fact that one motor had to actually drive the dead one. The fact is, even though it does move slower it is very hard to tell by eye if it is slower. If I understand where you are going with this, you are right that this problem could have been detected on the table.

This next part is to everyone else (Al's team already does something similar to this and they probably taught us this at one time),

A procedure we do every year is to check the current draw of each motor when the drive base is up in the air. It is rather easy to do. Simply put an ammeter (or multimeter set to current) in series with the motor and measure the current draw of each motor. The CIMs on each side should draw the same current and the Drill motors from each side should draw the same current. You would have found the Victor problem from this test. We do this test to make sure our gearbox is the most efficient it can be and to make sure we do not have a bad motor, bad connection, bad speed controller (Victor).

If the above procedure was done while the robot was in the air, then you would have noticed the problem.

-Paul

Re: CIM speed in reverse?
 

Using a multimeter was how we actually found the problem. The victor was tricky :rolleyes: ... light were lighting up right but when we tested the current going to the motor it never changed when we moved the joystick...

i of course blamed the code for it couldn't be my wiring :D , but thanks guys, it always does turn out to be something silly

Re: CIM speed in reverse?
 

Sorry about the delay in reply. This is really an unusual failure for a Victor. Can you detail how you measured the current? Were you tripping breakers? Do you still have the controller or did you return it to IFI? I would like the chance to check it out.

Re: CIM speed in reverse?
 

Al is right!
I've never heard of a transistor jumping to saturation before. have you calibrated that victor lately? Al, if you get any info, tell me please!!!

PS: Read my signature. Amazing as it sounds, many electrical failures were because of it, and I have seen some weird things when I fix stuff.

Sparks

Re: CIM speed in reverse?
 

1.) We measured the current by propping the bot up on boxes and running it forward, then we hooked up a micrometer to the 2 screws that went to the motor and it was reading 0 volts. We checked the code and everything was in place.

2.) I really doubt we were tripping the breakers, there was no resistance since it was propped on boxes. Plus when we installed the new Victor it worked, so that was the problem.

3.) Yes we still have the Victor, actually we put it back in the working victor box for unknown reasons. If you would like to check it out, PM me details to send it to you.

Re: CIM speed in reverse?
 

The Bobcats have encountered something similar. We had a few issues where a Victor gave us no output. We would see a flashing LED (as if the controller was not powered).

We replaced the Victor and everything was OK. However, we checked the "bad" Victor and it would check out OK... Further checks and we found that the PWM cable was not seated fully down in some of the Victors.

This was NOT a bad cable problem. We would install a 1' PWM extension cable at the Victor end and the problem would go away.

Does this sound familiar to your problem?

Re: CIM speed in reverse?
 

Not really, although I am not 100% sure, I think that the LED lights were lighting correctly according to the joystick movement.

Re: CIM speed in reverse?
 

Colt,
A multimeter might not measure any output voltage on the Victors until they are at full throttle. (Indicated by a steady RED or Green LED) Depending on the meter you use it may not be able to measure the pulsing AC waveform sent to the motor. If you were at full throttle then a DC meter should indicate approx. 12 volts. An oscilloscope would indicate whether pulsed output was available but be careful to not ground the output of the Victor when using a scope. Connect the ground lead to the "-" screw on the input to the Victor and then probe either of the output terminals for a display. Only one will show output this way for forward and the opposite one for reverse.

Re: CIM speed in reverse?
 

Ah, yes, I forgot to mention that we pushed the joystick forward full throttle with the LEDs solid colors when we were testing the volts, which read 0v.

Re: CIM speed in reverse?
 

Al,
I think the victors put out DC.
They take in PWM and DC, and the motors are DC, so I don't think they'd have AC coming to the motor. I think it's simply a steady variable voltage going to the motor. Pulsing a motor will shorten its life considerably.

Sparks

Re: CIM speed in reverse?
 

The speed controllers do not have the room for a smoothing inductor capable of such amperage. The inductance of the motor provides for a rather smooth DC current but the DC voltage is chopped at a fairly high frequency.

Almost all variable speed motors (DC or AC) use chopped (PWM) waveforms.

Re: CIM speed in reverse?
 

Sparks,
The controllers are capable of pulsing battery voltage to the motor at full level with a PWM type signal. As the length of the pulse gets longer the average current in the motor goes up. At full throttle (when the LED is "on" steady) is the only time that the controller puts out a pure DC signal. If the controllers were to put out a varying DC voltage they would have to dissipate the difference in voltage between what the battery puts out and what you want to send to the motor. At low throttle near stall, that could be considerable heat to get rid of. One of the nice effects of this operation is that the motors are pulsed at full voltage and therefore easily overcome starting frictions and torques. I can go into a more in depth desciption if you would like. They are really pretty cool little animals.