Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

I've been following this thread for some time.. However, I have yet to read anything that definitely shows that Denso Window Motors and Jaguars don't work well together.

In 2007 we had some issues using Window Motors on our lift. As such for this season we are hoping to use the advanced monitoring of the Jaguars and CAN to watch voltage draw etc... so we don't burn out, or over tax, or even gain an indication of a failing motor. Of course our lift will be different, and hopefully significantly better than 2007's.

However, if it is very clear that Jaguars won't meet our needs then we'll switch to victors.

Anyone?

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

Michael,
It is well documented that the window motors react with the Jaguar. Several teams have documented the issue but I believe it was GDeaver and John Novak who really tied it down. It would appear to be an issue with the anti-back drive assembly in the window motor. This year's rules allow the removal of that assembly for just this reason.
<R47> Motors and servos used on the ROBOT shall not be modified in any way, except as follows:

C. The locking pins on the window motors may be removed.

Thank you to those that made us aware of the problem. I apologize if I left a contributor's name out.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

is there a procedure for removing this pin?

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

Thanks Al, GDeaver, John Novak, and everyone else that has contributed to this.

Given the definitive "issues" we'll be using Victors, as the anti-backdrive is a feature we need in our design.

Again,
Thanks everyone

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

I have not performed this operation. John Novak gave me the impression it was pretty easy once you have the motor apart. I am guessing they are very similar to the pins in the drill motor transmissions we used in the early years or the NBD transmissions.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

The jag denso issue goes beyond the locking pins. There must be a problem between the Jags high frequency PWM and the PTC in the Denso motor. We had problems with premature shut down with both back and tan jags with the locking pins removed. The problem was not as frequent with the locking pins removed. We had no problems after we went to victors. this is a link to our website and a page that shows some pictures of the locking pins.
http://wiki.team1640.com/index.php?t...r_Locking_Pins
After we changed to victors our pivot steering motors work wonderful. Don't think FIRST will go for bypassing the PTC. We did not try this.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

I have to say our experience with Denso motors has been very predictable. Every time we used them with the locking pins in place they exibited the same problem with either Victors or Jaguars. Our most recent application was independantly steering wheel modules. When they encountered a "spongy " load such as rubber tread on carpet or a soft plastic stop, the energy absorbed would backdrive the motor and set the locking pins. The only way to unlock the motor was to drive the pins back out of the lock condition. This was impractical with error based steering algorithms. As soon as the pins were discovered and removed, The motors performed absolutely predictably with Jaguars. This means that if the motor was stalled due to a restriction, the internal thermistor would heat up in a few seconds and the motor torque would be reduced to the point where it would no longer turn. as soon as the thermistor cooled down the full motor output returned. we went through three competitions with this combination and the only time this happened was when a chain came off and jammed one. Under normal conditions the motors never faltered or even warmed up after 20 minutes of constant driving. The same held true on our backup robot with gray Jaguars. CAN was used in volage mode throughout the season.
Thanks to GDeaver for the pictures at the link above of the motor disassembly and pin removal. This is absolutely essential for reliable operation with varying loads. Beware that when the pins are removed the gearmotor will backdrive very easily. It will not support a load although a motor this small probably shouldn't be driving an arm anyway.
I will be glad to elaborate on the pin removal or anything else that is unclear. Just keep in mind the motor power and efficiency of a worm drive when applying these.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

Sorry to bring this thread to life again, but... :)

We have a dual window motor arm joint this year. Bench testing was great, we removed the locking pins and had no problems with lock ups. Now that is in the bot, the arm is locking on the way down. If we bump it up, sometimes we can get it to free up and go down. I am not too smart on the inner workings of the worm drive and such. We are at crunch time and need to figure out if this is an internal lockup, or if the speed controller is playing in to this. Drum roll please, we are using the new black jaguars with it.

I don't think we have any more victors available to try, but after reading this tonight I will do another search tomorrow to see if we can dig up 2.

Is it still the general consensus of this thread that the jags should be swapped out for victors when controlling a window motor under load?
Thanks

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

iam,
You might try adding some counter balance to the arm joint to help prevent jamming the worm drive in the window motors. It can take the form of surgical tubing or springs. If you have removed the pins, the only thing left is the worm drive.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

While I'm no electronics expert, I have to say that I can't disagree with the statement that a problem exists specifically while using a window motor powered by a jaguar that doesn't exist while using a victor speed controller. Last evening our arm (powered by two window motors) exhibited the exact issue being referenced in the thread. We switched to Victors from the Jaguars and the problem disappeared completely.

Should we switch to spikes?

Thanks, Charles Baxter

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

Charles,
Your mileage may vary but several teams had reported differences last year in window motor operation between the two controller types. John and Gary seem to have researched this very thoroughly at the end of last season. I can see that the mass of the pins could be effected by the high switching frequency of the Jags in certain applications. However, as Gary points out, there is a PTC thermal device that may also have a significant effect. When one rules out everything else, it has to come down to motors themselves. I should have pointed out above that there are differences in the left hand vs. right hand motors. If used in opposite pairs, there may be binding in the two transmissions with these differences. Your design may have a more pronounced effect than your neighbor's robot.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

With our Arm, we are using 2 Window Motors (with Victor's) through a 4.8:1 Gear reduction to a arm that weighs about 15 lbs (I think) and we are delivering about 61 ft-lbs of torque with 2 rubber bands on the back. We have measured the current going to each motor during normal operation and it is around 11 Amps each at full load I believe. According to the motor specifications, the Denso motors will stall at 18.6 Amps.

This may be within your acceptable range, but I would be wary of controlling an arm with no speed control. Unless you are really good with keeping it counter-balanced I think it would be very jerky in operation. We can run our Arm for about 25 minutes before the window motors shut down to temperature. When our fans are running on the window motors (normally) we have ran the robot for 8 hours a few times during driver training and the motors are cold, with no problems at all.

EDIT: We did not remove the locking pins, as we wanted the arm to hold its position without having the motor hold it there.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

That is only on one motor, the opposite type is speced at 21.5 amps stall.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

Indeed.....

We are using two Densos through a CIMple box, driving a chain onto the pinned fulcrum of our arm. Previously, we ran them with the new MDL-BDC24s. We had problems with the thermo-resistors cutting out and the arm wouldn't move.

Today, we swapped the Jags with Victors, and they run like a fine watch, or at least as good as you can get with unavoidable backdrive....

Before anyone asks, the code was correctly written both before and after.

Thanks all!