Our drive system uses only 2 CIM motors (we are using the other 2 CIMs on our shooter and ball pick up mechanism). All motors (5) are using Jaguar speed controllers.
On our 1st test drive everything was working pretty well, though I did notice it was not easy to rotate the (6-wheel drive) robot. It was necessary to get a bit of movement forward or back before turning was possible.
After some more work, our 2nd test session ended with both drive jaguars showing slow-flashing red.
My theory is that the jaguars were damaged by pushing the unpowered robot around on its wheels with the jaguars still connected. Team members report seeing the lights on the jaguars lighting up while they were pushing it around.
Anyhow, it’s all bagged up now, but I need to figure out what to do when we get to the competition. I think the next step to correct the problem is to swap out the speed controllers. Hopefully that will fix it.
We don’t have any more jaguars, but we have a bunch of victors.
We’re not using CAN bus, or any special jaguar features.
So… should we rearrange so that we have jaguars on the drive, or just put victors in for the (presumed) damaged jaguars?
Also, is my theory of how the jaguars were damaged a reasonable or probable one?
It sounds to me like your drive system draws a lot of current when attempting to turn. As you wear down the battery, this is more and more likely to throw the Jaguars into a low-voltage fault protection (indicated by the flashing red).
I would guess that the Jaguars are not damaged. Many teams roll un-powered robots around like this. You will see enough power back-fed into the system to light up the Jaguar LEDs, but in my experience it is difficult if not impossible to back-feed enough voltage/current to damage things.
The potential solution(s) would be make your robot easier to turn by reducing friction on one or more sets of wheels, reduce the current draw by increasing the gear reduction (less speed more torque) or if the system works OK for 2.5 minutes of driving on a fully charged battery, be prepared to swap batteries every match.
It sounds like the drive train gearing & traction/turning friction are too high.
The red flashing means that the Jaguars are sustaining over-current and shutting down to protect themselves.
It isn’t related to pushing the robot around and getting back EMF to light up the Jags. You really don’t see much power that way.
It’s the CIMs operating at stall (133amps) for too long, and the Jags clamping down on that.
Victors will improve the situation somewhat as they have more tolerance for stalled CIMs, but you may want to consider either dropping the middle wheels more, or changing the sprockets to gear the drive train down.
I don’t know exactly. It is the CIMple gearboxes, but those drive small pinions and in turn chains and a set of larger sprocket gears at each wheel.
I had mentioned the possible need to go with larger sprockets, but the team did not look happy at that prospect. I still think it may be needed…
No.
I hadn’t though of that. On a hard surface it turned very easily, but the test drive was our first time on any sort of carpet. I’m not sure how much work it will be to drop those center wheels down more.
If our wheels are not air-filled, that is not likely to help?
The strange thing is that it was driving around pretty well just the day before… On the 2nd test drive it started out Ok, but then after trying to go over the ramp once, all we could get was flashing red. We tried a fresh battery, but it was all the same, even just trying to move straight forward.
One thing the Jaguar FAQ mentioned is a too-tight chain. I remember working pretty hard to get those chains on. How much of a factor might that be?
Dropping the center wheels further will help greatly, if that is the problem. Of course, too much drop and you’ll have a bot that rocks back and forth.
One thing the Jaguar FAQ mentioned is a too-tight chain. I remember working pretty hard to get those chains on. How much of a factor might that be?
If the chain is so tight that it doesn’t budge at all when you try to wiggle it, it is too tight. Tight chains add friction.
I’d just like to point out something about this situation.
First, let me be upfront and say I’m not the biggest fan of Jaguars, I prefer Victors because I find them simpler, smaller and generally more robust. I also find that they can take more roughhousing than the Jaguars, which give up somewhat easily in my opinion.
That said, your Jaguars are trying to tell you something, if your system is constantly going in to fault mode and shutting down, your solution should not ever involve getting rid of the device that is shutting you down in favor of one that will ride things out until the (bitter) end. It is faulting out for some reason and you should stop to think about what reason that is. Perhaps the Jaguars are giving up too easily, but I suspect (as others have suggested earlier) you have a legitimate problem.
Bottom line, if your robot is complaining a lot, it might just be whining, or it might be warning you about a problem before it’s too late!
I think you’ve already learned this lesson, but I just wanted to reinforce it.
That should not be possible if everything is properly hooked up and insulated; the wires should be insulated right up to the point where they meet the Jaguars making shorting impossible. With other motors, This is more likely since unshielded female spade connectors can shake loose and come into contact, but these shouldn’t be needed with CIMs
your Jaguars are trying to tell you something, if your system is constantly going in to fault mode and shutting down, your solution should not ever involve getting rid of the device that is shutting you down in favor of one that will ride things out until the (bitter) end. It is faulting out for some reason and you should stop to think about what reason that is. Perhaps the Jaguars are giving up too easily, but I suspect (as others have suggested earlier) you have a legitimate problem.
^^^ Quoted for truth. If time and resources permit, find the root cause of the problem and fix it.
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Im not sure why your getting this error but if it makes the jags not work on other systems this might help you to get them running again.I helped fix a similar problem for another team through firmware this year. Their robot encountered the problem when running two cims and using pwn were their jaguars acquired flashing red lights and would not function. I was able to fix their problem using the bdc-com updating tool that the jaguars use for firm ware. to do this:
1.install bdc com on your computer (you can find it on texas instruments sight somewhere)
2.install black jaguir firm ware (i assume your using black jags, if your not you have to make a can connection between the jags)
3.use a db9 to rj11(phone line) cable and connect your computer into the correct can port on the jag,
4.you need a terminator plug so either borrow one at regional s or solder a resistor between the green and red wires on on some phone line then put that into an rj11 crimp
4.5.plug this into your jaguir
5.go to bdc com and see if in the upper right hand corner you get an error called gate fault.
6.if you do have a gate fault reset the jaguar to factory default
7.install black jag 101.bin on your jag
8.it should be unbricked. and the red light should go away
9.if you get the error “cannot access the boot loader” you have to use the reset button to manually factory reset the jag. then use black jag 101.bin on the jag.
Im not 100% certain how the gate fault error happens, i was not there to see this team break their stuff. But by messing with the jaguars firmware through a can to computer serial port hookup i was able to make it work for them again.
or you could just switch to victors, easier solution :yikes:
-note if you don’t have the gate fault error im not sure if the firmware reset will help you.
We have abandoned Jags in favor of Victors two days before bag-day!
Apparently this is a yearly tradition on our team :o
We also started with 6 wheels, 2 CIMs on CIMple boxes and had friction issues on carpet. Covering wheels with duct tape worked but not cool, so we eventually lost the midddle wheels. The Jags kept cutting out, the Victors don’t.
Jags have 2 MOSFETs per H-Bridge link, Victors have 3, and I don’t think Victors have a cuttout like the Jags.
I agree with prior comments that this is NOT the way to solve this problem as Jags (one assumes are designed corrctly…) are cutting out for safety reason. As a result we can “fry an egg on the CIMs”! and we can barely make it through a match on one battery.
Turning from standstill is the biggest current drain - 90A per CIM!
Moving first helps a lot.
I suspect that 2 CIMs is simply too weak for a 120lb bot. Gearing down would be the best solution for us, however its bagged…
Jaguars are 4 years old now and they are still so fragile?
We are having fits with the Jaguars. I have been attributing them to some CAN related collateral damage but after reading this thread, I am starting to think that Jaguars are just not safe to use. Seriously.
I do not want my speed controllers “protecting” me by shutting themselves off. If they can’t take the heat get the heck out of the FRC kitchen!
This is killing us.
I will have some choice words for FIRST Engineering after the season but man oh man has FIRST a lot of ‘spainin’ to do…
As a suggestion, 1 CIM per side without a shifter and with anything approaching grippy wheels is probably going to be a stretch to keep from over working the CIM or the Jaguar (or Victor) or (most likely if you fix the other problems) the 40A Breaker.
I suggest you buy two CIM-Sim from AndyMark or a CIMULATOR from Banebots and use one of the excellent 550 motors that are legal (one of the many FP motors or Banebot 550 motor… – in general the more power the better) and buy another two Jaguar or (better yet, given my GAH!!! in the message above) two Victors.
If you install this on your CIMPleBox in parallel with your CIM you will have more power to turn but more importantly in your case, you will have two current paths – and since loses are an I^2 R problem, halving your current can effectively quarter your electrical heat dissipation.
And, as long as you can wire up the speed controllers & press the gears on at the competition , everything is COTS so it doesn’t count on the 30lbs allowance (of course you still have to make your 120lbs limit but one battle at a time…)
Formula is correct, application is almost correct.
The *total *current didn’t get halved, it just got split into two paths. So, if everything else is the same, the power dissipated per path is a quarter of the original, but you have twice as many paths, so the total power dissipated (lost) is half the original (which is still a good thing).
To put it another way, putting another identical load in parallel with the first means your R is cut in half, which directly says that the power is cut in half.
Also, I just said “if everything else is the same”, but if you’re changing motors and/or gearing, then everything isn’t the same. If new motors or gearing gives you a better match of motor to load, then that will be where you see the biggest improvement, and heat caused by losses becomes a smaller issue.
You are right, I was sloppy. But here is the thing. It is heat that ultimately kills the electronics. If you halve the current per leg, then that leg is going to see much less than half (~1/4 to first order) of the heat it would have otherwise seen.
So from a stress your electronics pov, it is a better than halving. That was my point, which I think is still valid.
We exclusively use victors. We gave them another chance last year, but they proved too unreliable. Ensure your mechanicals systems are designed and functioning correctly, but don’t rule out the jags as the root of your problems.
Our students keep asking if they can recreate the office space copier scene with jaguars. After the pain they caused us, I’m reluctant to say no.
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