Could a magnetic field around CIMs cause fuses to blow?
 

Could a magnetic field around CIMs cause fuses to blow?

After testing our drive train for the first time we noticed some strange behavior from one of the CIMs and the Victor controlling it. We are using the gearboxes and the CIMs from the KOP.

When we started testing our motors we noticed that whenever we tried to turn a fuse would blow for one of the motors in the gearbox on the left side of our robot and the right side would begin to struggle. This happend wether the robot was on the ground not. We decided that we should isolate the problem by testing one side of the robot at a time, so we pulled out the fuses for the gearbox on the left side. When we drove the motors on right side we noticed that the cooling fan on the Victor of the motor that had been blowing fuses began to spin, and the Victor's LED came on. This seemed very odd because the cooling fan only came on when we drove the rightside motors. I noticed that the black wire for this "problem motor" was running directly under one of the motors on the rightside. I began to wonder if the magnetic field generated by the aperture of CIM could be powerful enough to induce a current in this cable. If so this would explain where the power was coming from to power the fan on the Victor. Could this also explain why this motor was blowing fuses? Jay(a team mate) and I speculate that the magnetic field around the CIMs could have caused a large amount of resistance in the problem motor's cables whenever we tried to turn. Does this explain our problem? Are we crazy?


P.S. We tried to reproduce the situation and use a multi-meter to measure the voltage produced but failed to get any definative results. I think a science teacher at my school has some sort of meter(EMF meter I think) for measuring the strength of magnetic fields so we should have some measurements by monday. Also here are some pics of our gearboxes and the wiring to them.
Picture of the wiring
Picture of the motors

Re: Could a magnetic field around CIMs cause fuses to blow?
 

As clarification of what Scitobor said, the sensor measures the Magnetic Field Strength in guass. This is distance sensitive, but will tell you if there is a strong magnetic field, or even a weak one. I used it on by science project. But it only goes to about 1000 gauss or .1 Tesla or all you tech heads

Re: Could a magnetic field around CIMs cause fuses to blow?
 

I would expect behavior like that from a short in the wiring. You could be back-feeding current into the speed controller for the unconnected motor. I have never seen a current like that induced in a wire on a FIRST robot, so before you chase the rabbit with the emf meter, check your wiring. Using the ohm checking capability of a multimeter, check for continuity where there shouldn't be continuity (i.e. motor wires on opposite sides of the drivetrain)

Re: Could a magnetic field around CIMs cause fuses to blow?
 

Backfeed was prevented, we tested the robot while it was off the ground so the left motors were not spinning at all and the fuses to their Victors were removed leaving only one possible power source... we think.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

How did you prevent backfeed? I don't think the motor is powering it, I think it's a short. Disconnect the input side and rerun the test, then if it doesn't do anything, disconnect the output side wires and reattach the input side.

Also, I didn't notice the picture before, but you are grounding the electrical system to the frame, something I don't believe you are alowed to do. Disconnect your groundstrap and see if the problem dissappears. The groundstrap could turn a harmless short of one of the terminals into a nightmare.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

Hmmm... An induction spike through a magnetic field? Interesting thought...

On the whole, I don't think so. It would need a pretty strong field (one I don't think the CIMS can create) to screw with the fuses in the ways you are describing. Theoretically speaking, you could do it, but it seems unlikely at best. Have you tried relocating the victors? That's the only real way to tell.

Sparks

Re: Could a magnetic field around CIMs cause fuses to blow?
 

The frame is not being used as a ground, the motor's wire was disconnected and is pointing straight up. Sorry I was not very clear, backfeed was prevented by removing the motor's wires from the Victor. When we did this the Victor no longer came on as it had before. We know the power is not coming from the power supply because if it were it would be getting constant power and not power only when we run the right side motors.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

Looking at the picture more, I see another issue. Remove the button heads on the speed controllers. They are too large and several of your connectors are touching the heads or are near to touching the heads. The best solution is to use nylon or some other type of plastic fastners. Check your wiring for shorts, and I believe your issue will be solved.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

One theory that we had was that the start current was above the 40A and caused one moter to go, and that forced the other moter to start two moters worth, and that caused it's fuse to go, but it doesn't explain what happened when we isolated the offending victors electronically. And it doesn't happen on both sides. I don't think, I wasn't around for it all.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

We isolated/removed every known power source so I'm not sure what else could have caused the Victor's fan and it's LED to turn on only when we drove the right side. I also felt that the field would be too weak to cause this but we eliminated all known power sources which caused me to come to this conclusion.

While this is true this does not explain how the Victor was being fully power while its fuses were out. Also, the connects on the offending Victor are no where near the screw head.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

We checked and double checked for shorts, partly because we had trouble getting both sides to run with one joystick drive (but it was becuse IFI Loader was set to the default hex and not the new hex.)

Re: Could a magnetic field around CIMs cause fuses to blow?
 

Yes it can. Two years ago, we (ie professionals) welded our frame while the electronics were still mounted. Pretty much everything fried and we lost $1000 replacing the RC, victors, spikes, fuses, etc.

Say no to big EM fields around the FIRST electronics!

Re: Could a magnetic field around CIMs cause fuses to blow?
 

We already had our frame welded, but there arn't any shorts we can find. As I had said, we checked everything twice to find something wrong. We're just stumped.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

From experience, problems can often be fixed by fixing seemingly unrelated problems. I would advise that you try the following. It is what I would do if I was there.

Set a multimeter to Ohms

Put one probe on the frame. Use the other probe to check other spots on the robot such as the terminals of speed controllers. They should be isolated, but I suspect they are not.

You should also try removing all of the motors from the output side of the speed controllers and make sure the terminals are not touching the robot. The problem lies on the output side of the victors. This has to be true due to the fact it only happens when you run the motors on one side.

If the problem no longer occurs, connect the motors one by one and look for the problem. You may be able to isolate it.


Another thing you may want to consider is that you could have mixed the motor wires up. The fuses could be blowing because the motors are running in opposite directions in the same gear box.

To test this, remove all of the motor wires but the ones going to one motor. Run it and see which direction the wheels move. Then, disconnect it and run a different motor similarly, if they run the same direction, attach both motors to their speed controllers. Do this for both gear boxes. If one motor in a given gear box runs in a different direction than the other, reverse the polarity or revise the program.

One thing you need to keep in mind is that the victors can be powered through the output side. If you push the robot on the ground, the controller and the victors will all light up because the motors act as generators.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

A welder is a little different than a few camper jack motors.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

We'll try it, along with the magnetic field thing, but the moters seem wired right. Unless they put the wires backwards on the moter itself.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

We are certain the motors are running in the same direction in the same gearbox, each gearbox alone ran fine. However, the shorts could still be a problem, we will have to check monday.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

It won't hurt to double check it. I've had it happen and it will seem to work fine, but It really isn't. You could probably use an ammeter to check for excessive current draw as well. Good luck, hope I was able to help.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

<anouncer voice> Will team 617 discover the problem with their victors in time? Will they have to do something drastic?! Tune in Monday afternoon to see the exciting conclution to this perplexing problem! </anouncer voice>

Re: Could a magnetic field around CIMs cause fuses to blow?
 

One problem i suspect is you may be using the wrong equiptment with the cim motors. With the Atwood/CIM motors you should use the victor motor controllers between the power source and the motors (which you are using) but what should be bridging from the battery to the victor is a 40amp self resetting circuit breaker. You should only have fuses in the Spike Relays. Below you should be using the ones on the far right at the top of the breaker board for the cim motors.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

I'm pretty sure they're doing that. Regardless, the motors shouldn't draw enough to trip the breaker (or a 20 amp fuse) when it is off the ground. It probably shouldn't draw more than 6-8 amps. You should read the entire thread, the breaker tripping is the result of the problem, not its cause.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

We are using the 40A self resetting circuit breaker, but becuase theres the breaker panel and the main breaker, we say fuses because they are like the old fuses. They look like them and the almost work like them. The big difference is that they do reset and so you don't usually need to replace them.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

if infact you have 4 wheel drive and too much traction the motors will stall and the breakers will pop

Re: Could a magnetic field around CIMs cause fuses to blow?
 

It's two wheel dirve and it's off the ground so there isn't any load except the transmission and the chain.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

OK,
First things first. You first picture clearly shows a wire going to the gearbox and it looks strangely like the red lead of a Chalupa motor. This is a big no no and you will not be able to compete with this arrangement. Next you have a screw missing from motor(+) on one of the controllers which leads me to believe you using a common ground or are wiring motors in series. This is also not allowed and will not work if you plan on backing up. The motor leads on the controllers change polarity, i.e. sometimes the motor(-) is battery negative and sometimes it is battery positive. Lastly, as someone has pointed out, the mounting hardware on your controllers is touching motor(-) again giving a sneak path to frame. 4-40 allen screws work OK but tywraps work and are non conductive.
So what was happening? If all is as I surmise above, the motors on the left side are reversed so that the robot can drive forward. With the polarity reversed and the motor and controllers touching the frame, the output of the left side controllers are shorted when driving forward. The opposite condition would be the case if you were driving backward. Make the suggested fixes and try again. That is how the LEDs on the disconnected controllers were lighting when you ran the right side.
As to the question about magnetic fields...the answer is no. Yes a wire in the presence of a magnetic field may have current induced in the wire. This is dependent on two things, the magnitude of the field and the field must be changing or the wire moving. Since the motor is a permanent magnet, the field is not changing, and since the wire is not moving there can be no current induced in the wire. Since the motor leads are connected to a fairly low impedance, any induced current would be tiny compared to the motor run current.
If you have any further questions you can always PM me. I won't have an immediate answer but I will get back to you. Anyone can ask me questions and I will try to answer.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

This isn't criticism, only addressing all of your concerns.

The wire that looks like it is going to the gear box is just diconnected from anything. it looks like it is on the gear box but it is just over it. But it does look like it.

The screw is out becuase we were disconnecting things, and we pulled the wire out for that moter.

We see that, and we will check it out when we get back to check the robot. but it would seem odd that several wires would be doing the same thing and creating this problem

I agree that it is far fetched, but when isolating everything, that was about the only thing we could think of at the time. As far as no magnetic field changing, some magnet has to be moving for the moter to go. But it still seems unlikely.

Thanks for you help. All options will be considered. We will look at everyting on Monday when we get back to school.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

Believe me there is no moving magnet. All of the KOP motors have stationary, permanent magnets. The Chalupas have two large curved magnets inside the case and glued to the case to keep them from moving. The armatures move when current is applied to them but the magnetic field lines up with the filed of the permanent magnets for the most part. The brushes are doing the appropriate switching to make the fields line up. If nothing else is wrong, the hardware touching the motor(-) screw is enough to cause your problem. I think if you fix the hardware you will be much further along, if not curing the defect altogether. Remember that some controllers are reversed and they are dumping current into the frame. Try this, take you meter and with the robot power removed, check for continuity from the frame to each output terminal on all your controllers. You should measure infinite resistance for every terminal. Then move the probe to measure the +12 volt lead at the output of the main breaker. It should also be infinite. Finally, measure the input to the main breaker (off Please) and you should again have a infinite resistance. If none of these tests are infinite, find where the path exists and remove it. Let me know what you find.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

I just checked the bot. There IS a slight short with the screws in the victors. The resistance isn't infinate, but it is in the 1000 K ohms. The multimeter didn't beep when between the terminals but did between a screw and a termainal. This will be fixed, but I don't know if that was the whole problem.

I rechecked again with someone looking and found that the screws arn't conducting to the terminals. I found that while the wires are distint and not crossed, all of the positive red wires are conducting for each other. I tested from the breaker panel to the victors and all of the red are conducting from each part on the panel on the 40A fuses. I don't know how this works. I can't find any grounds anywhere near the victors. The red wires arn't connected tot he balck wires, but all of the black wires are connected together like the red ones. We are going to re-wire it to track down the culprit. If you have had trouble like this or know what is happening, this tr4ead is still going until there is a cure. In other words, We need more help :D

Re: Could a magnetic field around CIMs cause fuses to blow?
 

Voodoo diagnostics is a tricky business, but I think I have a theory that fits your facts.

I assume your software is controlling two motors with a "right side" pwm signal, and the other two with a "left side" pwm signal. If you have one left side motor being controlled properly but the other one controlled with the right side signal, they will oppose one another when you try to turn, and you will trip a breaker if you're lucky. Same with the right side, though it sounds like you've never gotten it upset enough to actually trip a breaker, instead just having a motor being backdriven against its will.

If you remove the fuse for the wrong-sided motor, that motor will be turned by the other one on the same gearbox, and you'll end up with the Victor getting powered by the generated current.

You can either 1) disconnect all your motors and watch the lights on the Victors as you go from neutral to full throttle to full turn, and see which ones respond; or 2) double-check the code, the pwm cables, and the motor wires to make sure they all agree.

Since you insist your wiring is correct, your software is at fault, but it'll probably be easier to correct the problem by changing which pwm outputs your Victors are plugged into.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

We removed the fuse for both moters on the one side. Somehow, the victors, suposedly disconnected from anthing when we removed the fuses, would still work when the other side, still connected, went. In testing the connections this morning, I saw that all of the reds were connected somewere. Looking at the wireing revieled that it looked OK. The wires arn't grounded to the frame or anything else. Black wires were connected to themselves but the Black and Red wires were isolated from each other and the frame.

Uh.. Should I be getting contentutiy through the breaker Panel with fuses out? I put one lead on the battery termainal and the other on a termainal for the moters. The resistance was great but I though it should be infinate.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

That could be explained if you've gotten confused about which Victor is connected to which motor. Pull all the circuit breakers, then put them back in one at a time and see which motors actually respond -- and in which direction. If my theory is correct, you'll be very surprised when you think you're telling the right side to move but the left side gear train runs.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

When we tried to run the right side as you say (I don't remember which side, but it was only one side) the correct side ran at first exactly as expected, but it was a third victor that was lighting up and trying to go that was causing problems.

We were testing the breaker panel becuase we think that that might be the problem. All of the positive outs on the panel were contenius with each other and the battery in. We tested the battery in and an out that was with a fuse and got 0 ohms. We then tested the battery in an an out that wasn't with fuse and got 500 Kilohoms. From testing older panels, I think that we should be getting infinate resistance because the breaker should be completing a circuit. If I am wrong, Please post fast because we don't want to have to buy a new panel. That would suck :(

Re: Could a magnetic field around CIMs cause fuses to blow?
 

If you are measuring resistance from each output of the breaker panel to battery common, 500k should be OK, 500 is not so be sure what you measure. If you leave all of the breakers in you will ready continuity from the output of each breaker to any other output. If you measure with all of the breakers removed they should be 500K or more. You should then go back and measure the outputs of all the speed controllers (both motor+ and -) to battery common and to the frame. There should be a high resistance to battery common for all terminals. When you measure all controllers outputs to frame they should be infinite.
The continuity test on a Fluke meter (the beep mode) should be sufficient for tests. If it beeps for any test that should be an open, you have a problem. A constant tone indicates a short, a single tone indicates a solid state junction af at least 0.3 volt drop, no tone indicates a resistance that results in a voltage drop greater than about 1.5 volts. What is really cool is the reading on the Fluke in "Diode test" is in voltage dropped across the device you are testing.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

If the breakers are pulled, you'll still be getting a little bit of circuit sneakage through the Victors themselves. Measuring from one point on the breaker panel will tell you the resistance through the first Victor to ground and then back from ground through the second Victor. A measured resistance of 500k wouldn't surprise me.

Have you pulled all the CIM fuses and put them back in one at a time yet? So far, your descriptions still seem consistent with having one of the left-side pwms controlling a right-side motor, and vice versa.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

We're not quite sure if it is 5000 ohms or 500k ohms. We have old multimeters. They do have a contenutiy test but it doesn't display units. They panel was removed and separated from everything and we were still getting odd numbers. The contenutiy test didn't beep (it beeps if there is a connection but not at every level) I wish we could test it better. When we checked with the regualar ohm meter setting, we were getting bouncing numbers between .05 and 10 in the 200K setting. How this works, I don't know. if 500k is OK, then I don't know what is wrong, we checked everything yet again for shorts. The only thing that seems to be wrong is the panel.

I already said this on This thread, but it bears repeating. We compared the panel to someone elses that works and found the same numbers. We arn't going to replace the panel yet, but that puts us back at square one.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

Bryan,
Where are you located? Are you going to be in front of the robot tonight? If yes, PM me and let's see if we can set something up.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

If for some reason Al cant help you out tonight, it seems your team is just outside of the Richmond, Va area. I would suggest contacting one of the close to 15 teams in Richmond or the other team in Highland Springs, Va to see if they can help you prior to ordering a new Breaker Panel.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

We don't know what happened, but we looked inside the panel to see what was up and saw nothing. Our neighboring team let us check their panel and there was the same numbers. We put our panel back on and the robot worked. I wish I knew what happened to fix it. But I am glad that we didn't have to buy another one.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

as you could tell from above comments it will cause problems. Metal shavings got into out victors and blew two out. i will say that from your pictures, you guys did a very neat job of wiring components.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

We took care to prevent metal shavings and the like, then took off the fans and used an air hose to blow them out for good measure. All of that before we turned them on for the first time on the robot (they were on but not attached to something for testing purposes earlier, but no metal near them).

Re: Could a magnetic field around CIMs cause fuses to blow?
 

That is good news. But Murphy's Law says this problem will come back and bite you if you don't get it figured out. Make sure you find the original problem so you know what the cause and fix will be in the future.

Re: Could a magnetic field around CIMs cause fuses to blow?
 

Thank everyone for all of their help on this matter... After going back and re-rechecking everything again, and making sure there were no shorts, and the frame is not grounded, and just throwing the (mabye) defective breaker panel back onto the bot, it performed wonderfully. We are hoping that the problem originated in the breaker panel (we ordred one yesterday on overnight shipping for $130) and when the ghost comes back, we will be ready...
Thanks again for everyone's help
Team 617