Smart Motors have no power

Hi, I have searched the forums and I haven’t seen where anyone has explained a fix for my problem. I have about 10 smart motors that have completely stopped working. There is no red light at all. We have tried different ports and different smart cables, but there is no power coming to it. The only thing I have found is to contact customer support. They emailed me and said that if it is out of warranty (which I assume as I purchased most of them 3 years ago) it would cost $60 per unit (more expensive than just purchasing new motors), and I could only send in 5 per school per year.

Has anyone else had this problem, and is there anything I can do to get these motors working again?

Thanks!

At that point, you should open them up and check the gears and leads. Something may have unsoldered itself, or the gears may have stripped.

Does the brain get power? Because that might be the main problem.

Yes, the brain has power. I tested the same port and smart cable with a different motor that worked, and everything else worked.

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How many motors do you have plugged in at a time?

Okay. I will do that and see if that is the problem. Thanks!

Just one as I am testing them.

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if the light on the motor doesn’t even turn on, and you’ve made certain it isn’t any of your other electronics causing the issues (brain, cable, battery) than sadly your motors might just be dead.

do you get a lot of static electricity on your field? in the past my team has experienced motors and brain ports getting completely fried from static electricity. This problem was very severe, but it was completely solved when we got some of the anti-static field tiles.

the issue could also possibly be faulty cables or brain ports that do something to break the motors. I haven’t experienced this or heard of it happening, so this is just speculation but it’s not outside the realm of plausibility.

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Thanks. That’s what I am afraid of. This year I did spray my field down with anti static spray, so hopefully this doesn’t keep occurring.

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if you have a static problem you will probably be able to tell. before my team fixed it, we took up the habit of resting our feet on the field perimeter while working so that we couldn’t build up a charge and get shocked on the wall. it was extremely frequent and the shocks were actually quite painful.

if you’re actually getting static shocks frequently on your field, than there is definitely enough static to fry some ports.

In my experience with static, usually static does not kill the motor in its entirety. Usually a motor or brain port that is fried from static electricity is usually fully working with the exception of a chip called a RS-485 transceiver. This is the chip that serves as the data link for the smart ports. The death of this chip usually doesn’t break the power handling, and the motor light will blink as a result. I have a friend who made an excellent guide on what happened and showed how he fixed the damaged ports on a brain.

Now on to your problem. This doesn’t sound like static electricity. As a quick verification, plug in a known good motor in with a cable and make sure you can spin it. After that, take the motor off the cable and place your bad motor on. What does the motor light do? If there is no light, it sounds like a power regulator is dead or something further in the motor is damaged and there is no fix. If a component that has code is damaged, it is basically unrepairable. These damaged motors could be parts motors.

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Okay. Thanks for the help! I think that was probably our problem.

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This is super helpful! Thank you so much for sharing! I just wanted to know for sure before I moved on from them. You are probably right, these motors will probably have to be parts motors for now on. Do you know what could possibly cause this problem, and if I can prevent it in someway?

Unfortunately I do, and its partially the fault of vex. These chips are fairly sensitive to static electricity, which is generated in abundance by moving parts. Plastic on plastic rubbing(balls,cubes,rollers) have the worst habit of generating it. That static can travel through the wires and into the brain or motor ports. In our teams experience, the brain often recieves the jolt. This damages the RS-485 chip.

What’s bad is that there is a possible fix to the problem. A few diodes and resistors per port could greatly reduce the frequency of the issue, but they are not in either side of the smart port as vex did not include them. Since it is not competition legal, our club has not tried to discover how effective this solution really is.

In order to reduce the issues there are a couple of things to try. Static spray is a must. You could try to make sure moving parts are connected with metal(no completely disconnected metal parts), and make sure the motors do not directly contact game pieces.

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First off, I would recommend that you inspect the pins on the connector. Having no light at all on a motor is much rarer than the typical short blink from a static shock. The pins can be bent down easily by an improperly crimped cable causing the motor to stop working. A paper clip with a small bend at the end should be able to bend the pins back up.

If that is not the issue, you can swap the internal motor (which can be easily unplugged from the board) to another motor that had locked up to get one working motor between the two.

Additionally, I have been using 5mm ferrite cores clipped around the cables near the brain end and they are very effective at preventing ESD from damaging both the brain and motors. They are in a legal gray area, but could be considered commercially available wire protection. We have never been called in it, but if you are they can be easily unclipped in a matter of seconds so even just for practice they are worth getting.

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Two questions about the ferrite cores. First, how effective have these been? Would it be worth it for a club to invest in them? Second, have you or anyone else asked that question on robotevents? I love the idea of a set-and-forget kind of ESD protection. Our club has been thinking of making a test PCB with the RS485 protection circuit for testing, but we haven’t had much time to develop that test.

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somesort of set and forget ferrite cable cover would be cool
and then you could add colors to it for swag

Very. I started using 9mm ferrite cores (with the cable making several loops through) in TP. We had lost at least 5 ports from our lift motors. I have only ever seen a port die once and the static on that field was several times worse than the worst I had seen before (just taking two steps on the field and then touching the wall caused noticeable pain). This season we switched to 5mm cores because they were more compact and have not lost a single port after (we did kill a port or two before we added them to this robot). You can buy 12 5mm cores on amazon for $7.86.

There has not yet been an official Q&A on it yet, but again it is easy to remove at a tournament with no effect on match outcome if needed.

I started using them after I ran an experiment using a V5 cable to discharge my own body static to ground. Every time I tested with a normal cable, I would feel a strong shock and discharge completely (when I would touch ground directly afterward there would be no shock). When I tested with a cable with a ferrite core, I wouldn’t feel any shock, but my static was still completely discharged.

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Thank you! I will check those pins! As for the ferrite cores, do these just help discharge the extra static? Could you send a pic of where you put them on the cables? Thank you!

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The idea behind the ferrite bead/core is to suppress the large voltage spike caused by the static. Static electricity damages devices buy suddenly surging the voltage through a conductor(some static discharges can exceed 20,000 volts!) This ferrite bead in theory works by converting the static discharge into heat. They can’t eliminate the problem, but they may reduce it. I’m extremely tempted to try it later.

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