Motor Shield Limitations? Overheating?

The more I play with things, the more I think I am seeing this happen somewhat frequently. I think it always happens while the zaxis is attached.

Attached is a gcode file for a simple 5.5 inch square with three depth cuts. If I run this file with the top edge of the square an inch or two below the top of the work surface centered horizontally in the work surface, I get some choppyness mostly on the second and sometimes the third pass of the top edge. I think this occurs because the zaxis remains attached during the entire length of the top edge.

If anyone else is able to test this I would appreciate hearing your findings. You don’t need to actually cut anything, but having the weight of the router in the sled is probably helpful.

Square 5.5 Forum.nc (1.6 KB)

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check the routing of your wires (and that everthing is plugged in well), if you
have too much noise being picked up in the encoder wiring, it can make the
maslow think things are moving when they aren’t

I’ve run your Square 5.5 Forum.nc with release 0.92 and the ‘Enable 3D Linear Movements’ branch and did not see the choppy behavior you mentioned. There were some times when the horizontal movement paused waitinfg for the z-axis change to complete, but I don’t think that’s what you’re describing. It seems OK on my setup with GC0.92

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Awesome, thank you. Maybe I am just being over cautious.

There is a 12volt connection on the maslow board, what about adding a 120mm fan? How much wattage would it be safe to suck off that connection?

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I have an 80mm case fan mounted to my electronics enclosure, at the very least it keeps the heat sinks very cool. I haven’t really pushed my machine yet, however, so I don’t know how well it will cool the electronics when the sled is in one of the high-stress locations on the bed. I have documented my fan mount here: Arduino/Motor Shield Enclosure (Picture Heavy)

Not sure how much power the board can take but as an alternative, I just crimped the fan to a 12v power supply and plugged it into the same power strip that runs the electronics. That way the fan turns on with the machine and it doesn’t take any power from the motor shield.

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I’d bet there’s enough extra capacity on the 12volt supply to run a fan. The power supplies we used have a built in resettable over current trigger not a fuse that needs to be replaced so if you do end up drawing too much power it should be ok. If I remember right if the power supply goes over current it will shut down and the status LED will blink until it is turned off and back on again

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When you purchase the Motor Controller in the Store are the heat sinks included?

Yes they are. They come with double sided thermal conductive tape.

@Gero - I’ve been thinking of getting a spare set of electronics. If I had the chops I’d use my Shapeoko 3 to make an Aluminum case for it all, one giant heat sink.

@bar - Would you consider updating the store picture to include the heat sinks?

Thanks everyone :slight_smile:

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In a previous life I used to QC processor chips to destruction.

One thing we learned was that lapping the chip and heatsink has a measurable effect on its ability to transfer heat.

As the chips are pretty flat to begin with, we first flattened the sinks using 320-grit wet and dry on a sheet of glass with 3-in-1 or sewing machine oil. Once they were done you could use the resulting grit paste to give the chips a few turns using the sink as the block.

Clean down well using an appropriate solvent (iso, vodka), then gently wash in warm water with a drop or two of dishwash - you need to ensure no aluminium dust is left behind - dry well (a can of Air helps, and a day on top of the water heater to be sure) and mount the sink using a quality thermal paste - I prefer a silver conductive paste, but you need to be careful you don’t cause a short. If you’re worried, use a non conductive paste.

Another advantage of lapping is that you will only need a tiny amount of paste.

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Yes! Thanks for letting me know that is unclear. I will add a picture with the heatsinks to the page

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Just an update on this.

I am relatively confident that I damaged one of the motor controllers on the v1.1 heat shield. I don’t think this happened in normal use, but instead I suspect it happened when I tried to increase the controller frequency.

I think I have seen the issue for quite some time, but it was very apparent when I was testing different PID values, one of the motors acted extremely differently than the other. Annoyingly the problem in my case manifested itself as an oscillation in the movement which could easily be confused for other errors.

I suspect that the motor controller somehow became more sluggish. That the PWM output from the arduino was slower to cause a voltage change on the motor side. If I was a more advanced electrician I could probably confirm this, but I don’t even own an oscilloscope.

Just a data point for people to consider in the future.

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The motor shield was designed to be running at the edge of it’s capabilities to
keep the price down.

I think it would be a good idea for future versions to have a little more
headroom. too many people have been damaging their shields

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I’ve run into this too.
I’ve been looking at a different driver chip, the TLE5206, which offers over-temperature protection and a thru-hole package that accommodates bigger heat sinks.
The software will need to change, though. The present approach is to set the direction with two output signals and the speed with a third PWM signal. The TLE5206 wants two PWM signals and chooses direction based on which one is active and the state of the other one.

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I’m working on a case with an active cooling tower for each chip.

I need to wait for the fans to come back in stock. Please let me know if these are of interest to you.

Thank you

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those 3d printed cooling towers are cool. can you share stl please?
I know I am replying 8 months late! sorry.

What type of printer are you using?

I didn’t put the files out because it is a very difficult design to print. I’d say 1 out of 10 prints might be successful.

I’ve PM’d you on this also.

Thank you

cr-10, now that I look at the design yes it does look hard to make without supports

Maybe I will split it in two and just glue the two halves together.

Hello. Since my board with tle5206 seems dead I am fiddling with some spare hbriges I have. My hbridge like tle5206 have two pins per motor, but with tle5206 settings in motor.cpp is not working. On my hbridge first pin chooses direction LOW/HIGH and second pin is used as PWM. I tried so many combinations but non of them is working. At best I had Left motor spining both directions and Right motor only one in test motor encoder but that was succesful 1 of 3 tests and with changed pin1<->pin2. Can somebody point me in a right direction?