CPX boards overheating with servos

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KathyCeceri
 
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CPX boards overheating with servos

Post by KathyCeceri »

I already mentioned this to PT, but for the record: I taught a class today over Zoom with families who are using their Circuit Playground Express boards and their servos for the first time. Four of them had their boards overheating. I've taught this class many times, so I don't think it's the set-up or the MakeCode program we used.

I've had boards overheat before, but not right out of the box. Usually after they've been used by a lot of students. After looking at earlier threads with this issue, I've been telling my students to keep the servos at 90 when not moving, to limit the movement between 10 and 170, and to add a 1000 ms pause after each movement.

Several of the students will be starting another 5-week session of CPX robots next week, so I hope there's a way to fix this. Thank you!

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KathyCeceri
 
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Re: CPX boards overheating with servos

Post by KathyCeceri »

FYI, here's where I found the issue in 2019. Hasn't been a problem between then and now! viewtopic.php?f=58&t=156907

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adafruit_support_carter
 
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Re: CPX boards overheating with servos

Post by adafruit_support_carter »

Four of them had their boards overheating.
Is this anything you've been able to recreate locally?

Was it clear that no unintentional shorting or incorrect pin connections occurred?

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KathyCeceri
 
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Re: CPX boards overheating with servos

Post by KathyCeceri »

MakeCode Servo example.jpg
MakeCode Servo example.jpg (74.05 KiB) Viewed 181 times
Here's the MakeCode program we built in class: https://makecode.com/_hRwEq8195Ead

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KathyCeceri
 
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Re: CPX boards overheating with servos

Post by KathyCeceri »

I had a board overheat recently, but I have no idea how old it was, or if it was one I used with students in the past. The boards the kids used today were all right out of the box, purchased by their parents in the last few weeks.

I did have them hold their boards up to the camera to show me how they attached the wires, as well as when they plugged the servo cables into the alligator clip/male header pin wires.

The servos were working before they got hot.

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adafruit_support_bill
 
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Re: CPX boards overheating with servos

Post by adafruit_support_bill »

Do you know which component(s) on the board were overheating?
What model servos were being used and how was everything being powered?

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adafruit2
 
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Re: CPX boards overheating with servos

Post by adafruit2 »

it could be the servos got 'pinned', were held or moved, or were connected backwards momentarily. servos are a bit challenging because they can draw an amp. connecting to 3.3V might reduce the voltage but the current could still be pretty high. that said, if you're drawing an amp...the board is going to get hot!

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KathyCeceri
 
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Re: CPX boards overheating with servos

Post by KathyCeceri »

As far as I know, everyone bought their parts from my Adafruit wishlist, which means they were using this micro servo: https://www.adafruit.com/product/169 They were all using the boards while they were plugged into their computers, via the USB cable that comes with the CPX Base Kit.

I don't know where they kids' boards were getting hot ... when I've had that happen, it was in the vicinity of the speaker. I recall reading somewhere that there's a chip next to the speaker that could be the cause. Apparently, I also put a warning about the speaker getting hot in one of the Learning Guides I wrote. (https://learn.adafruit.com/cpx-musical- ... code-music)

I doubt they *all* connected the wires backwards. I always show them a photo like this from another of my Learning Guides (https://learn.adafruit.com/assets/63955). The parents are usually standing by offscreen to help.

So: I can have them connecting to the 3.3V. Not sure what else to try.

Question: Are the boards still safe to use? Or do they need to be replaced?

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adafruit2
 
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Re: CPX boards overheating with servos

Post by adafruit2 »

if they enumerate on USB they should be fine. there's a fuse and some thermal protection on the LDO. the fuse could also be the thing that overheated (its to protect the rest of the board!)
i'd make sure they arent using A0 for sure, and power from 3V as a try

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KathyCeceri
 
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Re: CPX boards overheating with servos

Post by KathyCeceri »

CPX+clips.jpg
CPX+clips.jpg (155.47 KiB) Viewed 138 times
Thanks for your reply. Some additional questions - I want to be sure I understand all the terms you're using:
if they enumerate on USB they should be fine.
-- Does "enumerate" mean running everything off the USB power from the computer? Can they use the battery packs (3 X AAA batteries) as well?
There's a fuse and some thermal protection on the LDO. the fuse could also be the thing that overheated (its to protect the rest of the board!)
-- Can you just give me a quick explanation of what LDO is and what you mean by thermal protection, so I can explain to the families?
i'd make sure they arent using A0 for sure
-- Do you mean the A0 pin on the board? I will double check. (Image I showed them is attached.)
power from 3V as a try
-- I will, thanks!

Also:

Would using 9g microservos other than Tower Pro brand from Adafruit be an issue? I believe the parents all bought from Adafruit, but I have told people beforfe that they could buy offbrand elsewhere in a pinch.

Would you like me to send you a board of mine that overheated to check out? If so, tell me where to ship it. (I'll throw in an Adafruit micro servo that quit working too.)

Thank you!

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adafruit2
 
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Re: CPX boards overheating with servos

Post by adafruit2 »

enumerate means that if they plug it into USB to upload code it appears as a disk drive when they double click (the bootloader launches) - if htat happens it pretty much means everything is OK because the chip is fine

LDO is the power supply, it has protection against overheating and will shut down if it gets too hot.

any microservo is probably OK but make sure its plastic gear NOT metal gear and is a true microservo and not a larger servo. also have them show you the alligator to servo connections in case they got those wrong

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