overheat with inchworm robot

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Nivek
 
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overheat with inchworm robot

Post by Nivek »

Hello, we were doing the wiring and coding portion of the inchworm robot demo as a first servo project. We used a SG92R micro servo with the ATSAMD21developer edition circuit playground express that we received a couple weeks ago as part of the 2769 educators pack. We ended up wiring as described but using a different ground pin(pad) from what can be observed in the picture. So we had Vout, A1 and then the ground next to the A7 pad. We deployed the example make code for the project. After the initial start behavior we picked it up to press the a button. The board was exceedingly hot(definite safety issue) on the board side in the area of the speaker. We immediately removed power and verified the code and wiring to the description. The behavior repeated after reset and redeploying. It appears to occur when the servo is in steady state but did not test extensively. I had not used this board prior so i switched to a different board that we had used to see if it was board specific. It became obvious that the thermal issue was presenting on that board as well and we rapidly removed power prior to runaway(hopefully). Later i reviewed the instructions again individually and connected as implied in the photo with the ground proximal to the a1 pad, this behaved as expected on both boards without thermal issues with the exception that sound on the first board did not work. A direct test of only the speaker fails on the first board (sound was heard on the inital run). What is the guidance on selecting ground pads? Would an external ground buss be advisable? Is the damaged board still safe to use degraded or should it be replaced?

We have otherwise been thoroughly enjoying the product and content and have a new box of adafruit gadgets coming in today.
Thank you, Kevin

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adafruit_support_bill
 
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Re: overheat with inchworm robot

Post by adafruit_support_bill »

All ground pads are connected to the same ground-plane on the board. It should not matter which one you use.

Please post some photos showing your build and connections.

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Nivek
 
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Re: overheat with inchworm robot

Post by Nivek »

20220901_cpx.jpg
20220901_cpx.jpg (114.74 KiB) Viewed 216 times
There are 2 links to the make code that appear to have different targets, the one i was using is makecode.com/_9PfVyeYWMYz1 from the instruction page https://learn.adafruit.com/Cardboard-Ro ... n-makecode the other make code link does not play a sound. In recreating today for the picture the temp only increases after the button is pressed and the sound is played. This might be a live copy of the code as I believe it was different yesterday and a sound was played elsewhere as well. There is also an unattached set loud sound threshold block suggesting it may not be the correct version of record.

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adafruit_support_bill
 
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Re: overheat with inchworm robot

Post by adafruit_support_bill »

When you press the button, does the servo move as well?

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Nivek
 
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Re: overheat with inchworm robot

Post by Nivek »

Yes, the servo moves on the loud and button triggers

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adafruit_support_bill
 
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Re: overheat with inchworm robot

Post by adafruit_support_bill »

And with the servo disconnected, it does not get hot?

Even small servos can pull substantial current under load. But it looks like you have not attached the servo to your robot yet.

Can you identify a specific component on the board that is producing the heat?

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Nivek
 
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Re: overheat with inchworm robot

Post by Nivek »

Excellent question, I could not reproduce without the servo attached. I Had a second of the same model servo, it produces the same behavior. This time it did not seem to relate to speaker output but happened when the servo motion stopped after it was triggered from noise, this does not produce a sound. Sorry for the circular debugging, it is very peculiar.
It seems to be the FPA1C adjacent to the speaker, that is consistent with the traces where i feel heat on the back and i 'digitally' verified on the component side though my fingers are suboptimal.

All behavior has been with no mass beyond the horn attached to the servo and perhaps lifting itself from the table.

Thank you very much by the way

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Nivek
 
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Re: overheat with inchworm robot

Post by Nivek »

20220901_fpa1c.jpg
20220901_fpa1c.jpg (224.01 KiB) Viewed 199 times
I didn't find the part number off hand in a search so its the top left IC in the picture attached just in case.

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adafruit_support_bill
 
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Re: overheat with inchworm robot

Post by adafruit_support_bill »

Interesting. That part is the amplifier chip for the speaker. https://www.diodes.com/assets/Datasheet ... AM8301.pdf
It is not clear how that might be related to the servo.

If you remove the sound blocks from the code, does it still get hot?

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Nivek
 
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Re: overheat with inchworm robot

Post by Nivek »

I removed the play sound siren and the temp still spiked, then the set volume and it still spiked. I then removed the detached set sound threshold and it stopped; however, now the speakers do not work on either device and I cannot recreate the temp spike even reverting to the original code.

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adafruit_support_bill
 
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Re: overheat with inchworm robot

Post by adafruit_support_bill »

Sounds like maybe the amp chip is toasted. If it were just one board, I'd suspect a bad chip. The fact that you are seeing the same thing on two boards with a fairly simple program is puzzling. I'm going to check with the rest of the engineering team to see if anyone has seen anything like this before.

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argonblue
 
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Re: overheat with inchworm robot

Post by argonblue »

I wonder if electrical noise from the servo's power lines is coupling to the audio amp chip in a way that sets off a destructive high-power oscillation.

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adafruit2
 
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Re: overheat with inchworm robot

Post by adafruit2 »

i wonder if makecode isnt disabling the speaker by default
Nivek - please try connecting the A0 pad to a GND pad with alligator clip, does that help?

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johnpark
 
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Re: overheat with inchworm robot

Post by johnpark »

I have the program (version with sound) running on a Circuit Playground Express, with SG92R micro servo wired as shown in the guide and there are no thermal issues when I press either button or clap to initiate servo motion. Sound is working fine.

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Nivek
 
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Re: overheat with inchworm robot

Post by Nivek »

sorry for the delay, I connected A0 to ground. I do not get the overheat but i also do not get sound, doing a sound only program also fails to produce sound so i am presuming that both of my CPE boards now have the speaker amp fried. Should the boards be safe to use otherwise? All we have done was the sound level necklace example and what was documented in this thread.

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