DC Motor 1 only goes backward, 2 has small drift

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Schmigneous
 
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DC Motor 1 only goes backward, 2 has small drift

Post by Schmigneous »

I've assembled my motor shield and I'm testing it with my DC gearmotors. When connected to M1 the motor only responds to the BACKWARD command. When connected to M2 the motor goes both directions but has a constant ~20 RPM backward spin when it's supposed to be stopped. I've tested it with 3 different motors and the response is the same.

Besides the standard configuration, I've swapped out the L293D chip in favor of 2 piggybacked SN754410 chips plus a heatsink. Also, I damaged the C4 capacitor when assembling the shield and replaced it with a .1uf ceramic disc capacitor. I assumed it was the same thing. There also might be an issue with the connection on the C1 capacitor. Would any of those issues explain my symptoms?

Thanks.

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adafruit_support_bill
 
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Re: DC Motor 1 only goes backward, 2 has small drift

Post by adafruit_support_bill »

Post photos of the front & back of the board & we will have a look. Does the shield behave differently with the original L293D's installed?

Schmigneous
 
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Re: DC Motor 1 only goes backward, 2 has small drift

Post by Schmigneous »

Here is the shield I assembled. I'm not the greatest solderer.

Image

I'm not able to try the L293D in 1C1 because I soldered the SN754410s in there directly, because I thought the piggybacked chips wouldn't fit in the socket, and because I'm an idiot.

I had tried the motor from the Experimentation Kit in M1 and M2 and got the same weird results I described above, but when I put the same motor in M3 or M4 it worked fine. I'm unable to try my gearmotors in M3 or M4 because they draw too much current for the L293D.

As suppose if nothing else I could try unsoldering the SN754410 stack and putting it in the 1C2' socket.

Anyway, thanks for checking this out, and let me know what you think.

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adafruit_support_bill
 
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Re: DC Motor 1 only goes backward, 2 has small drift

Post by adafruit_support_bill »

A little more solder than necessary on some of those joints, but otherwise fairly clean. It sounds like there may be a problem with how you piggybacked the SN754410s. Do you have both chips with the notch on the same end?

Schmigneous
 
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Re: DC Motor 1 only goes backward, 2 has small drift

Post by Schmigneous »

I double-checked the chips and they're both aligned properly, notches toward the "top".

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adafruit_support_bill
 
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Re: DC Motor 1 only goes backward, 2 has small drift

Post by adafruit_support_bill »

Can't see much in the photo. But check over the soldering on your piggy-backed chips. Make sure all the joints look good with no shorts between pins.

Schmigneous
 
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Re: DC Motor 1 only goes backward, 2 has small drift

Post by Schmigneous »

I had a little trouble unsoldering my chips. I think I'm going to try a different motor driver. Nobody's fault but mine.

Image

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adafruit_support_bill
 
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Re: DC Motor 1 only goes backward, 2 has small drift

Post by adafruit_support_bill »

:shock: Well, I don't think there is much to salvage from that chip :!: . At this point, removal will be much easier if you clip all the remaining legs and de-solder them individually.

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