Problems with Adafruit Motor Shield

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jasonashton
 
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Problems with Adafruit Motor Shield

Post by jasonashton »

I'm currently trying to control two 1.2 amp drill motors with this shield. Everything was working great until recently. It appears there is something wrong with the motor driver chip that controls m1 and m2.
Both chips have been heatsink'd since the beginning and I don't think it over heated. The way I diagnosed this was I made sure I could run both motors off of m4 and m3, they work fine. Yet neither motor will work on the other side, with the same exact code. Could there be any explanation or fix for this? Or is the shield broken... Thanks

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adafruit_support_mike
 
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Re: Problems with Adafruit Motor Shield

Post by adafruit_support_mike »

Which version of the motor shield are you using, v1 or v2?

jasonashton
 
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Re: Problems with Adafruit Motor Shield

Post by jasonashton »

Its version 2. I received it a week ago

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adafruit_support_bill
 
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Re: Problems with Adafruit Motor Shield

Post by adafruit_support_bill »

What power supply are you using for the motors?
Do you have a spec sheet for these motors?

jasonashton
 
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Re: Problems with Adafruit Motor Shield

Post by jasonashton »

I am using the 18v battery that comes with these drills, put through a 12v regulator, so the board gets the appropriate 12v. I do not have a spec sheet as they came out of the Harbor Freight drills. I believe they are 1.2 amps max. The motor shield was previously working fine on all four ports.

We always made sure to keep the motors on opposite drivers since they have the max of 1.2 amps. At one point we had both motors running fine. However, the last few days the m1 and m2 driver doesn't appear to be working correctly. The motor will either pulse, turning on and off, or on the m2 port it just quickly slows down and stalls. This doesn't happen on the other side.

jasonashton
 
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Re: Problems with Adafruit Motor Shield

Post by jasonashton »

Another update - I just tried all four ports again. The motors only seem to work on m4. All the others have issues it seems, which leads me to think it isn't the motor drivers.. I don't know what it could be now

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adafruit_support_bill
 
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Re: Problems with Adafruit Motor Shield

Post by adafruit_support_bill »

All the cordless drill motors I have experimented with drew 20 Amps or more. Reducing the voltage by 1/3 will reduce the current as well, but it is probably still well over the 1.2A rating for the chip. From the symptoms you describe, It sounds like the driver chips are burning out.

These do have thermal shutdown circuits to protect against overloads, but with repeated overload conditions damage will accrue over time.

jasonashton
 
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Re: Problems with Adafruit Motor Shield

Post by jasonashton »

I just remeasured the current and it only peaks at 1.1 - 1.2 amps. These are very small and low power motors, not anything like the huge Dewalt motors or anything like that. I ran the motors on m4 for awhile today (10 mins?) and the heatsinked chip was only slightly warm to the touch.
Ports m1 and m2 haven't worked right from the beginning. The pulsing has been a problem on m1, but m2 seemed to work until a couple days ago.

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adafruit_support_bill
 
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Re: Problems with Adafruit Motor Shield

Post by adafruit_support_bill »

What is the resistance across the motor terminals?

jasonashton
 
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Re: Problems with Adafruit Motor Shield

Post by jasonashton »

I can't test that right now, I don't have my multimeter at the moment. Just wondering, what would that tell you?

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adafruit_support_bill
 
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Re: Problems with Adafruit Motor Shield

Post by adafruit_support_bill »

In the absence of a spec sheet, it gives me a rough idea of the motor characteristics.

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