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Arduino Duemilanove with Adafruit motor shield causes piggybacked motor drivers to overheat- even with no load. Ideas? Answered

I have an Arduino Duemilanove and an Adafruit motorshield. Both work fine, but the motors I want to run require more current than the available 0.6 amps. I tried piggybacking two more drivers on top of the existing ones, but now when I turn it on one set of chips overheats immediately. It's not a soldering error, because I've tried it with many different chip configurations and the same problem occurs. The only thing I've noticed is that the new drivers I purchased have slightly different numbers under the customary L293D- but isn't that just when and where it was made? Any ideas?

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steveastroukBest Answer (author)2011-09-10

Just try a series resistor from EACH driver to the load and see what happens. No guarantees. Paralleling, unless these things are specifically designed for it isn't likely to work.

Steve

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loki17 (author)steveastrouk2011-09-11

Good idea...I'll try it. Oh, and the instructions on ladyada's website say that chips CAN be piggybacked to increase the potential current.

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steveastrouk (author)loki172011-09-11

Yes, well, what LadyAda says ain't always right. The 293 is a bipolar design: Bipolar transistors don't current share unless forced. Sure, it might work, but then, as you've found, it might not.....

Steve

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loki17 (author)steveastrouk2011-09-13

Ok, I still can't get it to work, so I guess I'll have to order some SN754410 drivers. But thanks for your advice. I appreciate it!

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steveastrouk (author)loki172011-09-13

Out of interest, did you get chips with in-built diodes, or did you put external ones in ?????

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loki17 (author)steveastrouk2011-09-13