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Unread 05-05-2009, 07:47
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Al Skierkiewicz Al Skierkiewicz is offline
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Re: Review of a small motor controller schematic.

Austin,
First thing to add is the protection diodes across the motor leads as shown in the TI specsheet. These are normally a part of the power FETs in our current controllers so with the L293D they have to be added externally. Insure that the diodes are placed on the board such that large motor currents do not inject noise into the power supplies. Normally this is done with separate return traces just for the diodes and motors tied back to power input. Also keep in mind the maximum current specs of 1 amp when you choose your motors. Also check the requirements for the bypass caps on the LM1117. High output capacitance near the chip might be detrimental. The spec sheet shows a 22mmf. Something larger may cause current foldback when starting.
Let us know how it works.
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Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
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Storming the Tower since 1996.