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Topic: IC "L293B" always outputs 0.5 V (Read 1 time) previous topic - next topic


Jun 17, 2012, 03:55 pm Last Edit: Oct 02, 2012, 09:27 am by DevilsChild Reason: 1

I'm using an L293B to drive motors. As an Input I'm using an arduino pin and the output is constantly on approximentaly 0.5V.

This is how I connected it (IGNORE the left side!)


On the left side, I connected the wires to the input instead of the output for testing purposes. On the right side I connected the 3 wires to the output, but for some reason it is always 0.5V.

Any ideas?



I followed these instructions (image included)



I mean your shematic in how your wiring it,
that gives a bunch of examples, what are you trying to power?


By schematic you must mean the screenshot in the OP. As for the code: I'm controlling floppy drives and this works without a driver up to 20 drives. For more, I need a driver, but then it doesn't work at all. The input is a sound signal and the output is constant 0.5V, but I don't understand why.


Yeah sorry, got lost following those wires around, usually there's a written plan on paper or something
Your not applying the sound signal to the input right? Its for either a logic high or low input not a varying ac signal
the output is digital in a sense, each part of the hbridge is fully on or off not amplifying
I don't know how the floppy drives work with an ac signal but maybe im getting the wrong idea somewhere,
if you want to amplify an analog signal then maybe you could look into using a transistors or mosfets in the linear region to amplify the ac



the with instructions is this one: http://xload.dev-ch.com/37bc8724fecfd8f5/l293b.pdf

And I'm not using an analog audio signal. Instead I'm using a 50% duty cycle digital signal for the input and expect the same for the output only with higher current.

Btw: On the right side, the 3 wires are not connected to the IC output but to the arduino pins directly, which works. But once I connect them to the IC output, it doesn't work.


What are you controlling on those floppy drives and why?

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That link is to the datasheet for the l293b, not really instructions


You have pin 8 connected to ground.  pin 8 is the motor positive supply.
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Yea that could garuntee it not working


You're damn right there :D
I finally got it working by attaching pin 8 to 5V of the PSU.

Thank you!

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