l293d problems with 89c2051 microcontroller

[darkolee]

I am currently building my first real microcontroller project. I am trying to drive a stepper motor!
I am using ATMEL at89c2051 to try to drive an h546 stepper motor (datasheet active-robots.com/products/motorsandwheels/stepper-motors/datasheets/103h546-0440.pdf )

I am using an l293d with inputs connected from pins p2 and p5 of the microcontroller. Now I have a couple of questions. Since I am using a unipolar stepper motor is there any other motor driver other than the l293d (which is an h-bridge and usually used for bipolar) which is more siutable for me? On the net everyone suggests using ULN2003 or so but my motor is rated 1A so i think I can't use this chip, can I?

One problem I am encountering is that for some reason whilst the motor is turning, some pins on the microcontroller turn high - even when these are unconnected! I am suspecting that the problem might be because I am not using any protection diodes at all (and the back emf some how freaks the microcontroller -excuse my terminology . Could this be the problem? If so where should I connect these diodes and what ratings should these have? - Aren't these diodes included in the l293d itself? Or could this problem solely be because the microcontroller is faulty?

Finally please keep in mind that I am a total beginner and newbie in the area so please excuse my ignorance :S

thanks in advance
darren

 

[elfcurry]

L293D vs ULN2003

Please treat this as a provisional response Darren. I'm interested in people's answers to this too as I'm likely to be doing the same fairly soon.

I'd say that if you're able to provide the detailed control sequences in software, then using a L293D sounds good to me. With an H-bridge you can choose to pass current through a coil in either direction which is necessary for stepper control, but I don't think this is possible with a 2003 as they are meant to switch the low-side of a circuit (coil, lamp etc) assuming the other end is connected to the supply. I hope I got this right.

There is a current limit on a 2003 is 500mA but you can connect several inputs and outputs together to overcome the limitation so you could drive a 800mA solenoid this way.

 

[ericgibbs]

If so where should I connect these diodes and what ratings should these have? - Aren't these diodes included in the l293d itself? Or could this problem solely be because the microcontroller is faulty?

hi,
The application notes in the L293 datasheet explains how to fit diodes across the motors.
Do you have the L293 datasheet.?

The L293D has internal diodes.

 

[asaini88]

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