problem with stepper drivers uln2803

I am using two stepper motors for my micromouse..
To drive two steppers can i use only 1 uln2803..



please help me understand the difference between the two circuits above..

my stepper specification is 500mA,6-12V..

so for my specification which of the above two circuits is better??

How to select the value of zeners to be used for my stepper specification??

please help..

Why are you using Zeners? Just tie the clamp (pin10) to +24

Neither!

You can NOT run your 12V stepper from 24V!

You can NOT connect the clamp diode! ( the two windings are on the same iron, and you will be shorting out the windings since each winding pair acts like an auto transformer )

Your switches need to be able to have more than double the breakdown voltage of the supply.

Dan

Ahh I missed the 12v stepper on a 24v supply. Although it's common practice to run steppers at higher than rated voltage if you're careful.