Unipolar stepper motor driver problems....need help

l298 unipolar

Hello friends..

I am using atmega32 to drive two unipolar stepper motors (5 wired) rated at 12V,~1A
I had been using ULN2803 to drive these stepper motors...
I face a strange problem....
1.The ULN gets heated very quickly.
2.I get varied results every time i power up the circuit

I am driving these motors with a 12V,1.2A power adapter..

I have damaged 4 ULN's already..

Every time I replace the circuit with a new ULN the circuit works fine initially...but later does not...

There is no whatsoever problem with the circuit...no Vcc-gnd shrt ciruit....

Could it be that ULN cannot sustain the 1.2A current??...so do i shift to another driver circuit?

What if I replace the driver circuit with L298-L297 motor driver circuit???

Mine is a unipolar 5 wire stepper motor with 12V supply....so what wud i driver circuiry be if i were to use l298-L297 driver circuit???ArrowArrow

l298 unipolar stepper

Did you read the ULN2803 datasheet?
Imax=0.5A

unipolar stepper driver

Hi
If you need speed then go for l297 l298 combination

else 4 mosfets is enough

Regards
Nandhu

l297 l298 unibipolar

Hi!
The ULN2803 is rated at a maximum of 500mA current per channel so it will definately heat up and burn out. Always read the data sheet carefully before using a device.
Instead of using the ULN2803 use darlington transistors like TIP120/121/122. The are very nice devices with built in protection diodes (inductive loads) for stepper motor driving.
The other solution is to use the unipolar motors in bipolar mode and use H-bridge driver IC's like L298,L6203 to drive the motor but that is a bit complicated.

Regards.

uln2803 stepper motor

I used TIP122 transistors once but I think IRL520 or similar MOSFETs would probably be a better choice.

Please note that Allegro has a rather large assortment of hybrid unipolar (and bipolar) stepper motor controllers.

Good luck with your project. Mike