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Unipolar stepper motor driver problems....help needed

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kanishka13

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unipolar stepper driver schematic

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???:arrow::arrow:
 

l297 unipolar circuit

ULN2803 isn' designed for 1 A load, consulting the datasheet would help. Why don't you use 4 individual small MOSFET instead? Because of low saturation voltage, they are operating much cooler than a driver IC. Most MOSFET are able to absorb also inductive overvoltage. they won't need additional free-wheeling diodes.
 
uln stepper driver

It's ok for replace the driver circuit with L298-L297. Use only 4 terminals from motor and use circuit for full-step. You have a current limiter and the torque is high for bipolar motor. Change the supply with 30V / 2A non-stabilized, but good filtred (ex: 3300 - 4700 uF).
 

unipolar stepper driver

u can also try to join the o/p i.e tie 3 o/p of the uln and the corresponiding i/p together. now take o/p form the common o/p for a single coil of the motor and u have what u need!!!
 

+stepper +current +limiter

hi ,

i go thorough the data sheets. the uln is only rated for 500ma.as your hungry motor asking for 1.2A.i suggest to stack three uln top of each other and solder it . i used that method on one of my robo and it worked very well.that's the easiest solution if u have already made pubs.

or else i suggesting to use l297 as it rated for above 1.5A(not sure or must be 3A or 1.5A) for each bridge. ther 2 H-bridge on the ic so u can get 4 driving ccts using both bridges easily.the schematic can be found on the data sheet.

good luck

rg'ds
dilan
 

Re: unipolar stepper driver schematic

kanishka13 said:
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???:arrow::arrow:
Click to expand...
HELOOO.
i have the same atmega 32 mini pin 2 and i have the program in bascom and the plate for the stepper motor with uln can you send me your program for atmega ??? thank you
 

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