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ULN2803 Stepper motor

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niranjan23

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Hello!
I have problem with my stepper motor and ULN2803.
I interfaced Bipolar stepper motor through ULN2803 to PIC18F4550, I made code to run motor Clock wise It works on Simulation but not on Hardware!
Im using 12V 4 wire bipolar motor .
Im using this circuit .
interfacing-stepper-motor-to-microcontroller.jpg
Also I tested Unipolar motor on same hardware!! didnt work!!.
when I checked voltage using DMM at pin num 9 and 10 of ULN2803 I get 12V but when I checked voltage at output pins I get 2.3-2.5V and when I run sequence the voltage at output pin changes like 0 to 2.5v to 0v until sequence ends!! But my stepper motor doesn't rotate.. Why and how this is happning what is the problem Help me:-:)-:)-:)|:|!!
Thanks!!!
 

The schematic makes no sense for a bipolar motor, it has no terminals 5/6. It must be driven by a bridge circuit and can't work with open collector drivers like ULN2803.

Unipolar motors work well with ULN2803 and the shown connection scheme.
 

Thanks for your reply...
I tried unipolar motor also but didnt work....your saying unipolar motor works well!! \but its not !!!! with uln2803
 

Hi,

Unipolar motors work well with ULN2803 and the shown connection scheme.

Unipolar stepper motors cause a problem, if the ULN has internal clamping diodes.
Because of the bifilar winding configuration, you may expect twice the supply voltage at the "non activated" wire.

Disconnecting the ULN's COM from supply voltage may help.
If you still want an overvoltage protection, then connect a zener with at least twice the supply voltage at COM (and GND).

Klaus
 
Unipolar stepper motors cause a problem, if the ULN has internal clamping diodes.
Right, I forgot this point. ULN2803 COM should be allowed to swing to double power supply, e.g. by adding a 12V zener diode between +12V and COM.

But an unipolar motor will still work at lower speed. Particularly the voltage measurements reported in the post can't be explained by clamping diode effects. It sounds like a much more trivial problem.

In any case, the main question is about bipolar stepper drive. Whatever's the problem with your unipolar motor, the bipolar motor doesn't work with ULN2803.
 
Hi,



Unipolar stepper motors cause a problem, if the ULN has internal clamping diodes.
Because of the bifilar winding configuration, you may expect twice the supply voltage at the "non activated" wire.

Disconnecting the ULN's COM from supply voltage may help.
If you still want an overvoltage protection, then connect a zener with at least twice the supply voltage at COM (and GND).

Klaus

I did what you said ..but still not working....just tell me how to find right winding sequence of bipolar stepper motor....cause my code is working on simulation!! but not on hardware,,,,Thanks!!
 

Right, I forgot this point. ULN2803 COM should be allowed to swing to double power supply, e.g. by adding a 12V zener diode between +12V and COM.

But an unipolar motor will still work at lower speed. Particularly the voltage measurements reported in the post can't be explained by clamping diode effects. It sounds like a much more trivial problem.

In any case, the main question is about bipolar stepper drive. Whatever's the problem with your unipolar motor, the bipolar motor doesn't work with ULN2803.

Hi,



Unipolar stepper motors cause a problem, if the ULN has internal clamping diodes.
Because of the bifilar winding configuration, you may expect twice the supply voltage at the "non activated" wire.

Disconnecting the ULN's COM from supply voltage may help.
If you still want an overvoltage protection, then connect a zener with at least twice the supply voltage at COM (and GND).

Klaus

Is it good way to use L293D for bipolar stepper motor?? Will it work??
 

L293 will work. But it's old bipolar technology with large saturation voltage and respective high power dissipation. A recent MOSFET bridge driver would be preferred.
 

Hi,

You have checked the coil pairs with an ohmeter? - I'm sure you have. Is the problem figuring out the frustrating sequence to get it to turn as wanted? - Maybe one of these links might help, and you can figure it out from deduction or an example:

3. Basic Stepping Motor Control Circuits

code, circuits, & construction: Stepper Motors

Wiring Connections

microcontrollers/breadboards: Driving a Bipolar Stepper Motor

If all else fails, and it isn't wiring type of error, doesn't hurt to try a few different patterns for driving the coils, these links have a variety, most are the same if I remember well:

http://en.wikibooks.org/wiki/Practical_Electronics/Stepper_Motors H-bridge and driver wiring

**broken link removed** "" ""

same sequence as above

http://vshamu.wordpress.com/tag/l293d/ seems in depth and has another step sequence

http://www.8051projects.net/wiki/Stepper_Motor_Tutorial different step sequence to above two.
 
Hi,

You have checked the coil pairs with an ohmeter? - I'm sure you have. Is the problem figuring out the frustrating sequence to get it to turn as wanted? - Maybe one of these links might help, and you can figure it out from deduction or an example:

3. Basic Stepping Motor Control Circuits

code, circuits, & construction: Stepper Motors

Wiring Connections

microcontrollers/breadboards: Driving a Bipolar Stepper Motor

If all else fails, and it isn't wiring type of error, doesn't hurt to try a few different patterns for driving the coils, these links have a variety, most are the same if I remember well:

L293 will work. But it's old bipolar technology with large saturation voltage and respective high power dissipation. A recent MOSFET bridge driver would be preferred.

Thanks to All for helping me!!!

I tried bipolar motor using L293D and works!!!!
Thanks again!!!1:lol::lol::grin::grin::grin::smile::smile::smile:
 

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