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Author Topic: ULN 2803-  (Read 4810 times)

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Offline parthikTopic starter

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ULN 2803-
« on: March 17, 2008, 08:36:20 AM »
I am driving a unipolar stepper motor with a ULN 2803 and a avr ATMEGa32

the problem is that i have to increase the current input to the stepper motor to 1.7A(each motor) to make it run .
But the rating of ULN is 500mA which made me burn many ULN's...

My friend runs steppermotor using 1A(for both motors).

also can u show me a ULN circuit diagram? cause I have got it from a book so not sure if it would work. ....
I am using a 9v stepper motor and .8A current but when i fit the wheels , the stepper doesnt move until i increase the current upto 1.7A.
PLz help
« Last Edit: March 17, 2008, 12:05:42 PM by parthik »

Offline Rebelgium

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Re: ULN 2803-
« Reply #1 on: March 17, 2008, 09:13:26 AM »
If the ULN can only let 500mA pass, another circuit won't increase that...
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Offline parthikTopic starter

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Re: ULN 2803-
« Reply #2 on: March 17, 2008, 11:28:10 AM »
but how cme my motor consumes so much current?...

its a minebea unipolar stepper motor .

Offline izua

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Re: ULN 2803-
« Reply #3 on: March 17, 2008, 03:22:40 PM »
make a power stage with 4 transistors, or if you wish to do bipolar stepping, with two h-bridges.
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Offline Rebelgium

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Re: ULN 2803-
« Reply #4 on: March 18, 2008, 04:15:04 AM »
but how cme my motor consumes so much current?...

its a minebea unipolar stepper motor .

-because that's just a characteristic of that type of motor.
-because the motor shaft is jammed and the motor stalls.
-because you connected the the motor wires wrong.

choose one  ;)
I suspect the last choice most.
« Last Edit: March 18, 2008, 01:38:51 PM by Rebelgium »
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Offline paulstreats

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Re: ULN 2803-
« Reply #5 on: March 18, 2008, 07:47:31 AM »
here is a circuit showing a uln2003 driving a motor, it connects the same as the uln2803.



Ignore everything in the diagram but the uln2003, and just connect your microcontroller outputs to the left side of it where the 4 wires are now.

The 500ma rated current for the darlington array is for a single darlington set(pin), so if you had a couple of darlingtons you can probably connect them in such a way as to share the load between more than 1 pin. Before you do this, definately make sure that your stepper is connected properly otherwise it will just increase current draw

Offline ed1380

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Re: ULN 2803-
« Reply #6 on: March 18, 2008, 07:57:31 AM »
check the datasheet to see if stacking is allowed.
you could put them on top of each other and double the ouput
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Offline karmax

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Re: ULN 2803-
« Reply #7 on: March 27, 2008, 02:09:37 PM »
pls use driver with 4 transistor or attach 4 ic in parllel

 


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