ULN2003

[buddyengineers]

Hello frnds..,
I am having some problem while working with ULN2003. The application desired was to run two 12v stepper motors and two 12v DC motors via the parallel port. Two different circuits were designed for the two diffrnt applications, as they were two diffrnt projects.

Pin 8 of ULN and parallel port ground were shorted with the ground of the power supply of 12v.
Pin 9 of ULN was connected to the 12v power supply.
The output from the parallel port was connected to the inputs from pin1 and so on.

All connections properly done, the ULN connected to the DC Motor circuit gave the following readings.
For logic 0 at the input: Output of ULN is 2.2v
For logic 1 at the input: Output of ULN is 0v

After 1 day:
For logic 0 at the input: Output of ULN is 0v
For logic 1 at the input: Output of ULN is 0v

I have not used ULN before but know that it works as a voltage buffer and current amplifier.

I mentioned about the stepper motors earlier, it was a circuit designed for my friends, and the stepper motor runs perfectly, sadly i didnt get to see their operation.

If anybody who has worked with ULN2003 can help me with this, it will be fondly appreciated. Though after 2 days i had to chuck the ULN's and go the conventional way of using BJT's and relays to drive the motors. But this ULN2003 has been a quest for me all the time. I dont why it gave me all the problem in the world., and my frnds not. I changed 6 ULN's before giving up.

Sorry for the long question, but was actually frustrated on not able to make such simple things work.

Dilu

[hgmjr]

Can you possibly post the schematic of your ULN2003 for everyone to see how you have connected up the device?

Hgmjr

[thingmaker3]

Your darlingtons are probably getting fried by back-EMF from the motor. Try adding a 12 or 15 volt zener diode between the 12V power supply and pin 9.

[pinball8]

Originally posted by thingmaker3@Jun 11 2005, 10:32 PM
Your darlingtons are probably getting fried by back-EMF from the motor. Try adding a 12 or 15 volt zener diode between the 12V power supply and pin 9.

Quoted post

Your part is a discontinued ECG 2013. It is only capabile of handling 1/2 amp of current overall. You need to use a power transistor to control the motors. The IC should only control the base of the power transistor.

[pinball8]

Originally posted by buddyengineers@Jun 11 2005, 01:12 PM
Hello frnds..,
I am having some problem while working with ULN2003. The application desired was to run two 12v stepper motors and two 12v DC motors via the parallel port. Two different circuits were designed for the two diffrnt applications, as they were two diffrnt projects.

Pin 8 of ULN and parallel port ground were shorted with the ground of the power supply of 12v.
Pin 9 of ULN was connected to the 12v power supply.
The output from the parallel port was connected to the inputs from pin1 and so on.

All connections properly done, the ULN connected to the DC Motor circuit gave the following readings.
For logic 0 at the input: Output of ULN is 2.2v
For logic 1 at the input: Output of ULN is 0v

After 1 day:
For logic 0 at the input: Output of ULN is 0v
For logic 1 at the input: Output of ULN is 0v

I have not used ULN before but know that it works as a voltage buffer and current amplifier.

I mentioned about the stepper motors earlier, it was a circuit designed for my friends, and the stepper motor runs perfectly, sadly i didnt get to see their operation.

If anybody who has worked with ULN2003 can help me with this, it will be fondly appreciated. Though after 2 days i had to chuck the ULN's and go the conventional way of using BJT's and relays to drive the motors. But this ULN2003 has been a quest for me all the time. I dont why it gave me all the problem in the world., and my frnds not. I changed 6 ULN's before giving up.

Sorry for the long question, but was actually frustrated on not able to make such simple things work.

Dilu

Quoted post

The ULN2002 crosses over to an ECG 2013. This is a display driver. It can only handle a few milliamps of current on each output. You must use a power transistor between the IC and the motor that can handle the current. What in the heck are you building?

[thingmaker3]

Originally posted by pinball8@Jun 12 2005, 02:29 AM
Your part is a discontinued ECG 2013. It is only capabile of handling 1/2 amp of current overall. You need to use a power transistor to control the motors.

Quoted post

The ULN2003 and it's NTE clone can both handle half an amp per channel. If the motors are small enough, then what Dilu is trying will indeed work. This is an old trick typically demonstrated with stepper motors from dead disk drives.

[buddyengineers]

Thanks frnds for all the replies..,
My quest still remains..,

Solving all the queries:
1. I will try and post the schematic of the design asap.

2. The ULN's were tested, and the outputs i mentioned were before connecting the motors to the IC output, so no concerns about Back EMF from the motor troubling the operation of the device.., but a real good suggestion that was.

3. Am using an SMPS(regulated power supply) so i didnt find the need to connect the Zener diode.., i think the zener is there to just regulate the power supply voltage at the zener level.

4. Someone mentioned here about ULN being used as a Display Driver.., but the datasheet that i referred clearly said it as Stepper Motor Driver, also i think the current needed for my motor is sufficiently provided by the IC.

5. And about wat i was trying to make with the ULN's..., I was controlling two 12v DC Motors over the internet using Java RMI. So the dedicated server for the application has my DC Motor driver circuit connected to the parallel port. I am using Native Methods in Java to send the signals to the parallel port. Now for driving the 12v DC Motors, i intended to use ULN 2003, but sadly it just didnt work somehow, so finally i used BJT's and Relays to drive the motors, and my project is working fantastic. I think this information should be sufficient to know about what my work was. If u need anything else, let me know.

Thanks once again for the replies.., but let me know., i have went wrong somewhere, i think i was doing some stupid mistake while testing the ULN's

Cya
Dilu

[pinball8]

Originally posted by thingmaker3@Jun 12 2005, 04:10 PM
The ULN2003 and it's NTE clone can both handle half an amp per channel. If the motors are small enough, then what Dilu is trying will indeed work. This is an old trick typically demonstrated with stepper motors from dead disk drives.

Quoted post

this is a fun place. i will never give any advice to anyone if i don't know the answer myself. i hope you people don't mind if i contribute.

[mozikluv]

Originally posted by pinball8@Jun 19 2005, 05:07 AM
this is a fun place. i will never give any advice to anyone if i don't know the answer myself. i hope you people don't mind if i contribute.

Quoted post

hi pinball8,

welcome aboard! yes we would mind if you won't contribute, we need people like you who has the time to help out :P :lol:

moz

[kensplace]

Did the motors run on the first day?

Not a electronics expert, but have used the uln2003 a few times, I normally get near supply voltage on a logic 0, and about 1 volt or so on a logic 1.

If after 1 day you are getting 0 volts on both, then it sounds to me like the previous suggestion of back emf is the cause, either that or your motors are taking more than 500ma out of the channel, burning the darlington out over time.

Just because the motors were not connected when you last took a reading does not mean anything, if the device has ALREADY been fried by over current or back emf then it is dead, and will give faulty readings whether something is connected or not.

Over stretching the device will often not kill it instantly it coud die after a day or so, stick diode in the circuit to protect against the back emf, also what is the motor coil resistance? You can work out the current used by the motor with ohms law, supply volts divided by coil resistance to get current used. If its more than half a amp, then thats your problem.

A schematic would be useful, even if you just say exactly what is connected to what pin, to make sure everything is ok circuit wise.