ULN2003

Discussion in 'General Electronics Chat' started by buddyengineers, Jun 11, 2005.

  1. buddyengineers

    buddyengineers Thread Starter Member

    Joined:
    Mar 19, 2005
    Messages:
    26
    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
  2. hgmjr

    hgmjr Moderator Staff Member

    Joined:
    Jan 28, 2005
    Messages:
    9,030
    Location:
    Tennessee, USA (GMT-6)
    Can you possibly post the schematic of your ULN2003 for everyone to see how you have connected up the device?

    Hgmjr
  3. thingmaker3

    thingmaker3 Retired Moderator

    Joined:
    May 16, 2005
    Messages:
    5,072
    Location:
    Rural, Oregon GMT -8
    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.
  4. pinball8

    pinball8 Member

    Joined:
    Jun 12, 2005
    Messages:
    16
    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.
  5. pinball8

    pinball8 Member

    Joined:
    Jun 12, 2005
    Messages:
    16
    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?
  6. thingmaker3

    thingmaker3 Retired Moderator

    Joined:
    May 16, 2005
    Messages:
    5,072
    Location:
    Rural, Oregon GMT -8
    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.
  7. buddyengineers

    buddyengineers Thread Starter Member

    Joined:
    Mar 19, 2005
    Messages:
    26
    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
  8. pinball8

    pinball8 Member

    Joined:
    Jun 12, 2005
    Messages:
    16
    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.
  9. mozikluv

    mozikluv AAC Fanatic!

    Joined:
    Jan 22, 2004
    Messages:
    1,437
    Location:
    Philippines

    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 :D :p :lol: :D

    moz
  10. kensplace

    kensplace New Member

    Joined:
    Jun 25, 2005
    Messages:
    7
    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.
  11. pinball8

    pinball8 Member

    Joined:
    Jun 12, 2005
    Messages:
    16
    Thanks. I started learning electronics in 1952, had my amateur radio license in 1956, radiotelephone in 1958, Navy electronics 61-63, college degree in 1967, silicon valley engineer 67-80, sound engineer for many major entertainment groups through 1990. I currently own 400 pieces of equipment spread over 200 miles. These include arcade games, pool tables, vending machines and jukeboxes. It is nice to be able to help someone else solve their problems. Anything I know is always free.
  12. surajmdth

    surajmdth New Member

    Joined:
    Jun 29, 2005
    Messages:
    1
    Were u trying to source current to your motor from the ULN2003?
    If yes...you are doing it wrong....you have to sink current from your motor.
    If no...we need to see your schematic...:)

    I have worked with ULN 2003 on hundreds of projects and they are fine chips....really rugged and do not burn often..they are stable..:)


    Suraj
  13. buddyengineers

    buddyengineers Thread Starter Member

    Joined:
    Mar 19, 2005
    Messages:
    26
    Thanks for the help again.., but my query is still not solved.

    We all had a lot of dicussions on why the motor is not working, but lets first solve the problem as to why the ULN is not providing the logical voltage, it should, at the output.

    Firstly..., I never tested the ULN connected to the motor. I first checked the output voltage of the ULN with the inputs from the Parallel Port, and was surprised to see the output as mentioned before.., thats why i said, no problem of Motor Back EMF affecting the operation of the ULN. The outputs mentioned above were from a general test done on the ULN before using it with the motors. Using the motors and all were just a part of my project which i was trying to implement using the ULN.

    Also i am posting the schematic.., no great work it is.., a very simple circuit, (thats exactly why i am still trying to find the solution to this.., bcoz am not able to work out the problem with this simple circuitry).


    As for Suraj.., u popped up a real nice thing abt sinking or sourcing current thru the ULN. Cant u source current to the motor through the ULN?.Do let me know about it. Also frankly speaking even i have worked with ULN's before, but this strange output confused me.., and i seriously tried out more than 6 IC's before finally giving up.

    [attachmentid=758]

    Thanks once again and i hope this information is sufficient to continue the discussion.
    Do let me know if u need any more information abt anything else.
    Also please do let me know if i have done any mistake in the circuit diagram.

    Cya
    Dilu
  14. thingmaker3

    thingmaker3 Retired Moderator

    Joined:
    May 16, 2005
    Messages:
    5,072
    Location:
    Rural, Oregon GMT -8
    I'm hoping that "DC Motor 1" and "DC Motor 2" are actually winding one and winding two of the same motor. Other than that...

    Did you have any load at all when measuring outputs?

    And now for some grasping at straws: Have you had any other problems using the same breadboard?
  15. Garry

    Garry Member

    Joined:
    Jul 1, 2005
    Messages:
    12
    Hm ... I may be totally off, but shouldn't the circuit look something like this:


    Code:
          ------+
            16|-----Motor-----VDD
            15|
            14|-----Motor-----VDD
            13|
             |
    
    Or are you trying to implement reversing the direction by either activating one line or the other and using the ULN as a source? Sounds wrong to me ... !?
  16. buddyengineers

    buddyengineers Thread Starter Member

    Joined:
    Mar 19, 2005
    Messages:
    26
    Hey Thingmaker..., they are two diff motors at all..., and not two different windings. No there was no load when i was trying to measure the output voltage across the ULN. And u must laugh now at me..., but i even tried by changing the BreadBoards. I have tried every possible error that can occur, but no help it has been. Thanks anyways for asking.
    yes the boards i have used have been used before for lot many testing works, and am assured they are perfect.

    And for Garry..., frnd ur right i am trying to implement the reversing action of the motors using the ULN, the current requirement of the motor is barely 1/2 Amp at max load, or even less than that, does it sound wrong.., so if thts the case it must mean tht i cant source current to the motor via the ULN. So then now the question arises for me tht the supply connected to the pin 9 is for wat purpose?
    1. Just to decide the voltage cut-off level (max) of the IC or
    2. To provide the load current also.

    Please let me know abt it frnd.
    Thanks anyways for helping
    Cya
    Dilu
  17. Garry

    Garry Member

    Joined:
    Jul 1, 2005
    Messages:
    12
    That's the free wheeling diode, needed e.g. for coils ...
  18. buddyengineers

    buddyengineers Thread Starter Member

    Joined:
    Mar 19, 2005
    Messages:
    26
    hey garry wat free wheeling diode are u talking abt.., i didnt get it
    cya
    Dilu
  19. Garry

    Garry Member

    Joined:
    Jul 1, 2005
    Messages:
    12
    Check the circuit diagram e.g. here for example ...
  20. kensplace

    kensplace New Member

    Joined:
    Jun 25, 2005
    Messages:
    7
    These chips sink current....
    You need 12v supply into the motor, then back out from the motors other wire to the output of the darlington, which will sink it to gnd (the other supply pin is connected to internal diodes for limited back emf protection)
Similar Threads
Forum Title Date
General Electronics Chat Problem with ULN2003A Feb 10, 2013
General Electronics Chat ULN2003 very confusing problem Jul 26, 2012
General Electronics Chat ULN2003 operation principle question Jul 20, 2012
General Electronics Chat difference between ULN2003 ULN2803 Jun 14, 2012
General Electronics Chat ULN2003 or single transistors May 27, 2012

Share This Page