1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Uln2003

Discussion in 'Datasheets, Manuals or Parts' started by joshua17ss2, Jun 11, 2008.

  1. joshua17ss2

    joshua17ss2 New Member

    Joined:
    Mar 31, 2008
    Messages:
    116
    Likes:
    1
    hey
    im working on a project that will control 20 SSRs operating at 24 volts.
    the relay board has a single input for the 24volt relay control circuit, and only require a short between the ground and the control pin for the selected relay. 24 volts will flow thought this short. i want to allow a microcontroller to run these relays i originally planned to use simple switching transistors to control each of the lines, but i wanted to use an IC as it would provide and neater circuit and less components.

    Could i use the ULN2003 to contor the lines by just connecting the control pin for the the relay to the control pin on the uln chip.

    Any help or ideas would be appriciated, i attached a image detailing the way i think it would be wired..
    thanks
    josh
     

    Attached Files:

  2. k7elp60

    k7elp60 Active Member

    Joined:
    Oct 21, 2003
    Messages:
    1,148
    Likes:
    18
    Location:
    Utah
    It should work ok, If the relays don't have a transcient protection diode across the coils I would connect the common pin of the ULN2003 to +24 so the internal diodes are the protection diodes.
     
  3. Ubergeek63

    Ubergeek63 Well-Known Member

    Joined:
    Apr 16, 2008
    Messages:
    1,886
    Likes:
    37
    that is exactly what the uln2003 is for. just tie off the common pin to the 24V supply and you are off to the races.
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. joshua17ss2

    joshua17ss2 New Member

    Joined:
    Mar 31, 2008
    Messages:
    116
    Likes:
    1

    well the problem i saw was that the ssr board uses a common ground and has its own power hook up,
    so can the uln provide me with the short needed to trigger the solid state relays on this board

    thanks
    josh
     
  6. mneary

    mneary New Member

    Joined:
    Feb 27, 2007
    Messages:
    4,502
    Likes:
    67
    Location:
    California USA
    Since your relays are solid state (no inductor), then you don't need to connect the common pin to +24. Your design will work fine.
     
  7. gramo

    gramo New Member

    Joined:
    Oct 2, 2006
    Messages:
    1,221
    Likes:
    23
    Location:
    Newcastle, Australia
    Good to see the ULN2003 in another project :eek:

    Just like mneary said, no need to connect the Common when non-inductive loads are being driven

    [​IMG]

    BTW - why don't you use logic level SSR's?
     
  8. Ubergeek63

    Ubergeek63 Well-Known Member

    Joined:
    Apr 16, 2008
    Messages:
    1,886
    Likes:
    37
    What are you controlling with the relays?
     
  9. joshua17ss2

    joshua17ss2 New Member

    Joined:
    Mar 31, 2008
    Messages:
    116
    Likes:
    1
    I bought the board and relays on ebay, i was looking to get some logic level relays but there 5 to 10 dollars a piece, i only paid 10 dollars for 20 relays and the board, i figure the buffer i need to make is well worth the savings. :)
    I already have a pile of the uln chips i use them in alot of my projects they are a great little chip.
     
  10. joshua17ss2

    joshua17ss2 New Member

    Joined:
    Mar 31, 2008
    Messages:
    116
    Likes:
    1
    I will be using the relays to control a bunch of lights. i do small shows for christmas, halloween and any other time i find a theme.
    This way i can move all the lighting control to a pic all its own. and connect them to the computer or another pic thats running the air valves, motors and everything else in the show.
     
  11. joshua17ss2

    joshua17ss2 New Member

    Joined:
    Mar 31, 2008
    Messages:
    116
    Likes:
    1
    ww.webbspinner.com

    this is the board i was using to control just 8 channels of lights before, im hoping that the ssr board will be much neater, and more compact and faster :) along with tripeling my availible channels.
    i will post come pictures of the new board when it is finshed, (that will be in a few months as all my electronics are packed and waiting to be moved to orlando.)
     
    Last edited: Jun 12, 2008
  12. shokjok

    shokjok Member

    Joined:
    May 14, 2008
    Messages:
    452
    Likes:
    3
    Location:
    Alberta, Canada
    I made a Christmas light controller with a 555, 4017 and 4N25 optos in 1988. Only had to replace the interface board after a small fire in 1997. That project is boxed away after 3 years of no lights hung up. A schematic is available, and can be interfaced with ULN2003A for other applications.
     
  13. joshua17ss2

    joshua17ss2 New Member

    Joined:
    Mar 31, 2008
    Messages:
    116
    Likes:
    1
    im hoping my design will have significanly less parts, the controller, the buffers, and the relay board
    Small parts count, easy wiring. and im using at 18F4550 so if i need to i can control it from my computer, at the moment im happy just writing the code for the microcontroller.
    since i will have the extra ports im thinking of adding an lcd and RF remote to select different shows on the controller.
     
  14. uaefame

    uaefame New Member

    Joined:
    Feb 22, 2008
    Messages:
    271
    Likes:
    9
    Location:
    Dubai, UAE
    Hello gramo,

    What program you are using to draw electrical circuit it seems interesting
     
  15. asif418

    asif418 New Member

    Joined:
    Jan 12, 2009
    Messages:
    4
    Likes:
    0
    Hello there,

    Hope you will be doing fine.I am in need of some help regarding ULN2003 operation with MSC1200 Microcontroller. I am using ULN2003 to control Relay (PE014F05-PCB, SPCO, 5VDC). Could you please advise me about the ULN2003A input circuit, can i directly connect the MSC 1200 port pins to input pins of ULN2003A? Or I have to do some thing else to drive relay from MSC1200 using ULN2003. ULN2003 will be power by 5VD. please do help me out, i will be very thankful to you.

    Kind regards
    Asif
     
  16. gramo

    gramo New Member

    Joined:
    Oct 2, 2006
    Messages:
    1,221
    Likes:
    23
    Location:
    Newcastle, Australia
    Do you mean something like this?
    [​IMG]

    The ULN2003 can be driven by logic voltages to provide an earth to the target circuit when a logic High is present at the input.

    You must connect Pin 9 of the ULN2003 to the positive supply of the relay to shunt back emf
     
  17. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,444
    Likes:
    936
    Location:
    Canada, of course!
    Why don't you look at the datasheet for the ULN2003A?
    It tells you all about it.

    Of course it can be driven directly from an output of a micro-controller like a PIC.
    See if your micro-controller has an output current of at least 125uA.

    But a ULN2003 has a voltage loss of about 0.8V at the low current for a relay so the 5V relay might not work.
     
  18. asif418

    asif418 New Member

    Joined:
    Jan 12, 2009
    Messages:
    4
    Likes:
    0
    Hello There,

    Yes I have checked the data sheet, but i am not confident that if i connect the MSC1200 port pins directly to the ULN2003A base (input) pins then the MSC port pins will be able to drive the ULN2003A. I have attached part of circuit diagram with this reply, hope this will give you clear picture and you will be in better position to help me out. The only thing I am intrested to know is that is this circuit OK? and if i directly connect the MCU pins to ULN2003A pins will MCU pins be able to drive the ULN2003A? or i have to pull up the p0 and p1 in order to drive the ULN2003A.

    Many thanks in advance, looking forward to your suggestions and help.

    Best regards
    Asif
     

    Attached Files:

  19. asif418

    asif418 New Member

    Joined:
    Jan 12, 2009
    Messages:
    4
    Likes:
    0
    ULN2003 circuit

    Hello There,

    Yes I have checked the data sheet, but i am not confident that if i connect the MSC1200 port pins directly to the ULN2003A base (input) pins then the MSC port pins will be able to drive the ULN2003A. I have attached part of circuit diagram with this reply, hope this will give you clear picture and you will be in better position to help me out. The only thing I am intrested to know is that is this circuit OK? and if i directly connect the MCU pins to ULN2003A pins will MCU pins be able to drive the ULN2003A? or i have to pull up the p0 and p1 in order to drive the ULN2003A.

    Many thanks in advance, looking forward to your suggestions and help.

    Best regards
    Asif
     

    Attached Files:

  20. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

    Joined:
    Jan 4, 2007
    Messages:
    21,185
    Likes:
    644
    Location:
    Ex Yorks' Hants UK
    hi,
    look at these images.

    Why have you connected the ULN drivers in parallel.?

    What is the current or resistance of the relay coil.?
     

    Attached Files:

    Last edited: Jan 13, 2009
  21. asif418

    asif418 New Member

    Joined:
    Jan 12, 2009
    Messages:
    4
    Likes:
    0
    Hello,
    I am using TYCO ELECTRONICS PE014F05 5V SPCO PCB relay. http://www.electro-tech-online.com/custompdfs/2009/01/63899.pdf
    Coil resistance is 125 OHM (datasheet) and verified by multimeter. coil power is 200mW. why i connect ULN drivers in parallel is to increase the current to the coil. The relay is a Single Pole Change Over relay ie if coil power is removed it maintain its last state and in my circuit i just have to power the relay for 30ms to 40ms. But if you have any better idea plz do tell me. Other main factor i am afraid of is that if i directly connect MSC1200 port pins to ULN will that work or i have to pull up the MCU pins in order to make circuit working. Any suggestion/ideas/help??????

    Best regards

    Asif
     

Share This Page