Low voltage control (ULN2003A )

Discussion in 'General Electronics Chat' started by Jack Xiu, Jan 18, 2018.

  1. Jack Xiu

    Thread Starter New Member

    Jan 18, 2018
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    I have a project. To get an output of +12V for High or 0V for Low, the maximum current is 25mA. As tm4C123 can output 5V or 3.3V and small current. I choose ULN2003. Could anyone have such experiences on the wiring please?
    upload_2018-1-18_7-21-33.png
     
  2. ericgibbs

    Moderator

    Jan 29, 2010
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    hi Jack,
    Welcome to AAC.

    The ULN2003 is an Inverter, so for +5V input you will see a close to 0V output, like wise a 0V will give a +12V output when using a 12V supply.
    E

    EDIT:
    You could consider a UDN2981
     
    Last edited: Jan 18, 2018
  3. Alec_t

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    Sep 17, 2013
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    Is the 25mA a sink current (output low) or a source current (output high) or both?
     
  4. ElectricSpidey

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    Dec 2, 2017
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    Yea, the ULN2003 can’t source current, only sink.

    AKA can't output +12 volts. (open collector NPN Darlington)

    If you choose the UDN2981, be sure to use a reputable source because they are obsolete, and there are counterfeits on the market.
     
  5. GopherT

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    Nov 23, 2012
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    If you are connecting to an INPUT logic of your DEVICE, you need to add a resistor from the UNL2003A to a 12V supply (1k to 10k is typical and depends on the speed, input capacitance and impendence of your DEVICE. Then, connect your DEVICE to the node between resistor and ULN2003A. As said above, the output will be inverted. If an inverted signal does not work for you, run it through an open block on the UNL2003A to invert it again (resistor to +12 on each is needed).

    If you are driving (powering) the DEVICE, then you can just connect the (-) of DEVICE to an output pin (collector) of the ULN2003A and the (+) of DEVICE to 12V.
     
  6. AnalogKid

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    What is "my device"? What is its power source? How much current will it draw at the input you show?

    Without more information, all responsess are guesses, not answers.

    ak
     
  7. ElectricSpidey

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    Dec 2, 2017
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    I would have to assume (bad idea?) his device is the tm4C123, and remember he is using right to left on his diagram.

    And I would imagine the area with the question mark could be replaced with simple logic inverters.

    But yup…all guesses.


    Well…looking at it again his diagram does not match the text.
     
    Last edited: Jan 18, 2018
  8. GopherT

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    The don't think so, see the "input" on far left (into ULN2003A)? It looks like everything is flowing left to right. He just doesn't show output or action of DEVICE.
     
  9. ElectricSpidey

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    Yea, but his text says something else.
    :confused:
     
  10. GopherT

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    That is not how I read it. Since the tm4C123 cannot (does not) need 12v, I assume the tm4C123 is to the LEFT of the ULN2003A and driving the input of ULN2003A. Therefore, circuit would be (is) drawn in standard left to right flow.
     
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  11. ElectricSpidey

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    Ok, I see what you are saying.
     
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  12. crutschow

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    Mar 14, 2008
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    You could also possibly use a 74LS07 Hex open-collector output buffer chip to do the conversion.
     
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