How to use the UDN 2981?

Discussion in 'Analog & Mixed-Signal Design' started by jkcobain, Oct 14, 2016.

  1. jkcobain

    Thread Starter Member

    Jun 8, 2014
    Hello, everyone.

    I started a project where I use a UDN2981 in order to activate some 24v valves. When I put the input in high, I get the 24v at the output; the problem is that when the input is low, I get around 8v at the output. I tried with a pull down resistor at the input, but it doesn't change anything. So, how can I fix that problem? Any suggestions?

    Hope you can help.

    Thank you a lot in advance!
  2. hp1729

    Well-Known Member

    Nov 23, 2015
    How are you measuring the low output? With the load, or no load?
    GopherT and jkcobain like this.
  3. jkcobain

    Thread Starter Member

    Jun 8, 2014
    No load. I'm currently just testing in order to install it when I'm sure it's working. Could that be the cause for the voltage at the output?
  4. MaxHeadRoom


    Jul 18, 2013
    You have to measure it with a load, with a high impedance meter you are going to measure an unreliable reading through the IC.
    Use a a resistor in place of the valve if you want to test it.
    GopherT, atferrari and jkcobain like this.
  5. jkcobain

    Thread Starter Member

    Jun 8, 2014
    I did a quick test with a load, and it's 0v now. Never thought my problem was so silly haha! Thank you very much!!!
    GopherT likes this.