Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Problem Using Bipolar Transistor as a Switch

  1. Dec 21, 2012 #1
    Im new here and Im currently working on a small IR encoder project. I have the encoder working great but now I need to use the 5vdc signal that comes from the encoder and make it 24vdc. I am currently trying to use a bipolar transistor but its not working. The basic diagram that Im going off of is attached along with the schematic of the optical encoder schematic. Am i way off track or am I missing something obvious.

    BTW im using 20k for R1 and 200K for R2 for the switch
     

    Attached Files:

  2. jcsd
  3. Dec 21, 2012 #2

    berkeman

    User Avatar

    Staff: Mentor

    Welcome to the PF.

    Can you run the first stage off of 24V? A 5V pullup stage will not shut off a 24V high-side switch stage...
     
  4. Dec 21, 2012 #3

    berkeman

    User Avatar

    Staff: Mentor

    If you can't run the first stage at 24V, use an open-collector stage to convert from 5V to 24V.
     
  5. Dec 21, 2012 #4
  6. Dec 21, 2012 #5

    berkeman

    User Avatar

    Staff: Mentor

    Your link is just a DC-DC converter to convert a 5V power supply to a 24V voltage source.

    What you want is a way to convert a 5V logic signal to a 24V logic signal, correct?

    The way to do that is with an open-collector BJT stage. Are you familiar with those yet?
     
  7. Dec 21, 2012 #6
    Ya thats correct. Im not familiar with those yet. Is that something that I could make or is that something that I should just buy?
     
  8. Dec 21, 2012 #7
    ok dumb question sorry I just looked it up and I think i can manage one of those. Thanks for the advice! Ill let you know how it goes!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Problem Using Bipolar Transistor as a Switch
Loading...