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Propeller Interface with 5v control signals — Parallax Forums

Propeller Interface with 5v control signals

tjbtjb Posts: 3
edited 2012-03-05 19:55 in Propeller 1
I have written some Basic Stamp apps and used interface boards such as motor controller, solid state relays, stepper motor control boards that need a 5v signal. The Propeller only has a 3v signal. How do I interface with the 5v peripherals? Thanks

Comments

  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2012-03-05 17:22
    Welcome to the forums!

    You'll find many posts on this subject - here is one to get you started...

    http://forums.parallax.com/showthread.php?127546-A-Cheap-easy-way-to-interface-Prop-with-5V-Peripherals
  • kwinnkwinn Posts: 8,697
    edited 2012-03-05 17:25
    For outputs from the prop going to inputs on the interface you can connect directly or use a 120 - 240 ohm resistor. Inputs from the interface to the prop need to a a minimum of a 3.3K series resistor to limit the input current on the prop pin.

    Most of the time a 3.3V signal is enough to drive 5V circuits, but if you have a lot of intermittent problems try using a level converter.
  • tjbtjb Posts: 3
    edited 2012-03-05 18:14
    Well thanks for the reply, I really do appreciate the suggestions. All I really want to do is program my propeller and interface to the stepper motor and servo control boards that use a 5v interface. I really don't want to get into an ee design cycle(I'm not an ee, I'm a programmer). I just want a simple solution for interfacing. The 3.3k solution for siganls to the Prop sounds easy enough. Going from the Prop to the control boards, I don't know. Thanks
  • CircuitsoftCircuitsoft Posts: 1,166
    edited 2012-03-05 18:17
    What servo control board are you using? It may have been done before.
  • tjbtjb Posts: 3
    edited 2012-03-05 19:44
    I purchased the stepper motors from Oriental directly along with the matching controller modules. I will take a look at the docmentation. Maybe I can adjust the upper voltage threshold down to 3.3v. Thanks for the interest and outreach.
  • Mike GreenMike Green Posts: 23,101
    edited 2012-03-05 19:55
    Most standard CMOS parts are designed these days to treat any input voltage above about 2.5V as a logic one and any input voltage below that as a logic zero, so a 3.3V output like the Propeller's will normally drive a 5V input just fine. Sometimes a controller will have some kind of funky input circuit that has different thresholds. There is a long "sticky" thread that addresses interfacing 3.3V and 5V devices in detail. Look here under "Technical Considerations". In your Oriental controller documentation, look for Vih (Voltage Input High) and Vil (Voltage Input Low) for specification of the minimum threshold for logic 1 and maximum threshold for logic 0. Probably you can connect your Propeller directly to the controller's input terminals, but the documentation has the final say.
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