Shop OBEX P1 Docs P2 Docs Learn Events
Problem: low I/O voltage — Parallax Forums

Problem: low I/O voltage

spccowboy08spccowboy08 Posts: 2
edited 2007-02-01 18:57 in BASIC Stamp
I am having trouble with the voltage output on my BS2. When a pin is set to high, the output voltage is only ~2V. The 9v battery powering the stamp is well charged and the Vdd output is still 5V. Any ideas what could cause this?

Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2007-01-30 18:54
    What load are you trying to drive with that pin?

    If that load wants too much current, this can happen.
  • Mike GreenMike Green Posts: 23,101
    edited 2007-01-30 18:57
    The Stamp I/O pins can only supply about 20ma of current. If you have too low a resistance load on an I/O pin, the high voltage will "sag". You should not see this kind of low "high" voltage normally. If you need to drive a higher current load, you will need a transistor buffer. Look at the "What's a Microcontroller?" tutorial that you can download via Parallax's website and the Stamps in Education page for information on how to do this.
  • spccowboy08spccowboy08 Posts: 2
    edited 2007-01-30 20:24
    Increasing the load resistance upped the output. Thanks.
  • metron9metron9 Posts: 1,100
    edited 2007-02-01 18:57
    Measure the voltage across the load resistor, use ohms law to calculate the current draw.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Think Inside the box first and if that doesn't work..
    Re-arrange what's inside the box then...
    Think outside the BOX!
Sign In or Register to comment.