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Voltage fault on Demo board — Parallax Forums

Voltage fault on Demo board

PoeniePoenie Posts: 1
edited 2011-03-23 08:37 in Propeller 1
I got a propeller chip demo board. Currently doing an internship, so still learning. The problem is when I plug it in, do not get the correct voltage at the regulators. With a 9V input, I get 2.6V after the first VReg and 2.3V after the last. When I reduce the input to 4.5V I get 4.3V after the first and 2.8 after the second. Thus the output is inversely proportionate to the input. What can cause this?

Comments

  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2011-03-23 02:17
    Some regulators require a load before they give a valid output voltage, otherwise it could be that there is an overload somewhere. Heat should tell you the difference. With just a prop on idle there should be next to no warmth, but valid 5 Volts and 3.3 Volts.

    Is the power supply good and solid. If that was unstable then all sorts of lies could be told on your meter.


    Welcome to the Prop, people will turn cartwheels, here, to help.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-03-23 08:37
    What kind of power supply are you using? Some wall transformers are inadequately filtered, especially those sold as battery chargers. That may well be the case with your 9V unit. Either that, or whatever you were using was not able to supply enough current.

    The outputs with your 4.5V supply could be right, BTW. Every linear regulator has a "drop out" voltage. This is the voltage which must be added to the output voltage to yield the minimum input voltage. From your figures the 5V regulator appears to have a 0.2V dropout; the 3.3V regulator, 1.5V. So you need at least 5.2V on the input -- preferably at least 6V.

    -Phil
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