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Running the Prop Protoboard from a different 5v and 3.3v source? — Parallax Forums

Running the Prop Protoboard from a different 5v and 3.3v source?

eagletalontimeagletalontim Posts: 1,399
edited 2013-06-24 09:12 in Propeller 1
I have designed a power supply circuit to use for a prop project and need to test it in my vehicle. I am currently using an LM317 to adjust to voltage going into the prop protoboard down to 9V to prevent the board from getting too hot and popping any components. Is there a way to bypass the onboard power circuit without having to remove the regulators? I would like to power the protoboard solely from my circuit which outputs 5V and 3.3V.

Comments

  • eagletalontimeagletalontim Posts: 1,399
    edited 2013-06-23 20:39
    I take it this is not something anyone has done. I cannot use the existing circuit as the existing circuit is not in the final design.
  • cavelambcavelamb Posts: 720
    edited 2013-06-23 21:07
    http://cds.linear.com/docs/en/datasheet/lt0117.pdf

    Applications Section - page 7
  • eagletalontimeagletalontim Posts: 1,399
    edited 2013-06-23 21:22
    Not sure what that is for... The only reason the Prop board is installed in my car right now is because I was able to build a simple ADC circuit on it without losing much resolution. The final design will be on a custom circuit board that will have the power supply circuit board that I have already made and soldered up. This new power supply needs to be tested in the automotive environment under load of my current circuit. Since the Prop protoboard has it's own power regulating circuit, I must bypass this to only use the power that my power supply outputs. I do not want to use the protoboards existing regulators.
  • rjo__rjo__ Posts: 2,114
    edited 2013-06-23 21:34
    Hi Tim,

    I'm pretty sure you can just hook-up 3.3V to Vdd and ground to ground and you are good to go. I say pretty sure because I've never done it and haven't really looked at the regulators for a while. I think the point of cavelamb's post was so that you could resolve the issue of reverse current through the 3.3V regulator. I do know for sure that you can just cut out the Prop chip and surrounding assigned (dual pin) arrangements and then feed 3.3V to the gutted ProtoBoard. This is fun... there are some threads about it... don't know where, but someone will chime in if you are interested. The end result is a credit card size Prop board, which you can power with 3.3V to Vdd.

    IMHO, you need to order lots of 5 Protoboards... that way you can just do it!!!! And if it doesn't work, what the heck?

    Rich
  • kwinnkwinn Posts: 8,697
    edited 2013-06-24 09:12
    The 5V is simple. Short the 5V LM1086 input pin to the output and you can put 5V on the barrel connector. The 3.3V is a bit trickier. First you have to cut the connection between the 3.3V LM1086 input pin and the +5V (between C2 and C9), short the 3.3V LM1086 input and output pins, and connect your +3.3V supply to the C9 positive pin, and negative to C9's negative pin if required.

    Careful though. putting anything much higher that +5V in to the barrel connector could be bad.
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