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How long can the Propeller stand 5v? — Parallax Forums

How long can the Propeller stand 5v?

william chanwilliam chan Posts: 1,326
edited 2008-08-18 13:46 in Propeller 1
My 3.3v regulator (LP2950-3.3) seems to be supplying 5.3v to the Vdd pins of the Propeller DIP chip.
I still don't know why.
When the Propeller chip is not connected, the Vdd pins measure 3.3v.
I removed the power about 20 seconds later when I realized this.

Do you think the Propeller is dead?

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Comments

  • AleAle Posts: 2,363
    edited 2008-08-18 06:45
    Well... it may be or not. Most probably you got 5 V or so at VCC through the clamp diodes, so one or more pins got 5V noting that the regulator gives 3.3V without load. Verify all pins to see which one is the one getting a bit too much voltage.
  • PraxisPraxis Posts: 333
    edited 2008-08-18 09:17
    Hi William,

    Do you have a bypass capacitor near the output of the regulator?

    If not the regulator may oscillate under load and that is the voltage you are seeing.

    Cheers Azlan.
  • william chanwilliam chan Posts: 1,326
    edited 2008-08-18 09:45
    Ale's suggestion is right on.
    One of the IO pins is getting 6v through a 3.9k resistor. Thanks.
    I have now removed this resistor.
    I wonder if it has killed the Propeller chip......

    BTW,

    I found that when the Prop Plug is plugged in to my board, it forces the Propeller chip's Vdd to rise up to about 4v.
    The source of this high voltage seems to come from the TX and Res pins of the Prop Plug.
    Is this normal?

    I am still unable to program the Propeller chip, now I get the "No Propeller Chip found on any serial port" message,
    even though both Prop Plug LEDs now blink when I try to "Identify Hardware".

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    www.fd.com.my
    www.mercedes.com.my
  • AleAle Posts: 2,363
    edited 2008-08-18 10:09
    I do not think you can kill the propeller through a 3.9k resistor and 6V... Are you sure TX and RX are not reversed ? (Have you been able to program that same Propeller with that same prop plug before the modifications that giave rise to this problem ?)
  • william chanwilliam chan Posts: 1,326
    edited 2008-08-18 11:15
    Ale,

    How many volts you got being output from the Prop Plug Tx and Res pins while plugged into a board?
    I changed to a new propeller D40 chip, but still cannot program.

    I double checked the Tx and Rx pins are not reversed.

    This is the 1st time I use this board and this Prop plug.

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    www.fd.com.my
    www.mercedes.com.my
  • AleAle Posts: 2,363
    edited 2008-08-18 11:41
    RES 3.3V (It is an open collector output)
    TX (Pin 40) 3.37 V

    Do you get echo (in a terminal program) if you short TX and RX in the prop plug (unplugged from any board) ?

    Do the regulator work ? (After getting 5V in its output)
  • william chanwilliam chan Posts: 1,326
    edited 2008-08-18 12:01
    Ale,

    The regulator seems to be robust.

    I tried shorting Tx to Rx in the Prop plug as you suggested.

    Only the blue LED blinks when I type something on the keyboard, using Parallax Serial Terminal program.
    The Red Led does not blink. No echoing.

    Looks like the Problem is with the Prop Plug.

    Unfortunately I don't have a spare Prop Plug...... cry.gif

    Looks like have to abandon my 1st real Propeller board project until I can get another Prop Plug, or should I put the Prop plug into a reflow oven?

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    www.fd.com.my
    www.mercedes.com.my

    Post Edited (william chan) : 8/18/2008 12:07:47 PM GMT
  • AleAle Posts: 2,363
    edited 2008-08-18 13:46
    Well... if you have access to a traditional RS-232 port... there is a circuit in the manual with 3 transistors... that could help.
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