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Professional Development Board's Pulse Generator Hot to touch — Parallax Forums

Professional Development Board's Pulse Generator Hot to touch

knightofoldcodeknightofoldcode Posts: 233
edited 2009-04-14 03:20 in BASIC Stamp
Board,

I purchased my PDB a few years ago, and it's mostly been in storage (haven't had time to do what I've wanted to, projects got on hold.) Now that I have a little bit of time, I've started playing around again. During storage, I couldn't find my wal wart that came with the board, so I used a universal from Radio Shack (universal voltage, I put it at 12V) only problem is that the amperage is too low, (300MA according to the wall wart) so the power LED came on for a second, then turned off, and continued to cycle for a second between each on/off. So I turned the wall wart down to a lower voltage, 9V, it now functioned correctly, and I started to play... programmed a BS2... Played a little with the LCD. After a few minutes I noticed that the Pulse Generator was getting hot....very hot. I immediately turned off the power supply, and have yet to figure out why it's gettign so hot. I have removed all socketed IC's, all jumpers, all wires, BS2, etc. No change. When powered from barrel jack the Pulse Generator gets hot (too hot to touch) within 1-2 seconds. I tried powering it with a 5V on VSS and VDD, same results. But again, everything else works perfectly!

I read previous posts about incorrect polarity... I have not done that. Nor have I ever hooked up a servo to this board. I don't think I've ever used the VIN either.

Also the 1K LED is illuminated permanently, when I press the button it dims until the button is released, but it never changes frequency. I seem to recall it defaults to 1 Hz frequency normally.

When running via VSS/VDD 5V (well regulated), it is right at .50 amps current being drawn/consumed without the BS2, but all other IC's present. 2.5 watts seems a little excessive?

No other IC appears to get hot. I connected power, waited until the Pulse Generator was hot, then I felt all other IC's and nothing else appears to get hot. I havn't tried letting it have power for more then about 15 seconds, so it may get hot after a while, but I would assume if they were having problems also, that they would get hot just as fast as the pulse generator.

My board is a PDB Revision B 2005, with USB built on board.

I am stumped. I can't figure it out. Any ideas? Or anything I should try/test/check?

Much thanks,
Knightofoldcode.

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Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2009-04-12 13:53
    Sounds like the pulse generator microprocessor is busted. Call Parallax Tech Support in the morning to see about getting the PDB repaired.

    There's not much to the pulse generator, just a PIC microprocessor, some LEDs, and a pushbutton. You might check for short circuits in the
    area of the pulse generator, but most likely the PIC is somehow damaged.

    Post Edited (Mike Green) : 4/12/2009 1:59:37 PM GMT
  • knightofoldcodeknightofoldcode Posts: 233
    edited 2009-04-12 21:31
    Mike Green,

    Thank you for your reply. I agree that it's most likely a damaged pulse generator. But 1) How?.... I don't think I've done anything that could destroy it. 2) I don't care much about it.... so is there any harm in not getting it repaired? IE, I just de-solder the chip myself, and leave it at that.... if I do that, what can I check to make sure nothing else is going to get damaged further down the road......

    I'm still of course interested in anyone else's opinions.

    Knight.

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    Light the man on fire, and he will be warm for the rest of his life.
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  • Mike GreenMike Green Posts: 23,101
    edited 2009-04-12 21:46
    1) Who knows? It may be a short somewhere on the PCB. It may be a bad PIC. The pulse output is protected with a 220 Ohm resistor. The LEDs and the pushbutton all have appropriate resistors.

    2) The problem in just removing the chip is that you still wouldn't know what happened. I'd still talk to Parallax Tech Support.
  • knightofoldcodeknightofoldcode Posts: 233
    edited 2009-04-13 00:48
    I don't know how much value this is, but I looked up the data sheet on the pulse generator (PIC12F629) and verified that pin 1 has +5VDC going to it, and pin 8 is ground. Voltage is right at 5VDC.


    Knight.

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    Light the man on fire, and he will be warm for the rest of his life.
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  • RDL2004RDL2004 Posts: 2,554
    edited 2009-04-13 16:14
    Just for the record, I measured the current used by my PDB once and it was only around 100 mA or so. So it seems you definitely have a problem.

    I only had a BS2 and and SX installed (I think, I may have had the logic analyzer module installed also). The SX wasn't running and the BS2 was running a very simple program and not supplying power to anything with it's pins.

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    - Rick
  • knightofoldcodeknightofoldcode Posts: 233
    edited 2009-04-13 19:54
    RDL2004 said...
    Just for the record, I measured the current used by my PDB once and it was only around 100 mA or so. So it seems you definitely have a problem.

    I only had a BS2 and and SX installed (I think, I may have had the logic analyzer module installed also). The SX wasn't running and the BS2 was running a very simple program and not supplying power to anything with it's pins.


    Much thanks for that information. The .5amps @ 5VDC that I measured was with NO basic stamp, all IC's removed (Audio Amplifier, 4CH Driver, Basic Stamp, SX28, etc). So as you say, it's certainly excessive. Thank you.


    Knight.

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    Light the man on fire, and he will be warm for the rest of his life.
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  • $WMc%$WMc% Posts: 1,884
    edited 2009-04-14 02:28
    Knight

    I have had some problems with the PULSE GENERATOR on My Pro.Dev.Boards.(All self inflicted) I zapped the first one(pulse gen.),I sent it to Parallax and they fixed it/replaced it in a super fast (NASCAR style pit stop) turn around. I zapped the next one about 8 months later. While the bad "ZAPPED" PULSE GENERATOR had no affect on the $BS2 series of stamps, it did effect the SX28. It killed its performance. I have to use the SX28 on a generic bread board.

    Maybe this will lead to a harder to blow fix for the PULSE GEN. circuit !


    ___________________$WMc%________

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  • knightofoldcodeknightofoldcode Posts: 233
    edited 2009-04-14 03:20
    $WMc% said...
    Knight

    I have had some problems with the PULSE GENERATOR on My Pro.Dev.Boards.(All self inflicted) I zapped the first one(pulse gen.),I sent it to Parallax and they fixed it/replaced it in a super fast (NASCAR style pit stop) turn around. I zapped the next one about 8 months later. While the bad "ZAPPED" PULSE GENERATOR had no affect on the $BS2 series of stamps, it did effect the SX28. It killed its performance. I have to use the SX28 on a generic bread board.

    Maybe this will lead to a harder to blow fix for the PULSE GEN. circuit !


    ___________________$WMc%________


    I sent it to Parallax...we'll see. As far as I am concerned, if they want to remove the IC all together, I think that would be fine with me.... just don't bother with a pulse generator. Maybe put it on a daughter board. What I would like to see is the IC be socketed!.... That way it's removed 90% of the time, except when I am using it... Or, put in a power switch to it....remove all 5V to it, unless you are using it.


    Knight.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-=-=-=-=-=-=-=-=-=-=-=-
    This message transmitted with 100% recycled electrons.
    -=-=-=-=-=-
    Gravity doesn't exist. The Earth sucks.
    -=-=-=-=-=-
    Make a man a fire, and he will be warm for the night.
    Light the man on fire, and he will be warm for the rest of his life.
    -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-=-=-=-=-=-=-=-=-=-=-=-
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