Shop OBEX P1 Docs P2 Docs Learn Events
Don't do this, you'll feel stupid... — Parallax Forums

Don't do this, you'll feel stupid...

Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
edited 2007-08-27 13:26 in Propeller 1
There used to be a thread around here. (can't find it now) for confessions of stupid things you've
done with the Propeller. I can say I finally have had mine long enough to do something really dumb.
(I'm officially blaming lack of sleep, playing late night)

I was doing some re-work on one of my proto's when I got a glob of extra solder between some of my
pins. Not wanting to undo everything, I did what I've done in the past on some of my prefboard projects,
I grabbed my razor knife and pulled some neat slices across the PCB. Fixed the short, but cut
traces to TX/RX, P10, and P12.. A quick fix of the TX/RX and I rebooted to find the other two.

Boy do I feel stupid...

Joining the ranks.....

Oldbitcollector

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
The comments and code above are proof that a million monkeys with a million propeller chips *could* write Shakespeare!

Comments

  • RDL2004RDL2004 Posts: 2,554
    edited 2007-08-25 19:06
    I was going to change the green LED on my SX proto board to a different color. After I got the green one out I looked at the schematic to see what size current limiting resistor was used and discovered it was actually a resistor LED (resistor built in) and there was no way to use a normal LED in that spot. So I soldered in a blue LED with resistor in the proto-typing area - but it didn't work. I finally figured out that one of the holes for the original LED was used as a via and ALL the power to the proto area had to pass through there. I'm sure it was a plated through hole originally, but it wasn't after I was done with my surgery [noparse]:)[/noparse] I wasted at least an hour trying to figure out what was wrong.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Rick
  • deSilvadeSilva Posts: 2,967
    edited 2007-08-25 22:25
    Blue LEDs.... The SX board is most likely a 5V system.
    I'd like to prevent you from further disappointments: BLUE and WHITE LEDs have forward voltages between 3 and 3.5 V, so there is little chance to use them from the Prop without "drivers" connected to a higher voltage

    The shining HYDRA board has its blue LED near the power switch only smile.gif

    Post Edited (deSilva) : 8/25/2007 10:40:29 PM GMT
  • RDL2004RDL2004 Posts: 2,554
    edited 2007-08-26 00:48
    Sorry, I didn't mean to confuse you. I did say SX Proto board, not Propeller. I was only relating a similar mishap that happened to me recently. The board in question is well fixed and working fine, as is my Propeller proto-board with it's 3.3 and 5.0 volt power supplies. You do bring up an interesting question though, will a blue or white LED run off the 3.3 volt supply? What size current limit resistor is needed?

    The first picture shows where I patched in a wire to connect the top power trace to the bottom where the original LED was (I didn't bother to photograph the bottom), the second picture is just the blue LED happily making blue light.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Rick

    Post Edited (RDL2004) : 8/26/2007 1:03:28 AM GMT
    SX_0308.jpg
    480 x 319 - 127K
    SX_0304.jpg
    480 x 319 - 133K
  • deSilvadeSilva Posts: 2,967
    edited 2007-08-26 01:27
    RDL2004 said...
    You do bring up an interesting question though, will a blue or white LED run off the 3.3 volt supply?
    No, I am not bringing up an interesting question - I tell you, they will not!
    Well, most likely not smile.gif
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2007-08-26 02:03
    I'm positive I've run both white and blue off 3.3v.. Got an assortment a while back from Ebay..
    Will have to re-test...

    [noparse]:)[/noparse]

    Oldbitcollector

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    The comments and code above are proof that a million monkeys with a million propeller chips *could* write Shakespeare!
  • deSilvadeSilva Posts: 2,967
    edited 2007-08-26 02:24
    Well if you MUST shine blue LEDs and have some 5V somewhere, you can connect them as "collector load" and use the Prop Pin as sink (what you generally did in the old days, when pins couldn't drive at all from HIGH...)
    + 5 V --- resistor --- blue LED  --- Prop


    As they have a forward voltage of 3.3 V +/- 10% and LOW is around 0.3 V you have 1.4 V at the resistor
    If you want to SHINE them, use 100R (= 14 mA)
    But they also look good at economical 3 mA -> 470R
  • RDL2004RDL2004 Posts: 2,554
    edited 2007-08-26 04:11
    You know, the more I think about it the more I think that sending all the proto area power through that pin is a bit of a desigtn flaw. It works and I'm sure it falls within all tolerances, but I know I wouldn't do it that way.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Rick
  • SkogsgurraSkogsgurra Posts: 231
    edited 2007-08-26 09:28
    Why not? A via is a via.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
  • epmoyerepmoyer Posts: 314
    edited 2007-08-26 22:47
    Ok, speaking of stupid things....

    I was soldering a ground post onto my Hydra and I accidentally picked the wrong side of one of the bulk tantalums (+5V instead of GND). That would have been fine, and I would have figured it out soon enough, but I still had the Hydra connected to my Laptop over USB. The Hydra power was unplugged, but the board was getting 5V from the laptop, and soldering irons are electrically tied to ground, so....

    The laptop went down HARD. Just one big THUNK and all everything wend dark. I thought I had fried the whole thing. My heart was totally in my stomach.

    After unplugging everything I power cycled the laptop and everything came back up, but I'm much more careful about where I point that iron now [noparse];)[/noparse]
  • parts-man73parts-man73 Posts: 830
    edited 2007-08-27 13:26
    A couple years ago, my laptop battery was almost dead. I grabbed the power cord and tried to quickly plug it in. Blindly reaching around back I accidentally hit a USB port.....

    well, you remember that thread awhile ago about magic smoke??? I guess USB ports weren't built to sink 18 volts.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Brian

    uController.com - home of SpinStudio
Sign In or Register to comment.