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LED problem — Parallax Forums

LED problem

pwernerpwerner Posts: 5
edited 2006-11-07 17:39 in Learn with BlocklyProp
Apologies if this is something simple I'm overlooking, but I am working through the What's·a Microcontroller tutorial and I ran across a problem.· When building a LED circuit my LED isn't lighting up.· It did the very first time I tried it, then when I went to write a program that would make it blink once per second - nothing.· Now I can't even get the LED to light at all.· Ideas?

Comments

  • mage2mage2 Posts: 2
    edited 2006-11-06 16:39
    First make sure the LED works. Then check the connections.
    If you have a MultiMeter (everyone should), check and see if you are getting power during the pulse.
    Also what is the program you wrote?
  • pwernerpwerner Posts: 5
    edited 2006-11-07 15:05
    The program was the suggested program from the book:

    DO
  • pwernerpwerner Posts: 5
    edited 2006-11-07 15:06
    The program was the suggested program from the book:

    DO
    HIGH 14
    PAUSE 500
    LOW 14
    PAUSE 500
    LOOP
  • Beau SchwabeBeau Schwabe Posts: 6,566
    edited 2006-11-07 16:46
    pwerner,

    "It did the very first time I tried it, then when I went to write a program that would make it blink once per second - nothing."

    A couple of questions:

    Did you breakdown and rebuild your circuit from the first time?
    The LED does have a polarity, in the event of rebuilding your circuit, did the LED get reversed?
    Are you using a current limiting resistor in series with the LED? If not you could have burnt the LED out.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • pwernerpwerner Posts: 5
    edited 2006-11-07 16:49
    Yes, I did break down the circuit and rebuild it. I am using a 470 ohm resistor as instructed. I wondered if maybe I had burned the LED, but even when I attempted the circuit again with another LED I got the same results. Could the board be damaged?
  • Beau SchwabeBeau Schwabe Posts: 6,566
    edited 2006-11-07 17:20
    pwerner,

    If you were using the 470 Ohm resistor, it is highly unlikely that you burnt out the LED. I also noticed that your code uses pin 14.... The likely candidates would be that the
    LED is reversed, or you are not connected to p14 (This is the Physical pin 19 on the 24-pin DIP BS2 package)

    looking over the obvious... have you checked your battery?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • pwernerpwerner Posts: 5
    edited 2006-11-07 17:39
    I did think to look at the battery yes. It's new and fully charged. I'll check the LED again this evening. Thanks for the suggestions.
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