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(Unwanted) Blinking Outputs — Parallax Forums

(Unwanted) Blinking Outputs

Mag748Mag748 Posts: 269
edited 2004-09-01 02:31 in BASIC Stamp
While creating a circuit with LEDs, I noticed that when applying power the LEDs would start to blink rapidly. At first I thought it was the BASIC Stamp overloading or something because I have the LEDs connected directly from Vdd to Vss w/ out a 470 Ohm resister like all the manuals say you should. But then I Made a circuit without the stamp at all and the blinking still happened. Does anyone know why this is? I would assume its not a good sign.

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Comments

  • Buck RogersBuck Rogers Posts: 2,187
    edited 2004-08-31 04:40
    Hello from Buck Rogers
    Actually, yes. Your P/S--Power Supply, could be at fault. One of your capacitors could be going. What kind of supply is it?idea.gif



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    Buck Rogers

    www.gregg.levine.name
  • Mag748Mag748 Posts: 269
    edited 2004-08-31 05:36
    the PS like the Wall pack? its a parallax 9V pack. If thats what you mean.
    The caps your talking about, like the ones built into the BOE rev C that Im using?

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  • Buck RogersBuck Rogers Posts: 2,187
    edited 2004-08-31 06:05
    Hello from Buck Rogers
    Yes exactly. I've seen caps get punctured from too much voltage past their ratings. These are polarized electrolytics that I am writing about here. They typically contain a specific dielectric or insulating compound, to create that compound, a voltage is applied a certain way. And your power supply is a wall wart that the company provided, so that's not a problem. Not yet.

    Also I have seen my BS1 stamp cause the blinking to happen when first started up, it was executing the last written program, which happened to be one of that sort.

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    Buck Rogers

    www.gregg.levine.name
  • Mag748Mag748 Posts: 269
    edited 2004-08-31 06:15
    well the caps certainly arent 'punctured' and the program is just "OUTS = %1111111111111111" so that isnt causing them to blink either. I still am not sure what the problem is.

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  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2004-08-31 06:31
    HUH???

    from your first E-mail on this topic....
    Mag748 said...
    ...because I have the LEDs connected directly from Vdd to Vss w/ out a 470 Ohm resister like all the manuals say you should


    ... w/ out a 470 Ohm? I think that you SHOULD have a 470 Ohm on each LED otherwise the LEDs might draw enough power to drop the voltage
    enough that the STAMP will go into reset mode.

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    Beau Schwabe - Mask Designer III

    National Semiconductor Corporation
    (Communication Interface Division)
    500 Pinnacle Court, Suite 525
    Mail Stop GA1
    Norcross,GA 30071
  • bobhillierbobhillier Posts: 27
    edited 2004-08-31 13:36
    Hello Mag748

    You said you connected the LEDs from Vdd to Vss without an inline resistor. That results in a virtual short for the LED and will burn out a regular LED. Note: resistors are used to restrict the amount of current flow through a device.

    But your LEDs are not burned out. That means there is some form of inline resistor or current limiter.

    Where did you get these LEDs? I know they make blinking LEDs. I've never played with them. Maybe they do not require inline resistors because the resistor and blink circuit is built into them.

    Note for the future. If you do not use a resistor in-line with a regular LED you will burn out the LED. If it's connected to a Stamp there is a good possibility you'll burn out the Stamp pin.

    Get some resistors.

    ·

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    ······ Bob, Ottawa
    W75 54 17·· N45 18 30
    ·········· G16 #27
  • AlWilliamsAWCAlWilliamsAWC Posts: 135
    edited 2004-08-31 13:42
    Keep in mind that they do make 5V LEDs with the·resistors built it. We provide these with most of our Stamp-related kits and separately. I've also seen them at Radio Shack. When you are breadboarding they make a neater job since they don't require resistors. That being said, unless you are using these special (and relatively unusual) LEDs, you do need a dropping resistor!

    If you want to learn more about this sort of thing, drop by http://www.al-williams.com/classroom/course/view.php?id=4.

    Regards,

    Al Williams
    AWC
    Kits!
    http://www.awce.com/kits.htm

    P.S. Whoops. Too early. Said 5V resistors instead of 5V LEDs :-) Good thing for editing!

    Post Edited (Al Williams/AWC) : 8/31/2004 1:44:58 PM GMT
  • Harry StonerHarry Stoner Posts: 54
    edited 2004-08-31 18:40
    I recently bought some LEDs that had both an integrated resistor AND flashed - perhaps that is what he has? If the current was measured perhaps that would provide a clue.

    Harry
  • Buck RogersBuck Rogers Posts: 2,187
    edited 2004-08-31 18:55
    Hello from Buck Rogers
    I have a few here, as well. They've got the blinking device stuck off center to the regular LED chip.

    Also Agilent makes LEDs with the resistors installed already,

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    Buck Rogers

    www.gregg.levine.name
  • Mag748Mag748 Posts: 269
    edited 2004-09-01 01:59
    well, im gonna be honest now. The reason I was not using resistors was because the leds were a 10-segment LED Bar graph (purchased from radio shack) and I was too lazy to use 10 resistors, so I just stuck one side of the bar directly into the I/O pin header and the other end just chained to the Vss. So, I am prety sure now that the blinking was caused by the Stamp reseting itself over and over (Yes, I realize this is a very bad thing). So, I learned the hard way, ALWAYS use resistors.

    Hmm, Ill try looking for those 5V LEDs. They must have been made for the lazy folks, lol.

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  • Jon WilliamsJon Williams Posts: 6,491
    edited 2004-09-01 02:31
    Lazy kills....

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    Jon Williams
    Applications Engineer, Parallax
    Dallas Office
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