Warning! Blinking LEDs

Discussion in 'General Electronics Chat' started by hspalm, Nov 29, 2012.

  1. hspalm

    Thread Starter Active Member

    Feb 17, 2010
    201
    8
    I was breadboarding this http://www.goodluckbuy.com/rf-wireless-ask-super-regeneration-receiver-module-r02a-2pcs.html with a green LED on the VT (valid transmission) pin, and red LEDs on the four data pins. Each time I pressed a button on the remote, the VT pin would go steady high, and the corresponding data pin would blink. I have designed two circuits to make my data pins go steady high as the VT pin does, one which I failed to prototype and one using a small 8-pin microcontroller (that was my cheat). I also spent alot of time contacting the manufacturer of the chip "Silvan Chip" on skype and through their hotmail address, trying to find a chip version with non-blinking outputs. They had no idea what I was talking about.

    Anyways, I laid out the PCB design and sent off to manufacture (only 10, as a prototype). I then cleared the project from my desk and started a new one. Prototyped this project also on breadboard, using the same red LEDs as before. When this also had the same blinking effect when the LED was lit, I finally found out (after reprogramming my mcu for at least an hour) that I was using blinking LEDs, the kind that blinks by itself with a steady supply.

    This has cost me alot of time, especially waiting for replies from the manufacturer and postponing the PCB design. I am a novice, yes. Thank you for your time.
     
  2. DenzilPenberthy

    New Member

    May 28, 2012
    20
    7
    Things like that happen to everyone occasionally :) I spent three days once trying to debug some software which refused to work correctly. Eventually I realised I was editing a file called something-something but after every change I was running a file called something_something. No wonder my changes wouldn't fix the bug!
     
  3. hspalm

    Thread Starter Active Member

    Feb 17, 2010
    201
    8
    Ah that's great. Once every while, I compile and build a project for a microcontroller, program the mcu, but it doesn't work/misbehaves. Edit my code, reprogram, repeat... Just to find out the hex-file for my previous project is loaded in the programmer-software.
     
  4. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    2,805
    833
    I once bread boarded a circuit to control some servos which worked. But when I made the PCB , they all stopped.

    It was only after checking on here and a lot of debugging that I realized I had mounted the board in a different orientation and had connected the servos on reverse order.

    D'oh!
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,442
    3,361
    You would have been able to catch this if you had an oscilloscope, and another good reason to invest in one. Also that is why I do not use a DVM for testing except to read DC voltages.

    When I order a batch of LEDs I like to check their efficiency and brightness by connecting to a series resistor and 9V battery. This would have caught the blinking LEDs.
     
  6. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,388
    1,605
    Last job my new boss tasked me to do the testing on an opto coupler he developed. Just a LED and a phototransistor in a box: bare die in a ceramic header so the final product was hermetic. The third spin of protos came closest to working, at least they made it to my bench for testing, but appeared DOA. A meeting was called and in the half hour interval I did some manual probing and determined the LED was backwards: LEDs in die form come either anode up or anode down, and he used the wrong type.

    While I did give the boss the heads up on his oops I did have to announce the problem at the meeting to all. I further suggested we check the transistor before rebuilding, where my boss stated the absolute impossibility of wiring the transistor incorrectly, so I was directed not to test the transistor. Hey, just give me a tech to hold 2 more probes and in 5 minutes we'd have it checked out, but I was directed to stop so stop I did.

    Anyone care to guess what happened to the next batch?
     
  7. hspalm

    Thread Starter Active Member

    Feb 17, 2010
    201
    8
    I have an oscilloscope, but why use it when the output is so obviously pulsing? ;) Unfortunately an early test of all my LEDs would not catch this either, as I just picked it up from the "tossed"-bin.

    No what happened? :)
     
  8. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,388
    1,605
    Since you asked... of course, base and emitter were swapped.
     
Loading...