Newbie need help with LED semiconductor strobe circuit

Discussion in 'The Projects Forum' started by customsportbike, Feb 9, 2010.

  1. customsportbike

    Thread Starter New Member

    Feb 3, 2010
    4
    0
    Hi everybody. I'm pretty new at electronics. I am an apprentice electrician so I understand most of whats been said here.

    I have been doing research on a strobe circuit that could flash one group of leds 3 or 4 times then flash a second group the same amount of time. I have attempted to use the 555 timer with a 4017 decade counter. It will work, but I found this other circuit that does the same thing but without the chips.

    I have been trying to re-produce this circuit but can't seem to do it. I think it has a semiconductor installed. I have attached some pictures of the circuit I'm trying to re produce. On the back side of the circuit board there was a black epoxy blob that I removed to figure out whats happening.

    Inside the blob there is a tiny square something that does conduct but can't get an ohm reading through it.

    It seems to be a really simple circuit except for the black blob part. Any ideas?
    Lights flash simultaneously or Lights flash one after the other

    I put the circuit operating on youtube:
    http://www.youtube.com/watch?v=MiFlF2FgzOA

    This circuit uses:
    (2) S8550 transistors,
    100uF cap,
    (2) diodes,
    I think one zener diode,
    electrolytic cap it say 104 on it,
    (2) 1.6k resistors connected to transistors,
    560 ohm res. located next to cap,
    and a 5.6k resistor next to the 2 diodes.
     
    Last edited: Feb 9, 2010
  2. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
    1,758
    98
    That epoxy blob was a COB (Chip on Board)
    Removing it killed it. It could have contained almost anything and it's usually a custom IC.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Yeah, prying the epoxy blob off wasn't a great idea.

    If you want to get away from using multiple ICs for such projects, you should have a look at microcontrollers aka uC's, MCU's. The learning curve can be steep in the beginning, but once you "get the hang of it", you can do a heck of a lot with a very low component count.
     
  4. customsportbike

    Thread Starter New Member

    Feb 3, 2010
    4
    0
    Yeah it was an ic, fortunatly I have others. I am gonna reseach micro controllers a bit and see what I can make of it. Other wise I'll stick with the 555 timer and 4017 decade counter
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Are you just trying to flash an LED, or are you going for a pattern?
     
  6. customsportbike

    Thread Starter New Member

    Feb 3, 2010
    4
    0
    Basic pattern, but using multiple Led's (4 red 2 white 2 blue) and a 9v battery.

    Red leds to flash 4 times: R1 R2 flash the same time then R3 R4
    Blue to flash 4 times: B1 then B2
    White to flash once: W1 then W2 wig wag style headlights

    That's why I think I should go with a 555 and a 4017.

    I would like to use a pic chip but I know nothing about programming right now, and because I'm in school doing my elec. apprenticeship I'm bogged down with studying and homework and don't think I can fit anything else in brain right now.
    Maybe after school I'll research into programming.
     
  7. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
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