Help with LED strobe circuit

Discussion in 'The Projects Forum' started by westva1, Jan 14, 2007.

  1. westva1

    Thread Starter New Member

    Jan 6, 2007
    9
    0
    I've been working on various circuits to make LEDs (12 volt clusters of them) strobe. I looked at a commercial unit. It does not use a 555 because pin 1 is the 12v voltage in on the 8 pin IC. Pins 2 and three have a 64K resistor across them. Pin 4 is not connected. The output (PIN 7) looks like it connects to one side of a transistor. The center pin and I assume it the BASE connects directly to the output (12 volts). The circuit will drive up to 100 leds it says. It strobes (4 times in a second) pauses and repeats. Any help on what the IC number and transistor type would be appreciated.
     
  2. westva1

    Thread Starter New Member

    Jan 6, 2007
    9
    0
    Almost forgot...pin 5 goes to a 100 ohm 3/4 watt resistor to ground. Circuit also has 2 diodes and a 10ufd cap.
     
  3. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
  4. westva1

    Thread Starter New Member

    Jan 6, 2007
    9
    0
    Actually I have diagrams similiar to those. The circuit I need is attached. I wrote down the parts I could see, but the IC and looks like transistor numbers are unknown. Does anyone know what the two unknowns could possibly be? Pin 1 on the IC is + in. Pins 4, 6 and 8 are not connected. The circuit can be connected to a max. of 100 12 volt Ultra Bright LEDS. It pulses 4 times a second, pauses and keeps repeating. Its used on emergency LED lighting for volunteer firemen, police, etc.
     
  5. westva1

    Thread Starter New Member

    Jan 6, 2007
    9
    0
    I attached the circuit "unknown.jpg" several days ago with no response. Sure would be glad if someone could steer me in the right direction as for the two unknown parts in the diagram.
     
  6. Distort10n

    Active Member

    Dec 25, 2006
    429
    1
    If you looked at the IC in the commercial unit, what topside markings did it have?
     
  7. westva1

    Thread Starter New Member

    Jan 6, 2007
    9
    0
    The IC has EX301 on it...no such unit. And the transistor has A102D on it.
     
  8. Distort10n

    Active Member

    Dec 25, 2006
    429
    1
    Nope, not a 555 or a monostable multivibrator.
     
  9. westva1

    Thread Starter New Member

    Jan 6, 2007
    9
    0
    Does anyone know what 8 pin IC is in the "unknown.jpg" I attached earlier? Its a really neat circuit. Can't find an IC with that number on it and NONE that have pin 1 as the 12+ in.
     
  10. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Your circuit depicts D2 with a capacitor symbol.
     
  11. westva1

    Thread Starter New Member

    Jan 6, 2007
    9
    0
    D2 is a diode (small glass) and looks like a IN60A. I just drew it fast. I'm just trying to figure out what the IC and transistor could be. Can not find any 8 pin ICs that have pin 1 as the + voltage.
     
  12. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Which side is anode and which is cathode?
     
  13. westva1

    Thread Starter New Member

    Jan 6, 2007
    9
    0
    the negative side is connected to pin 5 of IC and to R2. The + side connects to the + side of C1 and to the power in from the main diode.
     
  14. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Why can't pin 5 be V+?
     
  15. lightingguy32

    New Member

    Jan 9, 2008
    1
    0
    Any body know how to make a strobe circuit (oscillator rather) with two NPN transistors. I remember doing this my self a while back with 2-2N3904 Transistors, two resistors, and two capacitors, but I can't remember the lay out. It adjusts the strobe rate by changing the capacitor values and resistor values.
     
  16. 630R63

    New Member

    Jan 23, 2008
    1
    0
    Here you go!!!
     
  17. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Hmm - thingmaker3 brings up a good point - seems like this is a "house-numbered" IC to make it more difficult to determine the actual part number.

    It's entirely possible that they also put the pin 1 indicator on the wrong end of the IC to make it even tougher ;)

    See what you get when you look for 8-pin IC's that have Vcc on pin 5.
     
  18. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    It's probably "in-house" markings they have, but why would you need these exact components?
    If you just wanna build something for personal use (i.e. not for profit), just use another circuit.

    Here is a circuit I made some years ago for a volunteer firefighters vehicle - not exactly what you want, but it's in use a couple of places around the globe and proven to work reliably.

    Use only for non profit though!
     
  19. ganthony

    New Member

    Feb 4, 2008
    1
    0
    On Soren's emergency vehicle schematic, is there any limit to what kind of leds you use; is it possible that some hi-powered leds need too much power? Because I was looking at leds that use 3.6 volts and 300mA forward current. If that is too big, what is the max that i can use?

    Thanks for your help
     
  20. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    The TIP122 Darlingtons that Soren specified are good for up to roughly 4A.
    If you need more than 4A, TIP140, TIP141, or TIP142 are good for up to 10A continuous. In this application you could probably get up to 12A from TIP14x's. Be sure to use heat sinks on them to avoid overheating.
     
Loading...