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    led flasher circuit

    good morning everybody i found this circuit on board of led flasher and i was trying to know the rference but i can't
    please can you help me to know it and how it works
    all regardsClick image for larger version. 

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    Last edited by kik; 14th June 2013 at 06:15.

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    Re: unknown circuit for led flasher

    The photo is fuzzy but it looks like a stack of several led's, controlled from a central unit.

    A common IC used for this is the 3914 bargraph/dot display driver. It has ten outputs which turn off or on in sequence, based on volt level at the input terminal.

    An internet search will provide abundant information about such circuits.



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    Re: unknown circuit for led flasher

    thank you sir for the replly but its not lm3914 bargraph
    its a IC that drive 4 leds to be blinked with 4 transistor, 1 capacitor and 2 resistor
    all my best regaards



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    Re: unknown circuit for led flasher

    It isn't an IC you could buy in a store, it's a small PCB with an IC mounted on it under the black epoxy. It could be anything, I have a similar one here that flashes four LED chains but what you describe as transistors are SCRs.

    Brian.
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    Re: unknown circuit for led flasher

    yes sir it is using for falshing leds and that's exactly what i need can you help me to know how can i realize it??
    because i want to build a small led flasher like that



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    Re: unknown circuit for led flasher

    It is a COB led flasher. COB = Chip on board. See if you can buy COB type LED flasher.



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    Re: unknown circuit for led flasher

    yes sir it is using for falshing leds and that's exactly what i need can you help me to know how can i realize it??
    because i want to build a small led flasher like that

    - - - Updated - - -

    and can you help me to know the name of this COB??

    - - - Updated - - -

    yes sir but can you help to know the name or reference for this COB????



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    Re: unknown circuit for led flasher

    The actual working of the COB cannot be determined. The leds may show different patterns. If the chip on COB is a micro-controlller then it is sure that it is programmed to display different patterns. If you want to realize the same circuit using a microcontroller then you can do it easily. Choose any microcontroller with 8 pins for LED and then code can be written to generate different led sequence or patterns.

    http://www.quasarelectronics.co.uk/I...flasher-module

    http://www.indiamart.com/anykits/mini-kits.html
    Last edited by jayanth.devarayanadurga; 6th July 2013 at 15:36.



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    Re: unknown circuit for led flasher

    and can you help me to know how can i wire 20 leds with this COB using transitor??

    - - - Updated - - -

    really thank you so much, you and Betwixt because you helping me and i'm looking that someone help me on that
    thank you very much



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    Re: unknown circuit for led flasher

    You mean 5 to 20 connections. Each COM pin can drive only one led or one transistor. You can put 5 leds in parallel at the collector of each transistor and drive the transistor from COB o/p pins. The result is instead on 1 led lighting, 5 leds light up.



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    Re: unknown circuit for led flasher

    i want to driave ecah 5 led with one pin of this COB and the 5 leds will be on series because i want to have the same current on each pin to have a good lighting



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    Re: unknown circuit for led flasher

    Calculate the voltage drop across each led in series. Voltage supplied to transistor circuit should be a little above this. Ic will be the current through each led. Fix Ic to 10 or 15 mA.



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    Re: unknown circuit for led flasher

    so there is no way to have some led in series for exemple we can use npn transistor for that??



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    Re: unknown circuit for led flasher

    The method I gave is for 5 leds in series per tarnsistor. If one led fails then all the 5 leds will be off. You can use any transistor either npn or pnp as it is used as a switching device.



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    Re: unknown circuit for led flasher

    can you help me at least to know how can i build the flasher circuit like that?? or can i find it on electronics shop??

    - - - Updated - - -

    because i did it with transistor and it doesn't work with me??
    do i did something wrong??



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    Re: unknown circuit for led flasher

    Post your circuit showing one transistor driving 5 leds.



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    Re: unknown circuit for led flasher

    ok
    this is what i did



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    Re: unknown circuit for led flasher

    Which transistor did you use. What is the value of IB (Base Current).



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    Re: unknown circuit for led flasher

    its npn transistor 2N3904 but in the original PCB i found it attached wit PCR606



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    Re: unknown circuit for led flasher

    I doubt you will get it to work. The PCR606 is an SCR and the COB is probably producing trigger pulses rather than a continuous signal. In any case, you would want to connect the LEDs in the collector of the transistor because at the momant, to turn the transistor on you have to put (0.6 + total Vf of all the LEDs) volts on it's base and that is almost certainly more than the COB can produce. Try moving the LED's to the colector and adding a resistor, I suggest 2,200 Ohms between the base and the COB output.

    Usually, PCR606 is used to drive LEDs which are fed from AC or rectified but not smoothed DC. It relies on the voltage dropping to zero at each half cycle to turn the PCR606 off.

    Brian.
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