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Help creating a LED flasher PCB

Discussion in 'Power Electronics' started by Neutrino, May 19, 2019.

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  1. Neutrino


    May 19, 2019
    I'm very new to circuitry and am trying to create a LED flasher for my motorcycle helmet.

    Custom printed circuit boards are not that expensive anymore, so I am hoping/planning on going that route, perhaps with a 555 chip. What I don't know is a good method of increasing the 3.7v batt voltage to the 5v the LED strips need, as well as how (which resistors, capacitors) to use with the 555 to make the LEDs flash twice at the start of every second (a 'flash-flash . . . flash-flash . . . flash-flash' kind of thing, one double-flash per second).

    If this is even possible with the 555. Is there another, better-suited chip?

    I have 5v LED strips that I can affix to my lid, and some 3.7v batteries. I have some parts from SparkFun that can almost do what I want (a 5v boost converter, connectors, etc.), but not quite. My research/circuit simulator/calculator efforts have been less than optimal. Any assistance would be greatly appreciated.
    Last edited by a moderator: May 20, 2019
  2. FuZZ1L0G1C


    Mar 25, 2014
    You could series 2x 3.7 cells to create 7.4 DC, as Vcc, then for the 5 V, modulate a higher frequency 555 with the one second 555 astable. Output should be buffered with a darlington pair transistor if total LED strip load exceeds 555 capability.
    Or use a 556 if u have in stock. 2x matched 555's in 1 package.
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Is that % V in or 5 V out? With the latter you have all you need - provided the converter can deliver the current required for the LEDs.

    I I do not recommend using a darlington here. The collector-emitter voltage drop is too high (typ. ~ 1V).
    Use a single transistor (gain of 50 or more should suffice here) or use a MOSFET. In both case the suitable type depends on the current your LEDs will draw.

    Got a question about driving LEDs?
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