Attention flashers from LED flashlights ?

Discussion in 'Electrical' started by Luka, Sep 17, 2009.

  1. Luka

    Luka Member

    I like the idea of using LED flashlights on the front of the bike.

    I have been planning on using two of them.

    But a couple of other threads here have gotten me to thinking further.

    I'll assume that it is possible to pull the battery packs out of the flashlights, and run a wire from a single 4.5 volt source, to power both lights.

    Not beyond my capabilities.

    But what I am wondering is, is there a way to do this so that one light is on, the other is off... Then the other is on and the first is off. Continuously flashing back and forth, like that ?

    Without having to build some huge/complicated electrical 'project'. (Diodes and rectifiers and bridges, oh my !)

  2. HoughMade

    HoughMade Guest

    Here is the simplest of simple turn signal circuits. Just change the battery to a 4.5v source and whatever LEDs compatible with 4.5V you have.

    Attached Files:

  3. Luka

    Luka Member

    Thank you, but I know how to wire a turn signal circuit.

    I am not talking about turn signals. I want continuously flashing lights, for attention sake. And not both on, both off. (I could easily do that, as well, with a simple flasher unit.) I want them to flash on one side, then the other, then the first, etc... Constantly, with no effort on my part other than turning it on in the first place.

    I don't want to have to keep a hand on a turn signal switch, switching it back and forth, back and forth, all the time... LOL (Besides, if I were going to do it that way, I wouldn't even need the flasher unit. Just a SPDT switch.)
  4. HoughMade

    HoughMade Guest

    Oh, OK- my bad....good luck- can't help you on that one.
  5. Luka

    Luka Member

    Yikes !

    Just re-read what I wrote and it didn't come across the way I intended.

    Sorry about the seeming brusqeness.
  6. fetor56

    fetor56 Guest

    Ask an Auto Electrician....their must be a really simple way of doing it with minimal electronics.
    Google it to & please post your results.
  7. Luka

    Luka Member

    Well, I have done about an hour and a half research, and this is what I have found...

    These are sites which contain circuit diagrams for several different ways to build this yourself: LED

    This last site is my favorite. The link there, will download a PDF file, with several diagrams for different things.

    Here is the diagram out of that PDF, for the led alternating flasher. (I have done a screen capture, then saved it in paint shop pro.)

    This cannot be adapted to two flashlights, because it is the particular LEDs in the diagram and instructions, that make it possible. But it would at least put alternating flashing LEDs at both side of your handlebars , or somewhere on the back.


    Here is a factory made flasher. It flashes back and forth, as I had hoped. But it is only 6 inches across.

    I am thinking this could be taken apart, and the guts used to power two led flashlights, instead. Or... Maybe the flashlights could just be tied into this, and have all three lights flashing...

    Here is a different idea. These are pretty cheap. You could get three of these, spread them across some sort of mount. Set the outside two, to flash fast, and the middle one to flash slow, or versey-visey. Etc...

    I am including this one simply because I think it is worth mentioning. This is just a light. Again, about 6 inches across. But it has 28 super bright LED's in it. Can be seen from a long way away. And fast flashes or steady on.

    Attached Files:

    Last edited: Sep 17, 2009
  8. fetor56

    fetor56 Guest

    Good job Luka. :grin5:
  9. loquin

    loquin Active Member

    Something like the circuit below should work.

    When power is applied, current flows through the normally closed relay contact through R2 to charge the capacitor. Once the capacitor voltage reaches the relay pull-in voltage (about 3.4V) the relay contacts switch state.

    Now, the capacitor discharges through the relay coil until the voltage drops to the drop-out voltage (about .5V) Then, the relay opens, and the cycle begins again.

    The trim-pot variable resistor was added to 'balance' the time between charge and discharge cycles. by providing a small amount of 'make-up' current to the capacitor, it will act to 'stretch' the discharge time a bit. It should initially be set to about 2500 ohms. (about half way.)

    The diode is present to absorb any reverse voltage spike when the magnetic field in the coil collapses, to protect the capacitor and the relay contacts.

    Note - I haven't bread-boarded this exact circuit. (I have done so with virtually the same circuit, but with different voltages/relays, though.) Some experimentation will be needed. If the timer flashes too fast, you'll need to add some capacitance in parallel with C1. If it's too slow, replace C1 with a smaller cap. With these values of R and C, it should switch at about a 1.5 cycles per second rate. It might turn out that R1 and R2 wouldn't be needed at all. (In which case, remove R1 entirely, and run a wire in place of R2.)

    The only critical part in this circuit is the relay. It's about $3.50 (unit price) from digikey.
    The flasher circuit will draw about 20 ma from the battery pack, plus the current to power the LEDs. Obviously, you'll also want a switch between the battery positive terminal and the circuit.

    Just about everything else you could find at radio shack. Of course, you could order them at the same time as the relay, too.

    Attached Files:

    Last edited: Sep 21, 2009
  10. DetonatorTuning

    DetonatorTuning Active Member

    what you are describing, in any colored or even clear lense is called "wig-wag" and illegal ( i think ) in our state for other than police and emergency response.

    is that correct Houghmade ?

  11. Luka

    Luka Member

    Looks like french to me.

  12. Luka

    Luka Member

    I thought that was the case, as well.

    But I have seen motorcycles here, with the 'wig-wag' lights. And even a flashing headlight.

    Guess I'd better figure out where to find what the law is, in washington state.

    Thank you.
  13. loquin

    loquin Active Member

    You're correct about the alternately flashing lights. You could probably be ticketed for it. I came up with the first version of this circuit for an uncle, who was a volunteer fireman in VA. He was only entitled to use the lights wired up as a wigwag flasher when he was responding to a fire.
  14. Scotchmo

    Scotchmo Member

    Use a switch to supply power to two bulbs and an automotive flasher. The flasher powers an automotive NC/NO relay. One light is grounded through the NC side of the relay. The other light is grounded through the NO side of the relay. The turn signal flasher powers the relay on and off which in turn alternates the two lights hooked to the relay. It would work with LEDs or incandescent lights.
  15. Luka

    Luka Member

    That sounds easy enough !


    Is this an nc/no relay, like you suggest ?


    This is a turn signal relay. Some have three tabs.


    Could you give me a 'coloring book easy' picture, of what gets connected, where ?

    Attached Files:

  16. Scotchmo

    Scotchmo Member

    That relay is incorrect. It is a SP (NO) relay. You need a SPDT (NO/NC) relay. Try this or one like it:

    Go to and look for part # 75602

    Many light housings are grounded so it is better to use the relay to control the +12v feed rather than the ground connection that I first proposed.

    I included a diagram that should work. There will be an additional terminal (87a) on the SPDT relay.

    You could run bulb 1 directly off the flasher as shown in the second diagram below. That would provide a larger load that some flashers might require. Terminal 87 would not even be used.

    Attached Files:

    Last edited: Sep 19, 2009
  17. Luka

    Luka Member

    Great !!

    Thank you very much.

    One last question:

    Is this the same animal ? (Looks like it to me.)

    It's part #RY115


    I'm hoping this is right, because I can just go pick one up at the local schucks auto parts place.

    It has all the same numbers on it.

    Only problem I can see is that the numbers may be on the side, but I don't think the numbers are on the bottom, next to each individual terminal.

    Can you tell from that pic, what the numbers would be on each terminal ?

    I hate being a pain in the butt. I hope this isn't too much hassle.

    Attached Files:

  18. Scotchmo

    Scotchmo Member

    That relay will work.
  19. Luka

    Luka Member

    Very cool.

    I just might actually try this !!


    Can you tell what number goes to each terminal on the bottom ?

    And thank you very much again.
  20. Scotchmo

    Scotchmo Member

    I can't see the numbers on the bottom. It should be labeled or come with documentation. If not, you can figure it out using an ohmmeter.

    Some automotive flashers require a higher minimum load than that SPDT relay or LED will provide. If you use that flasher you may have to put a resistor across 85 and 86 of the relay.

    If you use automotive 1156 type bulbs and wire it according to the second diagram, any flasher should work. Otherwise use a flasher designed for LEDs or a load resistor.
    Last edited by a moderator: Dec 15, 2015