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Wiring 555 Timer as Signal Flasher Honda CT90?

Discussion in 'Electronic Basics' started by Gerryo, Aug 29, 2007.

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  1. Gerryo

    Gerryo Guest

    Hi Folks:

    I need a bit of help.
    I want to use a 555 or similar timer to activate my signal lights on
    my trail bike.
    Why do I want to change the original system? I have plans to go to all
    LED signals and brake lights so this circuit board is the first step
    and the original thermal flasher is not that reliable and does not
    work well with low current draw of the LED's.

    REQUIREMENTS: I need the circuit board to be a plug in unit so I do
    not have to modify the bike wiring to be able to use this board. Note:
    This turn signal circuit is always powered by the ignition Switch and
    6VDC 5.5AH battery and I don't want to modify this feature if at all
    possible..

    ORIGINAL SETUP:The original turn signal circuit used a thermal flasher
    and did not present a problem as it was in series with the relatively
    high current indicator bulbs and was not activated until the manual
    signal switch was in L or R position and it gave the flasher time to
    heat up and start flashing.


    PROBLEM: The replacement circuit ( see this link -
    http://gerryo.wordpress.com/2007/08/29/555-relay-switching-circuit/ -
    to the diagram in my blog) works well with the single exception the
    relay and the 555 are always cycling at a 1 hertz rate even when the
    signal lights are in the OFF position. This is unecessary use of
    limited battery power and will wear the components out quickly. Anyone
    have any ideas how I could modify the circuit to intially cycle the
    relay for maximum 1 minute when manual L or R is selected,then have
    the relay and timer turn off until the L or R switch is selected
    again? Disregard the horizontal line passing through the timer this
    is a scan error.

    POSSIBLE SOLUTION: I was thinking a 556 dual timer as well as using
    the Normally Closed position on the relay contacts might be useful in
    this situation but I am at a loss on how to connect it. Any ideas or
    advice would be appreciated.

    Cheers...Gerry
     
  2. Guest

    I would approach this problem with a "sensing" circuit. Generally,
    you can keep your flashing circuit just like it is. Just sense the
    turn signal switch being switched to L or R with a PNP transistor
    circuit tied to the circuit board output. When the switch is turned
    to either L or R, it ties the circuit board output to ground via the
    turn signal lamps. That could turn on a PNP transistor. The
    transistor circuit can then turn the 555 timer on and off.

    Sorry. I don't have the time to design the whole circuit, but
    hopefully this will give you a direction.

    BRW
     
  3. Jamie

    Jamie Guest

    You don't need the relay.
    remove the relay, connect the Collector of the TIP120 to your +6 volts.
    lift the Emmitter from ground and use that the feed the circuit for
    your LED's
    You may want to consider a Power P-Channel Fet in place with that
    transistor. if you get a Logic type, the turn on resistance is very low
    and thus will not heat up so much..
     
  4. default

    default Guest

    Well if the relay isn't switching current it should last awhile or a
    few million cycles anyway.

    I had a need for a flasher that would work the lights on my bike after
    I put leds in the front turn signals. I designed one around a mosfet
    with a 10 UF cap to hold the mosfet on while the mosfet was shorted -
    no connection to the ingnition source and only two wires in series
    with the turn signals.

    Only about 7 parts and works like a champ - will post the schematic on
    alt.binaries.schematics.electronic if you want.. No moving parts -
    works from 11 volts to 15 volts and from 100 ma load to 10+ amps load
    with no change in flash rate. Two transistors one zener diode and a
    few resistors and one cap.
     
  5. Ross Herbert

    Ross Herbert Guest

    It will be far simpler and cheaper in the long run to simply replace
    the current flasher module with one designed for LEDs. Once you start
    designing your own, pleasurable as it may be, you are going to run
    into the major problem of 'packaging'. This aspect on a trail bike
    will take some ingenious diy tricks if the electronics are to be kept
    safe and secure from shock and the outdoor environment. The socket for
    the flasher is already there so all the problems are solved simply by
    replacement.
     
  6. Gerryo

    Gerryo Guest

    30 August 2007 8:17 PM

    Thank-you very much for your replies. It has given me a few avenues to
    explore.

    Cheers...Gerry
     
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