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A question related to the LED Dimmer circuit of 05/29/07

  1. Jun 30, 2007 #1
    I want to replace a single flashing red LED on my motorcycle alarm with something more ominous to ward away potential hooligans ;) I've searched for flashing & pulsing and ramping LED circuits using Google and came across this forum, so hopefully someone here can help me :)

    What I would like to have is a set of several high intensity LEDs wired in series (perhaps 8 in total). I want these LEDs to turn ON and OFF in a ramping manner with a frequency of about 1.5 to 2 Hz, in other words, the intensity of the LEDs will increase to maximum in a period of about 1 sec, then hold at maximum intensity for maybe 0.1 sec before decreasing back down in another 1 sec. Ideally, I would like the LEDs not to turn off completely in the trough of the ramp, but stay glowing slightly at maybe 10% of maximum intensity, so there would always be some light emanating from the LEDs when the alarm is on.

    The circuit discussed in the 05/29/07 thread ramped at a much slower rate than what I want, so I'm looking for some feedback in terms of a modification to this circuit to change the frequency and minimum intensity, or a link to a circuit that does what I'm looking for...

    One potential complication with my situation will be powering this ramping circuit from the alarm currently on the bike. As I said earlier, the alarm has a single red flashing LED, and although I haven't tested the output, I believe the voltage and amperage supplies by the alarm box to this LED would be typical of what is required for a LED (ie: ~3 V & 20 mA). Since the power source that is available is not always on, I will have to either modify whatever ramping circuit I end up using, or modify the alarm itself to bypass whatever is making the existing red LED flash:confused:

    As an added bonus, if I get this to work.... I would like to eventually combine sound with the ramping/pulsing LEDs, something like a pulsing humming/droning sound that also increases in intensity at the same rate as the LEDs. The best I can describe the sound would be something akin to the sound of a bullfrog, but a little slower in frequency. I think I've seen something like this in a Sci-Fi movie, when some unknown alien craft lands on earth and you get that ominous throbbing light and droning sound...

    Hope I can get some feedback, at least on the LED circuit for now. Also, kepp in mind that I am a Mech Eng type, so please speak slowly :uhh:

    Thanks !

  2. jcsd
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