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  • JohnP460 commented on scd's instructable LED Flasher (automotive or motorcycle)4 months ago
    LED Flasher (automotive or motorcycle)

    Well, the 555 timer has a maximum input voltage of 18V, but the bike runs at 11-14.7V so it was impossible to find a proper TVS diode that had a clamping voltage of less than 18V with a working voltage of more than 15. Thus, I had to resort to regulation. I chose a simple linear 10V regulator that could handle up to 35V input. I also included a PTC resistor to protect against load dump. It should be practically bulletproof electrically. But that's not going to work for your circuit because it would never turn off (it looks like your signals are always on and blink off) - the regulated voltage would always keep a voltage drop over your emitter/base junction. I'm using an NPN to switch a SPDT relay's coil ground to provide an option for switching between normally on or off. ...Alth...see more »Well, the 555 timer has a maximum input voltage of 18V, but the bike runs at 11-14.7V so it was impossible to find a proper TVS diode that had a clamping voltage of less than 18V with a working voltage of more than 15. Thus, I had to resort to regulation. I chose a simple linear 10V regulator that could handle up to 35V input. I also included a PTC resistor to protect against load dump. It should be practically bulletproof electrically. But that's not going to work for your circuit because it would never turn off (it looks like your signals are always on and blink off) - the regulated voltage would always keep a voltage drop over your emitter/base junction. I'm using an NPN to switch a SPDT relay's coil ground to provide an option for switching between normally on or off. ...Although, I suppose you could add in a small transistor to switch the power one at the proper level. I whipped up a schematic of the protection/regulation circuit in MSpaint for you:

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  • JohnP460 commented on scd's instructable LED Flasher (automotive or motorcycle)5 months ago
    LED Flasher (automotive or motorcycle)

    Is this still working long term on your motorcycle? I'm designing a similar circuit, but I was going to use a voltage regulator, PTC resistor, and TVS diode to protect the 555 against voltage fluctations and static which can be pretty extreme, especially on an old motorcycle (I have an old BMW airhead). Is the 555 timer robust enough to handle that?

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