hi,
just like to ask if anyone knows how to use 2 BJT transistor to set up a car headlight reminder...basically a buzzer will sound when the lights are left on but the ignition switch is off..i've tried it with a 555 timer and would like to know how it is done with the transistors.
I've been going to radio shack and buying a $3.00 piezo chirp-- then simply wire at the fuse box- one leg to the instrument panel light fuse (usually 5 amp) and the other to the wiper fuse (or any ignition hot fuse) and be done- if lights are left on-with key off- the wiper circuit provides a good enough ground to sound the chirper- if both are on (ignition and lights) then no sound, if both are off, then no sound. Has worked on every older car I have tried- and sure beats replacing a chime module for $60. If you turn off the instument lights at the dimmer switch- the chirping quits- as the OEM systems were designed.....just my thoughts.....
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Brcidd - Engineer That Does Remote Starter Installs on the side.
You could possibly use an NPN transistor on the headlight feed, and send its (-) output to the (-) side of the buzzer.
Then, you could use a PNP tranisistor on the ignition circuit, as long as it rests at ground. This could output a 12vdc signal to the (+) side of the buzzer.
You could also use one NPN and wire the base to the 12vdc headlight source, and the emitter to an ignition source that rests at ground. When the headlights are on, and the ignition is off you will get a (-) output from the collector.
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Kevin Pierson
thanks guys..yeah i found it on the website already for the transistor but still not sure how to calculate power rating, current n voltage. anyone knows any website for 555 timer mini projects...wanna check some connections to the Ic itself.