The speed of an automobile can be indicated by detecting the pulses generated by the ignition system and causing an LED to light.
This alarm circuit is based on two 555 timers. The alarm will sound your car horn if anyone opens the car door while the circuit is armed.
The circuit is drawn for measurement of acceleration from -1000 mg until +1000 mg. It can be placed in kantra’n the car and be supplied from the sheath of electric lighter. The circuit includes one indicative LED and a screen LCD.
Intro & disclaimer
For all you guys out there that want a fading dome light (aka courtesy light aka theatre lighting) without having to pay for one, you can build your own. I have attached the schematics and you can build it for a few bucks given that you don’t have any spare components lying around otherwise it can cost you absolutely nothing. Of course you can rip some parts from your TV, CD player, radio, etc., but I’m not responsible for the damage you cause this way
The way it works
I won’t bother you with technical details, but if someone is interested just let me know and I’ll explain in detail. For now just the basics. There are two stages: first one is delaying and the second one is fading. When you open the door the light turns on. You get inside and close the door, but the light stays on (delay stage) for an adjustable period of time (0-40 sec. for the values in the scheme, but you can easily modify that i.e. put a bigger capacitor) so you can see where to insert the key or do whatever you do when you get in the car, then fades away (fading stage) with an adjustable speed. If you connect the ACC wire (which is entirely optional) when you turn the key to ACC position the light turns off (actually fades) even if the delaying stage is not over (it cancels the delay stage).
The SR1 trimmer pot adjusts the delaying time (the period that the bulb is at full intensity) and you have a “witness” LED that is lit during the delaying stage; that way you can set it visually to whatever duration you like. When the first stage ends (marked by the LED not being lit anymore) enters the second stage – fading. The SR2 trimmer pot adjusts the fading time (or speed if you prefer)
The image above depicts how the dome light switch is usually connected (depending on the make and model of your car the connection may be different in which case you’ll have to figure it out).
The image below shows the schematic and the connections to the dome light switch.
Copyright 2005, kronos