seatbelt warning circuit

[Nelson Mokhitli]

im about to design a project of a seatbelt alarm/warning circuit, so could you please help me with a circuit diagram that i will modify by myself.

 

[ADWSystems]

Are you looking to build something like this:

Sunshine Kids Belt Guard - Sunshine Kids - Babies "R" Us

 

[mbarazeen]

its much simple, tell about your level of experience / education in digital electronics. if you will understand it should be as follows using simple switches.

seat belt alarm / light should be activated when some one sits on the seat and the belt is not used.
so you have to have two switches one will turn on (close) when some one sit on the seat. and the other will be on the belt lock mechanism & will be normally on (closed) when the belt is not attached.

connect both in series with the siren / lamp and it will work, there are ways to do it using digital too.

 

[Gary B]

I thought all cars came with the things built in since the ‘80s. Perhaps I’m just thinking about the front seats.

I recommend the 2-switch method but, I would use only a single wire. Body ground comes into the first switch under the seat through its NO contact. It is passed to the NC switch contacts in the seat buckle then to a 12 volt relay and a battery source controlled by the ignition switch. If there is enough weight on the seat to activate the first switch and the engine is running, then the relay will pull in and alarm will sound unless the seatbelt is fastened.

Use the relay contacts to control whatever alerting devices you like including the idiot light in the instrument panel.

 

[Rbeckett]

Nelson, Not trying to dissuade or discourage but be carefull modifying the vehicles light and electrical circuits. Done a few mods over the years, and was less than impressed by the end result. What works well in a lab environmet/on paper doesnt do quite as well on the road. Plus the seat belt system is a federally mandated safety system that is probably off limits or at least taboo. Some late model cars use a small explosive charge to suck up the belt in a collision and you would not want to trigger or compromise a system like that. It is very expensive to replace those parts and recertify the proper operation if something happens. Sorry...
Bob