[list]i am doing a project on automatic braking
system in cars. my idea is to put a sensor in
the front of the car and connect to the brake system.for example if a car is in front of u and u didn't see that.befor u hit the car the sensor will detect and automatically brake.

01191

Another more reliable but by no means easy way of doing it is to use lasers. This would increase the range, but you'd have to be careful about directions, focusing etc.

Basically what you need to do is, reliably, transmit some form of signal out the front of your car on the bumper (ultra sonic, sonar, light, whatever) and then time how long it takes to receive the signal again. Poor mans radar basically! You'd have to do some very impressive tests and calibrations however and have alot of complex brains in your circuits!
You would need to take into account your speed, the weather conditions, road surface. You'd also have to find a way of smoothly applying the brakes! Not an easy project!!! But it is possible. The US military tried employing similar techniques back in the early 90's to make automated vehicles for the battle field. And Mercedes uses automatic cruise control on their more hi end models. You could try contacting Mrecedes HQ technical department or have a snout about on the web, see if you can find out more about it, may help.

Originally Posted by mozikluv

what you need is an ultrasonic proximity sensor, but this has a limitation as to effecive distance. i have that circuit installed on my wife's car. it help her when she parks her car. women are sometimes not good in judging distance :wink:

Where did you get that / what car is that on? That would help her quite a bit.

Originally Posted by crust

Where did you get that / what car is that on? That would help her quite a bit.

You can buy them as addons at any car accessory shop, it's a very common item, some manufacturers even fit them as standard.