Let's Make Robots!

Looking for a cheap long range distance sensor.


Would anybody know of a cheap long range distance sensor? 

Something with a max distance of 2.5 to 3 meters. It would be for my nitro rc car, I dont totally trust my radio system so a distance activated fail safe would be really reassuring!  

Accuracy isn't ran issue, but price is. 


Thank you in advance! 


Well, found these http://www.futurlec.com/Ultrasonic_Sensors.shtml , but ... haven't got a clue how to wire them up, 

if its kinda like the ones on a SRF005 I'm going to need a fair few components. Any easier way? Maybe by replacing the ones on a prebuilt module to upgrade the sensing distance ?