Yes, the units I analyzed were car parking sensors. They are cheap now, around USD25.00 an unit with 4 transducers, 2m range and waterproof . Here in Brazil it would cost more than that to buy just the transducers. Isaac Em 23/10/2013 02:52, Luis Moreira escreveu: > It's probably the way they do it on the automotive industry. > Regards > Luis > On 23 Oct 2013 00:10, "Isaac Marino Bavaresco" > wrote: > >> It is possible to use just one transducer. I have seen >> transformer-coupled systems that works this way. I think it is a little >> trickier to get right but also more elegant. >> >> >> Em 22/10/2013 17:41, Brooke Clarke escreveu: >>> Hi Lindy: >>> >>> These are raw transducers which are much harder to use than range finde= r >> modules. >>> for example: >>> https://solarbotics.com/product/40300/ >>> or >>> https://solarbotics.com/product/40310/ >>> >>> Search eBay for ultrasonic range finder. >>> >>> To roll your own you need to (1) drive the transducer with a short puls= e >> of 40 kHz drive and then use a second >>> transducer as a receiver with a narrow band amplifier centered at 40 kH= z >> then envelope detect that. The two different >>> model numbers you mention have different bandwidths which determines th= e >> rise and fall time of the pulse they can >>> generate. The range finder modules have done all that for you and >> probably for less money. >> -- >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .