ultrasonic obstacle detection

[matthew K]

hi, my project requires me to build a circuit to detect obstacle a few meters ahead. Can any1 tell me how to start building my circuit. anything to look into before start? i'm using ultrasonic sensor MA40S4R/S btw. TQ

 

[Sceadwian]

Well the sensor isn't going to do you any good at all without a transducer. You simple generate a short pulse train on the transducer, then time how long it takes to hear the first echo back. Using time and knowing what the speed of sound is you can determine how far away the first object to return an echo was.

You said a few meters, but what's your short range?

 

[matthew K]

i don't get what u mean by generate pulse on the transducer? is it the transmitter generate ultrasonic sound wave and reflected back on the receiver? then the time taken for the wave return is used to calculate the distance? the short range is not specified in my project. TQ really appreciate ur reply

 

[Mr RB]

Have a look at this ultrasonic sensor unit; Pololu - Maxbotix LV-MaxSonar-EZ0 Sonar Range Finder MB1000

It's like a 1" cube size, $27 and detects from 0 to 6.2 metres automatically. Low power required, auto beam adjustment, AND has 3 outputs that all work at once;
* Serial output: asynchronous, logic-level, inverted, 9600 bps 8N1
* Analog output: (Vcc/512) / inch (10 mV/inch when input voltage Vcc = 5 V)
* Pulse width output: 147 μs/inch

 

[Sceadwian]

Yes that's what I mean matthew. Generally the transmitter burst is quiet short, only a handful of cycle at the output frequency, the receiver is turned on immediately after the output pulse ends. The module Mr RB mentioned is relatively expensive but looks very nice, I'd recommend them over doing it yourself if you have the budget and part of the project isn't designing the sensor module itself.