fast Ultrasonic < 20ms

hi guys! i need a very fast ultrasonic sensor which will keep up to the 60fps of my camera.

what about the PARRALAX Ping))) ? http://www.parallax.com/Store/Sensors/ObjectDetection/tabid/176/CategoryID/51/List/0/SortField/0/Level/a/ProductID/92/Default.aspx

will this baby make 20ms or did i misinterpret the sheet? i'm also open for other suggestions!

cheers :)

will this baby make 20ms or did i misinterpret the sheet?

Even if it does (a round-trip distance of about 6.8 metres, consistent with the quoted maximum range), 20ms is only 50Hz.

Thx for the quick answer! Yes, 20ms ~ 50fps. This is fast enough. And I want to track movement between 10 and 100 cm.

This Tutorial on the playground says the Ping)))s signal needs 29µs / cm = 2900µs / 100 cm = 5800µs (6ms) to return. but there will be additional time for sensor reading and so on. There is also a delay(100); in the syntax, i wonder why?

At the moment I'm using the SRF02, which needs a delay of at least 70ms in order to work correctly. I just want to make shure that the new sensor is really that fast before I buy it.

The ping)))s datasheet says:

Host Device Input Trigger Pulse tOUT 5 [ch956]s typical Echo Holdoff tHOLDOFF 750 [ch956]s Burst Frequency tBURST 200 [ch956]s @ 40 kHz Echo Return Pulse Minimum tIN-MIN 115 [ch956]s Echo Return Pulse Maximum tIN-MAX 18.5 ms Delay before next measurement 200 [ch956]s

All together that makes about 20ms or did I forget something? I don't know that much about electronics :-/

cheers

Very little to do with electronics, a lot to do with clutter. Imagine you fire an ultrasound "ping" at an object that's 50cm away. After 1/340th of a second (just under 3ms) you get a return echo, so you immediately fire off a second pulse. However, there was another object that was 75cm away which reflected some of the first pulse. The receiver now receives this echo of the first pulse, and thinks it an object nearby, just 25cm away. See the problem? Your pulse repetition rate is set by the maximum range of your sensor - you have to wait until an echo cannot be distinguished as a valid return before sending off the next pulse.