David, that's an interesting suggestion. I am a bit busy for the next few weeks to try it, but I think the ability to calculate position would be extremely useful even for Earth-bound robots. I have several sets of very low-cost ultrasonic transducers, and I'm a 'dab hand' at 38KHz modulation (I've just made a Nikon IR remote), so lashing something up with a couple of Arduino's should be straightforward.

Thank you very much for sharing the idea, you've stimulated my creative juices :-)

Garry

PS - You have an amazing web site. Wonderful!

I have a sillyscope, and I've been meaning to do that for months!
I need to get my work done 1st and avoid distractions like this :-(

I tend to use an Arduino for signals. It is extremly easy to make a 38KHz signal using the hardware timers, and I can always stick a cheap Darlington transistor on the output. I need to do that anyway if I am going to use it, so no big problem. It's just lack of time!

GB-)

I agree, at 5V driving the transducer is likely just as good from the Arduino directly. There impedance is about 1K at 40KHz. I wasn't thinking of current, but the voltage.

These are the sensors I have:
http://www.rapidonline.com/Electronic-Components/Sensors/Ultrasonic-Sensors/Ultrasonic-transducers/30210

and they are measured at 10V (maximum 20V RMS), so I was thinking of using a 9V battery, and a transistor (or CMOS buffer) to drive at a higher voltage to get a stronger signal out :-)

That isn't necessary for an experiment, but I want to see how far I could reliably detect with a larger voltage swing (I'd like to try in the local schools sports hall).

GB-)

My electronics is mostly self-taught too, so I have (many) holes. I use the "Art of Electronics" a lot, which is brilliant.

The only way to amplify the return signal I feel I understand is to use an Op Amp and a few resistors to set gain.
How you do it?

The ADC inputs of the Arduino are so slow as to be virtually useless (sampling at under 10KHz), so I need to drive the received signal above 2.5V so that I can sample with a digital input.

GB-)