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[Reply #15 on:]

I just ordered a ultrasonic range finder, myself. So I can start my robot project.

[Reply #16 on:]

thought about making your own? its a 6$ per pair part with some simple electronics

Everything I have seen about homebrewing your own "ping" style sensor tends to reccommend having both a frequency generator and an oscilloscope in order to properly "tune" the emitter (for the frequency of the transducer); the same for the receiver (for optimum accuracy and distance).

I am sure you could "eyeball" it with minimal test equipment, but I don't know how well it would work...

Is there another method?

 :-?

[Reply #17 on:]

getting it to resonate "right" is easy.
it is like worrying about the sound of a tuning fork, no matter how you hit it, it resonates at it's natural frequency.
"about 40 kHz" is all you need to know to work effectively with them.

I tried a long time to produce varying frequency chirps using piezo, to no avail. what you receive back is the resonance frequency with a varying amplitude.

that reduces the optimisation to easy testing like "from how far you still detect an echo".

If anybody else has better info, I'd love to hear it !


ps I do have an oscilloscope, and indeed that comes in handy.
the arduino itself is usable as a frequency generator. maybe even as a replacement scope. using the adc is a challenge, but there is another way :
detect whether the signal is above a threshold voltage using the comparator, and compile a few runs at varying threshold values.
Sampling this way can be done at about 2 Mhz in a 16 Mhz Arduino.
you have about 512bytes = 512 samples x 8 runs. Aiming at about 10 samples per wave the max frequency would be 200 khz.
This assumes that the arduino knows when to start measuring, but that is easy when it is generating the chirp itself...

[Reply #18 on:]

I wonder if I'll get a cheap sensor in my city :/

[Reply #19 on:]

Well, you can do it a lot cheaper if you are willing to design and build your own sensors.

I just picked up a few ultrasonic transducers from (http://www.goldmine-elec-products.com/prodinfo.asp?number=G951) and am in the process of building my own range finder.

Anyway, they are on sell right now for 49c a piece. Can't beat that

[Reply #20 on:]

Seriously? That's awesome!
But by the time you post it to me, it'll be more than $15 again
but thanks for the link!

[Reply #21 on:]

The deal lasts till the 5th.... you still get some time.

[Reply #22 on:]

Oops... spoke too soon. Just checked the website again, it seems that the deal ended yesterday...

[Reply #23 on:]

Holy crap
Thanks though