Ultrasonic distance measurement master <-> node

A project log for autoCut

robot lawn mower on steroids

schuhumischuhumi 09/27/2014 at 18:065 Comments

Meanwhile I got a working master and node. The master can send a package (one byte so far) to the node, the node responds and the master calculates the distance:

Keeping in mind that it is  calibrated rather loosely the results are very good. The distance value is very stable and +-0.5cm accuracy should be archieveable.

What the data package looks like:

I need to increase the number of parity bits, because two bits result in an easy 25% chance for the parity to be right anyways.


thorn wrote 06/18/2016 at 17:21 point

Can You please add the schematics ( the one You used in the videos) in github. The circuit I used doesn't reach more then 4 meters :(.
Beste Grüße aus Bremen, Tom

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Electronic Man wrote 10/09/2014 at 14:02 point
What distance do you think it can work in?
How about wind?
How about obstacles / multipath signal (same issues as GPS?)

Look very nice

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schuhumi wrote 10/09/2014 at 19:46 point
Thank you :)

-> Distance: I'm not sure... There's plenty of room for improvements, these
problems are related to that:
___-> Using a max232 to amplify the signal to transmit works crap.. I might need
separate voltage booster and H-bridge
___-> The transmitter and receiver capsules are very limited in the angle they
transmit/listen. They don't behave like usual speakers/microphones at all, but
this is what I need
___-> As stated in the video a dynamic signal boost for the receiver is needed.
I haven't implemented this yet [busy with improvements on mowing system, update
very soon], so unclear how well this will work
___-> Noise will definitely increase along with amplification. Therefore some
additional bandpass filter might be necessary

-> Wind: I haven't had any problems with this so far, and with sound traveling
at 343m/s it shouldn't be too much of a problem I guess.

-> Obstacles: Since "receiver capsules are very limited in the angle they
transmit/listen" obstacles can be a problem. Of course multiple nodes would
overcome this issue, but with better/wide angle receivers and transmitters it
should be pretty much the same as we experience in our hearing range

-> multipath signal: This is where I like the system the way it works: The
receiver capsules have a small weight oscillating at 40KHz when receiving a
40KHz wave. The system uses this effect: oscillating means 0-bit, phase shifting
by 180° so that the weight must stop it's oscillation and build up again with
the shifted phase means 1-bit. Now when a reflected wave arrives at the receiver
it is not strong enough to disturb the ongoing oscillation (in most cases) -
awesome isn't it :D

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Mark Grint wrote 10/01/2014 at 15:28 point
Hi Simon, you've nailed an important piece of the puzzle here. Are you interested in commercialising this functionality? Mark

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schuhumi wrote 10/09/2014 at 19:14 point
I actually thought about that. I mean there's no easy to use system for small range positioning - especially indoors. Crowdfunding might be an option as soon as I got it working stable and realiable. We will see.. It mainly depends on how much spare time I have at the point I get it working and whether I'm able to fulfill the strict requirements in EU/Germany.

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