[Lab] leads on an ultrasonic range finder

[Adam Hill]

I can confirm Ken's suspicions, at least anecdotally. I was not able to do
a lot of debugging at the time, but when I tried using long leads with a
similar sensor it was completely unreliable. Instead of fighting with
physics, my solution was to go wireless. I created an adhoc network with an
airport express and connected a beagle bone to the network which was close
to the proximity sensor. That gave me the effective range of the wifi
network while keeping the sensor components close to the data collection
hardware.

Best of luck,
-ah


On Mon, Feb 10, 2014 at 7:44 PM, Ken McKinnon <klmckinnon at rogers.com> wrote:

>  If your talking a SRF04 or similar, there are a couple of issues you need
> to consider.  These are driven at 5VDC, and use a chunk of current while
> transmitting the sensor pulse chain.  On a long lead, you may have voltage
> droop on the 5V line at the sensor end.  The result may be that the sensor
> resets, doesn'r respond correctly or somewhere in between (read errattic
> behaviour - the worst).  This likely may be mitigated with a decent sized
> cap between VCC and ground at the transducer/sensor.
> The trigger is a 10 usec pulse.  On a long lead, this can become rounded
> due to the capacitance of the cable, so a start pulse may not be seen.  The
> same goes with the recieve pulse, although since it is longer, it is
> unlikely to cause any problems.
> If I were to try this, I would use a reasonably heavy guage cable, say 24
> AWG or better, shielding will help, but twisted won't as the signals are
> single ended.  If it doesn't work, tack solder a 47 uf cap between
> VCC/Ground and try it.   If that doesn't work, it gets a bit more
> complicated....
>
> Ken
>
>
> On 2014-02-10 4:58 PM, Darcy Whyte wrote:
>
> Can anybody think of a reason I shouldn't have 10' wires on an ultrasonic
> range finder?
>
>
>
>
>  --
> Darcy Whyte
>
>  Art+ inventorArtist.com <http://inventorartist.com/> | Aviation
> rubber-power.com
> Contact: darcy at inventorArtist.com | 613-563-3634 by appointment (no text)
>
>
>
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