[Lab] leads on an ultrasonic range finder

Ken McKinnon klmckinnon at rogers.com
Tue Feb 11 17:28:51 EST 2014

Sounds like a pretty elegant solution.


On 2014-02-11 1:24 PM, Adam Hill wrote:
> 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 
> <mailto: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 <http://rubber-power.com/>
>>     Contact: darcy at inventorArtist.com
>>     <mailto:darcy at inventorArtist.com> | 613-563-3634
>>     <tel:613-563-3634> by appointment (no text)
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