[Lab] leads on an ultrasonic range finder

Ken McKinnon klmckinnon at rogers.com
Mon Feb 10 19:44:37 EST 2014

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 


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 by appointment (no text)
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