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by
Dennis Clark
It will be July when you read this, but it is the snowy
month of May for me as I write this. So, let’s heat things
up and get right to the questions.
Q. I have scavenged a Polaroid Spectra sonar transducer and board. I have read your page at www.seattlerobotics.org/Encoder/200010/dlcs
onar.html. I’m not sure about the purpose of the small
board that is above the ranging PCB assembly. What is the
function, how does it interact with the sonar unit, and
what are the parts? Have you worked with an Arduino
board with this application?
my new circuit for using this version of a Polaroid SONAR.
How This Board Works
— Richard
A. Ah, the hacked Polaroid camera SONAR! It doesn’t seem as popular as it was 10+ years ago before all of the affordable small SONARs appeared on the
market, but we shouldn’t ignore it! These SONAR units are
not too difficult to get to work and they have a greater
range than the commonly used SONARs
today. When I wrote that article, it
actually came from a web page of mine.
I gave example circuits and code for the
Parallax BASIC Stamp II and the Motorola
68HC11 — two of the more popular
robot controllers of the day. Your question
allows me to revisit those glorious
hacking days and use the much faster
and more convenient Arduino platform.
Before your question, I had not tried this
on the Arduino. Thanks for getting me to
amend that omission! Yes, it does work,
but not with the circuit that I showed in
my article. The Stamp used a PIC which
worked fine with the sub-3V output of
that board, the Arduino’s AVR processor
apparently does NOT like the voltage level
of this circuit. I modified the design a
little and it works great. Figure 1 shows
This circuit is designed to do two things. The first is to
programmatically power the SONAR board on and off. The
Arduino Digital 2 ping does this via Q1. When D2 is high,
the PNP transistor (and SONAR board) is off. When D2 goes
low, then Q1 turns on and the SONAR board is ready to
work. C2 is a reservoir capacitor that stores energy for the
high current needs of the SONAR when you ping it.
Figure 1. SONAR control board schematic.
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