The ultrasonic transducer used in the
Polaroid Sonar cameras like the One Step and SX-70 should make an
excellent wide band ultrasonic moicrophone, like you would want to use
for listening to bats
These have a diaphragm that much larger
than the under one inch
diameter electret condenser mikes and is much more sensitive.
They also were designed for ultrasonic use with pulse signals and so
inherently have wide bandwidth.
Next is to figure out how to take it apart and recover not only the
1.5" diameter ultrasonic transducer but also the associated 200 VDC
power supply and amplifier if any. Got this one on eBay for under
$5. There were a number of "Sonar" type Polaroid cameras made,
the SX-70 and the "Land" series, but not all of them have the
ultrasonic transducer. But you can't miss it if you see a photo
of the camera
There's a Polaroid spin off company
that still makes these transducers
but they don't seem to serious about selling them. You can get a
kit with some transducers and circuitry for a range finder application
or a minimum order quantity of them, but no single sales and no
distributors. They do have two versions, one of which is made
from materials that can survive outdoors, so would be a good choice for
a permanent installation.
There are a couple of ways this can be
used relative to a microphone.
1) Just use the ultrasonic transducer from the camera and use all new
2) In addition to the transducer also use the 150 VDC power supply, the
pre amplifier, the final amplifier, but disable the variable Q filter
and instead of the ramping gain control bring out a manual gain control.
There are web sites made by robot
builders that have details on getting the ultrasonic range finder and
transducer out of the camera.
Use the slide switch just below the shutter release to open the
The film door is held on at the hinges which are formed from
metal parts and the hinge is a weak rivet. You can pry between
the two metal parts and they will seperate popping the rivet. Do
this and remove the film door.
Pry between the front panel that surrounds the lens, viewfinder,
transducer, etc. and the rear body and it will come loose and can be
At the left and right lower part of the film compartment you can
gently pry the guts forward out of the body. Be careful to free
There is a metal clip a little longer than the transducer holding
it to the frame just squeeze the two ends of the clip toghther and
slide it out freeing the transducer.
wires connecting to the PCB have sockets crimped onto them, just pull
the wire and socket from the PCB. Leave the Transducer connected to the
PCB. A single plastic finger holds the board at the top center,
just flex it up and hinge the PCB down and remove the PCB.
The max dimensions are 1.7" dia x 0.38 thick. The diaphragm is
about 1.5" in diameter.
This is about the same as the 600 series of electrostatic
offered by the Polaroid spin off SensComp.
is typical and covers 20 kHz to 100 kHz with about +/- 5 dB
variation. It requires 200 Volts bias and looks like about a 450
12 June 2007 - I had hoped that the Range Finder PCB contained a 200
VDC power supply for the bias voltage. But now think the bias
gets generated by rectifying the transmitted pulse and charging a
capacitor, which then will supply the DC bias needed to receive the
echo. But I don't like the idea of sending a pulse when trying to
listen to bats.
Note that the diaphragm is much larger than a wavelength at 50 kHz
(about 1/4"). This implies that the off axis side lobes will be
closer together and the nulls deeper than you would get using a smaller
diameter microphone. For example professionals use 1/4" condenser
microphones which have very well behaved frequency and spatial response
at 50 kHz, but are much more expensive and less sensitive.
Range Finder PCB
This transducer is attached to the PCB at pins 1 (ground at the top of
the board) and pin 2 hot.
The bottom of the board is marked 735710 in trace metal with solder.
in yellow ink along the wire connectors is 7840 and a symbol - maybe a
week 40 of 1978 date code and QA stamp. It's double sided with
At the left edge "Made In Taiwan". A (TI) logo in the lower right
C6, C10, R2 are marked on the PCB but not installed. An R2 pad is being
used to jump to another nearby pad.
3 each 16 pin DIP packaged ICs (5-89 transmitter, HV gen?, 0A810=TL852
receiver, 7-88=TL851 control) and an 8 pin DIP (SN28728P).
2 Inductors or Transformers both with adjustable slugs and 4 pins.
R6 is a 20 k pot.
A small blue cylindrical part that looks like a 1/8 watt resistor is
connected right next to IC5-89 pins 16 and 13, is a diode
C8 has been replaced by a resistor, C7 by a SMT cap inside a glass case
(looks like a diode), and C3 is now a tantalum instead of an
The green plastic wire guide next to the 16 pins on the PCB has the
wire color for each pin.
The yellow palstic rectangle above IC1 and IC2 is a 420 kHz reasonator
for the TL851 timing clock.
The shiny metal can in the upper left is T1, part of the transducer
input. The round ferrite is L1 a 1 mH coil that's part of the variable
Right next to T1 is a green cap marked .0022k630 which connects the
tranducer hot lead to T1 input.
Range Finder PCB Pin Table
Gen (Focus move)
Gen (Focus move)
Gen (focus move)
Gen (focus move)
pin 13 part of pin 14, i.e. permanent
uxiliary Pulse Generator (focus move) = Patent 4199246 Fig
Focus Motor = Patent 4199246 Fig 1 #24
Contains the focus DC motor (twisted red/black leads) the red focus
ring with 40 holes. On either side there is an LED and photo
transistor (siamese blur/green and siamese yellow/orange).
There are also a siamese pair of white wires that go to a small
solenoid that activates a ratchet function on the focus ring.
Don't know what that's for.
Film Advance & Exposure Counter
advance motor is controled from the paper flex circuit although it
has a direct ground connection to the battery terminal (black/yel
bands). There are 4 leave switches that are the digital exposure
The exposure knob has a hollow shaft that allows light to fall on a
photo sensor connected to the paper flex circuit. When the
exposure knob is turned it rotates a filter that has different segments
that are graduated in transmission thus allowing in different amounts
of light. The filter is made from a single piece of light gray
plastic. The hole lets the most light by, then a thin sector, a
thicker sector and third thicker sector then the full thickness.
There's a coil to trip the shutter.
The flex circuit has two 14 pin DIPs and one 16 pin DIP, a diode and a
resistor and the exposure control 2 pin clear TO-92photo sensor. The
shutter is composed of three thin metal plates that slide on plastic
location pins. There's a shutter position where instead of being
completly closed a small hole is left open at the center, maybe
something to do with very bright light like a small f stop.
Next to the expsoure knob, but on the side opposite to the lens, is
what I'm calling the optics PCB.
has pair of yellow wires to one pin terminal - Flash connector &
Red & Black wires to red LED
Green/Wht wire to pin terminal - to Shutter assy
Black wire to pin terminal - battery - & BattGnd
hole cut in PCB to allow it to look forward with photo cell
This assembly has two normally closed switches that look like they are
operated by the focus ring.
One of these has a gray (14) wire.
The yellow wire goes to the Optics PCB and continues to the Flash
A short red wire is soldered to the Shutter Control flex circuit.
The Lite Blue (8) wire goes to the Auto Focus PCB.
Yellow - Optics PCB - Shutter Switch assy
Violet - pin 3 of Auto Focus - Exposure Counter switch
Gray - pin 14 Auto Focus - Shutter Switch assy
Red - positive battery terminal - Exposure Counter switch
There is a longer slot in the flash socket part that sits over a row of
8 contacts that are part of the Shutter Control flex circuit.
It's not to practical to use the power
supply since it's very mixed up with the rest of the camera.
Alternate and untested ideas are to use the power from a single use flash camera
volts) or build a custom blocking oscillator
Patents are a very good way to get an
idea of how something works. Not as good as a service or
maintence manual, but much better than nothing.
* patents look good for this effort.
152858 ? typo
3454922 - ultrasonic pulse distance measuring device. separated
fixed frequency bursts are transmitted by a transducer, and a reflected
echo is received by the same transducer after a period of time related
to target range. When a fixed frequency ultrasonic sound is
utilized, it has been found that subjects within the acceptance angle
of the transducer, and within the field of view of the camera, are
3475651 Charging and Triggering Circuits for Pulse Electrical Devices
Such As Flash Lamps, Oct. 38, 1969
3522764 Rangefinding and Focusing System for Photographic Cameras and
the like, 396/103 ; 367/96; 396/105; 455/344; 455/91; D16/211- an add
on dual transducer auto focus system for the older bellows type
3563805 Thin, Flat Primary Cells and Batteries, Feb. 16, 1971
3608454 Imbibition Interval Timer and Annunciator 52/35 ; 52/285.3;
52/34 - i.e. wait for film to develop timer
3617387 Battery Construction Having Cell Components Completely
Internally Bonded With Adhesive, Nov. 2, 1971
3734780 Flat Cell Battery With Both Terminals on One Face, May 22, 1973
3770504 High Discharge Rate Multicell Battery, Nov. 6, 1973
3774516 Photographic Control System and Apparatus having
*3791278 Photographic Apparatus with Solenoid Powered
Instrumentalities, Feb. 12, 1974
3820128 Flash Photographic Control System, June 25, 1974
3858227 Adapter Apparatus for Flash Firing System
Non-Cocking Springlesss Shutted Developing Two Parameter Exposure
3979762 Modular photographic system, 396/541 ; 396/30 - One Step w/o
4005449 Flash photographic system with camera inhibit feature
4052728 Modular photographic system assembly, 396/33 ; 396/541 - One
Step w/o Auto Focus
4064519 Regulated Strobe for Camera with Sixth Flash Inhibit, Dec. 20,
4074295 Compact Accessory Strobe for Cameras with Battery Enclosed Film
Pack, Feb. 14, 1978
*4085297 Spring force biasing means for electroacoustical transducer
components, 381/191 ; 381/173
capacitance type electroacoustical
3814864 Condensor Microphone having a
Plurality of Discrete Vibratory Surfaces, 381/174, June 4, 1974 to
not ultrasonic, just normal audio
3041418 Transducers,RCA, 381/174 ;
381/163; 381/426 - improved condenser mike
*4156567 Ranging and lens focusing module for foldable cameras,
May 29, 1979, 396/89 ; 396/348 - probably the foldable SX-70
*4168895 Camera having auto focus module, Sep 25, 1979, 396/105 -
probably Sonar One Step camera (non folding)
4182561 Fast charging electronic flash device01/08/1980 - may have
4199237 Low scene brightness indicator for use in a photographic
camera, Savage (Polaroid), Apr 22, 1980, 396/165
This is very similar to the flip dot
sign pixels, but is only a single bit.
*4199246 Ultrasonic ranging system for a camera, 396/101 ; 352/140;
367/101; 367/96; 396/105 - The preferred form of the
frequency-modulated burst is a leading half in the form of a chirp
(using radar terminology) wherein the frequency decreases with time,
and a trailing half in the form of a constant frequency equal to the
lowest frequency of the chirp.
4265530 Shutter Blade Drive System - feels like the Sonar One Step
*4331409 Photographic apparatus with dual function
sonic transducer, 396/105 ; 396/283 - block
diagram outline of ranging PCB and some curcuit details 50-65
khz is used for ranging and 3-5 khz as a speaker although at much lower