Polaroid Sonar One Step Camera

Background

Idea

Opening

Use the slide switch just below the shutter release to open the film door.

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 removed.

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 any wires.

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.

The 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.

Ultrasonic Transducer

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 transducers offered by the Polaroid spin off SensComp.
The 600 Instrument Transducer 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 pf capacitor.

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.
Stamped 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 vias.
At the left edge "Made In Taiwan".  A (TI) logo in the lower right corner.
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 electrolytic.
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 Q filter.
Right next to T1 is a green cap marked .0022k630 which connects the tranducer hot lead to T1 input.

Range Finder PCB Pin Table

Focus Assembly

Main Assembly

Polaroid Patents

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