Polaroid Sonar One Step Camera

© Brooke Clarke 207


Sonar One Step camera

Background

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.

Idea

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 circuitry.
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.

Opening

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 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.

  • Polaroid Sonar Ultrasonic Transducer mounting clip
    Polaroid Sonar One Stip Ultrasonic Range Finder PCB

    Polaroid Sonar One Step Ultrasonic Range Finder & Transducer rermoved

    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

    Pin #
    Wire
    Function
    1
    X-
    sensor ground
    2
    X+
    sensor hot
    3
    VIO
    Flash & Exposure Counter
    4
    B/W
    Exposure Counter
    5
    BLU
    Aux Pluse Gen (Focus move)
    6
    GRN
    Aux Pulse Gen (Focus move)
    7
    R/W
    Shutter Flex Ckt
    8
    Lite Blu
    Shutter Flex Ckt
    9
    Yel
    Aux Pulse Gen (focus move)
    10
    Bk/W
    Ground (batt -)
    11
    Orn
    Aux Pulse Gen (focus move)
    12
    Wht
    Focus Ratchet Coil
    13
    Wht
    Focus Ratchet Coil
    14
    Gry
    Flash & Shutter Sw
    15
    Red
    Focus Motor
    16
    Blk
    Focus Motor
    pin 13 part of pin 14, i.e. permanent jumper

    uxiliary Pulse Generator (focus move)  =  Patent 4199246 Fig 1 #26
    Focus Motor  = Patent 4199246 Fig 1 #24

    Focus Assembly

    Polaroid Sonar One Step Focus Assembly
    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.


    Main Assembly

    Film Advance & Exposure Counter

    Polaroid Main Assy openedThe film 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 counter.

    Shutter Control

    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.

    Optics PCB

    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 & shutter switch
    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

    Shutter Switches

    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 Socket. 
    A short red wire is soldered to the Shutter Control flex circuit.
    The Lite Blue (8) wire goes to the Auto Focus PCB.

    Flash Socket

    Four terminals:
    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.

    Power Source

    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 (typically 350 volts) or build a custom blocking oscillator.

    Polaroid Patents

    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 often undetected.
    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 Polaroid camera
    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
    3641889
    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 Self-Monitoring Features
    *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
    3882522 Non-Cocking Springlesss Shutted Developing Two Parameter Exposure Regulation
    3979762 Modular photographic system, 396/541 ; 396/30 - One Step w/o Auto Focus
    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, 1977
    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 transducers
    3814864 Condensor Microphone having a Plurality of Discrete Vibratory Surfaces, 381/174, June 4, 1974 to Victoreen
    not ultrasonic, just normal audio
    3041418 Transducers,RCA, 381/174 ; 381/163; 381/426 - improved condenser mike
    4152825- battery
    *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 schematic
    4199237 Low scene brightness indicator for use in a photographic camera, Savage (Polaroid), Apr 22, 1980, 396/165 ; 396/201; 396/296
    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 efficiency.

    Links

    SONAR as I Have Done it - how to open camera and remove good stuff
    SensComp - the Polaroid Electrostatic transducers & also piezo film transducers - old range finder data sheet w/schematic -
    TI special ICs: TL851 & TL852 

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    created 3 June 2007