176 lines
8.3 KiB
Plaintext
176 lines
8.3 KiB
Plaintext
The red box generates three sets of tones to simulate currency. ALL redbox
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tones are a combination (DTMF) of 1700 + 2200. A nickel is a 60 ms tone. A
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dime is 2 60 ms tones, separated by a 60 ms pause. Finally, the quarter is a
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COMBINATION of 5 35 ms tones, each one separated by a 35 ms pause.
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Each time the pushbutton is pressed, it triggers half of IC1,
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configured as a monostable multivibrator to energize the rest of the circuit
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for a length of time determined by the setting of the coin selector switch.
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This in turn starts the other half of IC1, configured as an astable
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multivibrator, pulsing on and off at regular intervals at a rate determined
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by the 50k pot between pins 12 and 13. The output of the astable thus
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alternately powers of IC2, configured as a square wave oscillator, providing
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the required 1700hz and 2200hz to the op amp which acts as a buffer to drive
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the speaker.
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For alignment, a frequency counter and triggered sweep oscilloscope are
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extremely handy (but not absolutely necessary.)
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Install a temporary jumper from +9v supply to pin 14 of IC2 and
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temporarily disconnect the 0.01uF capacitors from pins 5 and 9 of IC2. Power
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up the circuit. Measuring the output from pin 5 of IC2 with the frequency
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counter, adjust the 20k pot between pins 1 and 6 for an output of 1700hz.
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Now adjust the 20k pot between pins 8 and 13 for an output of 2200hz from pin
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9 of IC2. Remove the temporary jumper and re-attach the capacitors to pins 5
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and 9. (Note: if no frequency counter is available, the outputs can be
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adjusted by ear one at a time by zero-beating the output tone with a computer
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generated tone of known precision.)
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Next, temporarily disconnect the wire between pins 5 and 10 of IC1. Set
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coin selector switch in the "N" (nickel) position. With the oscilloscope
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measuring the output from pin 9 of IC1, adjust the 50k pot between pins 12
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and 13 of IC1 for output pulses of 60 millisecond duration. Reconnect the
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wire between pins 5 and 10. (Note: If no scope is available, adjust the
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pulse rate by ear using computer generated tones for comparison.)
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The remaining adjustments are made by ear.
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Leave the selector switch in the "N" position. Adjust the 50k pot
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labelled "Dime" for a quick double beep each time the pushbutton is pressed.
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Finally, set the selector to "Quarter". Adjust the 50k pot labelled
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"Quarter" until exactly 5 very quick beeps are heard for each button press.
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Don't worry if the quarter beeps sound shorter and faster than the nickel and
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dime ones. They should be.
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If all went well to this point, your red box should be completely aligned
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and functional. A final test should now be conducted from a payphone using
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the DATL (dial access test line) coin test. Dial 09591230 and follow the
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computer instructions using the red box at the proper prompts. The computer
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should correctly identify all coins "simulated" and flag any anomalies. With
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a little discretion, your red box should bring you many years of use.
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Remember, there's no such thing as spare change.!
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Parts list for Red Box
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Semiconductors
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--------------
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(2)556 dual timer
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(1)741 Op Amp
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(1)1N914 Switching Diode
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Resistors
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---------
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(6)10k (1)4.7k
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(2)100k
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(4)50k PC Mount Potentiometer
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(2)20k Multi-Turn Potentiometer
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Capacitors
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----------
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(10)0.01uF (1)1.0uF
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(2)10.0uF Electrolytic
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Miscellaneous
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-------------
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(2)14 Pin Dip Socket
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(1)8 Pin Dip Socket
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(1)3-position Rotary Switch
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(1)Momentary Push-Button Switch(normally open)
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(1)SPST Toggle Switch
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(1)Speaker or Telephone Earpiece Circuit Board
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(1) Box
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(1) 9v Battery Clip
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Mounting Hardware
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/
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Schematic part variables list.
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Resistors
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---------
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R1 - 10k R2 - 10k R3 -4.7k R4 - 10k R5 - 10k R6 - 50k
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R7 - 50k R8 - 50k R9 - 50k R10- 20k R11- 10k R12- 10k
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R13- 20k R14-100k R15-100k
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Capacitors
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----------
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C1 - 0.01uf C2 - 1N914 switching Diode C3 - 1.0uf C4 - 0.01uf
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C5 - 0.01uf C6 - 10uf C7 - 0.01uf C8 - 0.01uf C9 - 0.01uf
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C10 - 0.01uf C11 - 0.01uf C12 - 0.01uf C13 - 0.01uf C14 - 10uf
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Switches
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--------
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S1 - SPST toggle
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S2 - Momentary push button N.O. labeled "Deposit"
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S3 - 3-position rotary switch
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Miscellaneous
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-------------
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g - Ground
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@q - Label "quarter"
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@d - Label "dime"
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@n - Label "NICKEL"
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