262 lines
10 KiB
Plaintext
262 lines
10 KiB
Plaintext
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How to build a BLUE BOX
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-----------------------
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We all know that the touch tone frequencies are composed of 2 tones (2
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different frequencies) so that is the reason why we have 2 VCO's (Voltage
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Controlled Oscilators). We will call then VCO#1 and VCO#2. If you have
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noticed VCO#1 and VCO#2 are exactly the same type of circuits. That is why
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only 1 was drawn. But remember that whatever goes for VCO#1 also goes for
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VCO#2. Both VCO'S are composed of a handfull of part. One chip, two
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capacitors, 2 resistors and five potentiometers. All of this will give you
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(when properly calibrated) one of the freqencies necessary (the other one
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will come from VCO#2) for the operation of the Blue Box. Both of these freqs.
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will be mixed in the speaker to form the required tone.
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This is one of the most sophisticated designs I have ever made. Why?
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Because other designs will drain the battery after 10 calls. This design will
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make them last 10 months!!!!! But never the less, don't forget to put in a
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switch for on and off. Ok let's build the two VCO'S and calibrate the unit
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before we get to the keyboard construction.
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VCO CONSTRUCTION:
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----------------
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TOOLS REQUIRED
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1 ocilliscope(optional but not req)
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1 Freq. counter (REQUIRED)
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1 Volt meter " " "
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Electronics tools (Pliers,drll,
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screwdrivers, etc.)
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=====================================
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PARTS
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R1 1.5K RESISTOR 5%
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R2 1K RESISTOR 5%
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C1 .1uf ELECTROLYTIC CAPACITOR 16VDC
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C2 .01uf " " (MYLQR)16VDC
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IC1 2207 VCO CHIP BY EXAR ELECTRONICS
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Remember the above only says
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VCO#1 but the same is for VCO#2
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R3-R4 150 OHM RESISTORS 5%
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C3-C4 .1 uf ELECTROLITIC CAPACITOR
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10VDC
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P1-P10 200K TRIMMER POT - 20 TURNS
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DIODES USED IN THE KEYBOARD
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ARE 1N914 TYPE (40 OF THEM) &
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13 SWITCHES FOR THE KEYBOARD
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SPST MOMENTARY.
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SPKR=YOU CAN USE A TELEPHONE SPEAKER
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FOR THIS (IT WORKS BEST) BUT
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REMEMBER TO TAKE OUT THE DIODE
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THAT IS CONNECTED ACCROSS IT.
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=======================================
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IMPORTANT NOTES
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1. DO NOT USE ANYTHING ELSE OTHER
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THAN A MYLAR CAPACITOR FOR C2.
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2. PINS 10,9,8 SHOULD BE TIED
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TOGETHER AND BE LEFT FLOATING.
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3. ALL RESISTORS SHOULD BE 5%!
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NOTHING ELSE!
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4. A TELEPHONE SPEAKER GIVES THE
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BEST RESULTS.
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=======================================
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TROUBLE SHOOTING
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By now you should have constructed the two VCO'S on a bread board or
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anything that pleases you. Check for cold solder joints, broken wires,
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polarity of the battery, etc. Before we apply power to the VCO'S we have to
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adjust the pots for their half way travel point. This is done by turning them
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21 turns to the right and then 10 turns to the left. Do the same for all ten
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of them.
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Now apply power to the unit check to see that you have power in the chips
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by putting the positive lead of your volt meter on pin 7 and the negative
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lead on pin 12. If you do not have anything there turn off the unit and
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RECHECK THE WIRING.
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When you get the right voltages on the chips, connect a diode to a piece
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of wire (look at fig. 2 for the orientation of the diode) from ground to any
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pot at point T (look carefully at the schematic for point T it is labeled
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T1-T10 for all pots). You should be able to hear a tone, if not disconnect
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the lead and place the speaker close to your ear and if you hear a chirp-like
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sound, this means that the two VCO'S are working if you don't, it means that
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either one or both of the VCO'S are dead. So in this case it is always good
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to have an ocilloscope on hand. Disconnect the speaker from the circuit and
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hook the ocilliscope to 1 of the leads of the speaker & the ground from the
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scope to the ground of the battery. Connect again the ground lead with the
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diode connected to it from ground to any pot on the VCO that you are checking
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and you should see a triangle wave if not turn the pot in which you are
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applying the ground to until you see it. When you do see it do the the same
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for the other VCO to make sure it is working. (amplitude is about 2VAC). When
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you get the two VCO's working you are set for the adjustment of the
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individuals pots.
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Adjustment
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----------
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Disconnect the speaker from the circuit and connect a freq. counter (the
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positive lead of the counter to one of the speakers leads that belongs to
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VCO#1 or connect it to pin 14).
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Connect the negative lead to the battery negative and connect the jumper
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lead with the diode from ground to pot number 1.T1. ( the first pot number
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1 point T1) if you got it working you should hear a tone and get a reading
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on the counter. Adjust the pot for a freq. of 1700HZ and continue doing the
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same for pots 2-5 except that they get differents freqs. which are:
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$$$$$$$$$$$$$$
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$ P1= 1700hz $
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$ P2= 1300hz $
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$ P3= 1100hz $
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$ P4= 900hz $
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$ P5= 1500hz $
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$$$$$$$$$$$$$$
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Now disconnect the freq. counter from the speaker lead of VCO#1 or from
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pin 14 (which ever you had it attached to at the beginning) and connect it
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to the speaker lead of VCO#2 or to pin 14 of VCO#2 and make the same
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adjustments to P6-10.
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$$$$$$$$$$$$$$$
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$ P6= 1100hz $
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$ P7= 700hz $
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$ P8= 900hz $
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$ P9= 2600hz $
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$ P10= 1500hz $
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$$$$$$$$$$$$$$$
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When you finish doing all of the pots go back and re-check them.
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Keyboard
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--------
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If you look at FIG-2 you will see that the keys are simple switches.
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Connected to a ground and two diodes on the other end. these diodes are used
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to simplify the construction of the keyboard because otherwise the
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distribution of the ground signal for both VCO'S would have been done
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mechanically. The diode will go to VCO#1 and the other will go to VCO#2.
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FIG-3 shows the arrangement of the keys on the keyboard.
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Below is a table that will help you connect the keys to the required VCO's
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pots.
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(-FIG 2-)
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-----!-----!--------!--------!-------
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! ! ! !
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TO ! TO ! FREQ ! FREQ ! KEY
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POT ! POT ! OUT: ! OUT: !
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ON ! ON ! ! !
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VCO1! VCO2! ! !
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-----!-----!--------!-------%!-------
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1 ! 06 ! 1700hz ! 1100hz ! C
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2 ! 10 ! 1300hz ! 1500hz ! 0
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1 ! 10 ! 1700hz ! 1100hz ! E
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4 ! 07 ! 0900hz ! 0700hz ! 1
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3 ! 07 ! 1100hz ! 0700hz ! 2
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3 ! 08 ! 1100hz ! 0900hz ! 3
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2 ! 07 ! 1300hz ! 0700hz ! 4
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2 ! 08 ! 1300hz ! 0900hz ! 5
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2 ! 06 ! 1300hz ! 1100hz ! 6
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5 ! 07 ! 1500hz ! 0700hz ! 7
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5 ! 08 ! 1500hz ! 0900hz ! 8
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5 ! 06 ! 1500hz ! 1100hz ! 9
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- ! 09 ! ------ ! 2600hz ! X
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Remember that in FIG-2 it's the same for each key except the "X" key,
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which only takes one diode.
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few KEYS to the diagram:
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Cx is capacitor #x Denoted by: ---| |
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---
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Px is Pot or Variable resistor #x Deno
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ted by :/
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\
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/<--
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\
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Rx is resistor #x Denoted by /\/\/\/\
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SCHEMATICS
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The XR-2207 chip is a Voltage-Controlled Oscillator and a 14 pin device
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thus you must be very careful when soldering the parts to this device. It is
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a little dificult to actually draw a schematic on an 80 character screen
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using limited graphics, but I will give
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it a try.
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TO GND_____________
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___
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C2 C3 ___
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_||_ |
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| | _____|__9v+
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` ` ` ` ` ` ` |
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------------------------------- |
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7 6 5 4 3 2 1 | |
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| < |
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|8 9 10 11 12 13 14| |
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------------------------------- |
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` ` ` ` ` ` ` |
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--| |--------| | |
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|C1 R2 | R1 |
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GND ______|___/\/\/\/\______|_____/\/\/\/\______|
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is is a diagram of how to locate the different pins on the chip.
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Please notice that pin one (1) is the closest to the notch on top of the
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chip. The first thing we'll do is to connect power to the chip (remember that
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you need to build two (2) of these to get a complete system) this is
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accomplished by connecting the positive wire of the battery lead to pin#1 one
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leg of R1 and R2 is soldered to pin#11. The other leg of R1 goes to pin 1
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or to the d. C1 goes between pin 10 and ground. The timing capacitor or C2
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goes between pins 2 and 3 of the chip. Pins 8 and 9 should be grounded to
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ground. Pin 14 is the output and this is where one leg of C4 (C3 goes on the
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other VCO) in series with R3 (the same goes for the other VCO) and to one
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lead of the speaker.
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The trimmer pots P1 to P10 should be grouped in groups of 5 pots each.
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The way you group it is by soldering one end of the pot to each other leaving
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the wiper and the other end free.
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| This end goes to pin 6 of the chip
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_____________|_____________
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/ / / / /
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\ \ \ \ \
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/<- /<- /<- /<- /<-
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\ | \ | \ | \ | \ |
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/ | / | / | / | / |
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P1 P2 P3 P4 P5
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And finally this is the way each key should be wired.
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diode
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he contact of the
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|--------- \------ key
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to Px ------>|-----| |
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diode |
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-----
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--- Ground
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