Ramsey Electronics CW-700, Manual

Page: 13 / 27

CW700
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13
ˆ 13. Now that we have installed most of the touch sensitive circuit, we
will install the digital chip that will detect your touch. Identify U1, a 14 pin
chip labeled 74HC04. On the chip, there is a little notch, dot or band on
one end. This is there to help you put the chip in correctly. When
properly inserted, the marking should face towards the back of the
board. You may also note that the outline of the chip with the notch in
the proper direction is also printed on the board. Solder the chip
carefully to the board making sure to get good connections.
ˆ 14. Identify D1, a 1N4148 glass bead diode. Looking at the diode, you
will notice that there is a black band printed on one end of it. When
bending the diode leads, it is best to bend them at first with a pair or
needle nose pliers. The leads may break off if there is too much strain
on them. After you initially bend them, you may use your finger or pliers
to bend them the rest of the way.
Diodes act like a one way valve; they let the electrons go in one direction,
but not in the other. For this reason, it is very important to install the diode
pointing in the right direction, or polarity. As a rule of thumb for this kit,
please insert all parts according to their outline on the board. For diodes, the
direction of the bands must match.
ˆ 15. Insert D2, 1N4148 glass bead diode, paying attention to the polarity.
ˆ 16. Install R5, 1K ohm resistor [brown-black-red].
ˆ
17. Install R3, 1K ohm resistor [brown-black-red].
ˆ 18. Install R2, a 10K ohm resistor [brown-black-orange]. Mount it
standing up.
ˆ 19. Install R1, a 10K ohm resistor [brown-black-orange]. Mount it
standing up also. (All this standing up must make the resistors tired!)
ˆ 20. Install C3, a .01uF disc capacitor [marked .01 or 103 or 10nF].
ˆ 21. Install C2, .01uF disc capacitor [marked .01 or 103 or 10nF].
Congratulations! With the exception of the sensitivity control and the
paddles themselves, you have built the touch sensitive portion of the circuit.
Take a well deserved break. We encourage you to check over your work
now, and try to identify and correct any mistakes that you may have made.
You will also want to clip any extra leads if you haven’t already done so.
Please save the leads. You will need some later! The next part of the circuit
that you will build is the switch circuit. You are going to construct this portion
of the circuit next, because it will provide you with more soldering practice
before you install the computer chip.