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different components.
29. Install "lay-down" 1K ohm resistors R2, R1, R3, and R4 (brown-black-
red) .
30. Install "stand-up" resistors R14, R15, R16, R17, all 100 ohm (brown-
black-brown).
31. Identify the remaining small signal transistors Q1, Q2, Q3, Q4 (three
leads marked 3904). Notice that there is a "flat" side of the component.
Install these transistors, being sure to mount the flat side as shown in the
parts diagram. These transistor are the drivers for the relays, they
provides enough current to energized the relay coil.
32. Install the remaining 1N4002 diodes in the D1, D2, D3, and D4
positions. Yep, you remembered, those diodes are polarized so that the
banded end must face in the direction shown in the parts diagram.
But wait, the relays run on an applied DC voltage, and the diodes are not used
"in series" like we did before (on step 5) . . . what is their purpose? Well, a
relay employs a large coil of wire to generate its magnetic field, so the energy
is stored in the field. When the relay is abruptly shut off, the field collapses
and a counter EMF is produced causing an inductive voltage spike. The diode
limits this to a small voltage, protecting the relay coil and any component
"upstream" of it. Its is always a good design practice to include it, and you will
almost always see one across the coil of a DC relay.
33. Carefully position and install relays K1, K2, K3, and K4. Note that the
pins are offset such that the component will only fit one way. Use care to
ensure that all four leads protrude through the circuit board before
soldering.
34. On to the last component the infrared detector. Depending on the
vendor for this component, you may have received one that contains three
mounting pins "in line" or one with offset pins Either will work, and they
perform exactly the same, it is just a question of which was "in stock" at
the time we placed our order. In either case, the detector is positioned
such that the "bump" on the package is facing out, and the part should
NOT be placed flat on the board. The component should actually be
positioned about 3/4" (~20 mm) above the board so that it "looks" through
the opening in the pre punched panel.
CONGRATULATIONS !
Your Remote Control Interface kit is now complete! Have a final look over
your work, paying particular attention to the orientation of diodes, capacitors,
and IC's. Remember that any problems you find now can save time and effort
after the unit has been cased up and final assembled.
ICI1 Page 16
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