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CIRCUIT DESCRIPTION - DIGITAL SECTION
THE DATA SWITCHES
There are eight data switches labeled SW1 through SW8. The circuit is very simple. To perform the desired
functions, there is a double throw double pole switch, wired as a single pole double throw. One end is connected
to the 5V, the other to ground and the center lug is connected to the output.
THE LOGIC SWITCHES
The logic switches are also DPDT switches wired as SPST switches. The logic switches perform the same
function as the data switches. That is, they produce high or low states. But there is one big difference. When
switching the data switches, many pulses may be produced due to bouncing of the contacts.
In the logic switches, only one pulse is produced at the IC output no matter
haw many times the contacts bounce. This is extremely important if you
are producing pulses for counting circuits. Figure BB shows the wiring of
the logic switch. The two NAND gates are connected so that when the X
input is grounded, the X output goes high.
Opening and closing the
ground at X will not change the output. Only when X is grounded will the
output change to low. Thus, only one output change is produced with one
movement of the X switch. There are two outputs from each logic switch.
There are two outputs from each logic switch, X and X or Y and Y.
THE LOGIC INDICATORS
There are eight logic indicators. Figure CC shows the circuit. It consists
of a 74HC04 IC. When the input is over 2.8V, the output of the IC will be
low, drawing current through the LED indicator. The 120
Ω
resistor limits
the current in the LED to less than 20mA. When there is no connection to
the input of the logic indicators, the two 100k
Ω
resistor bias the input to
GND. This insures that the LED will be off.
TRAINER CASE CONVERSION
After using your trainer for educational purposes, you can convert your trainer into a tool case by removing the
trainer from the case. There are four plastic hole plugs included for the conversion. Simply unscrew and remove
the trainer from the case, and stick the plugs into the four hole locations shown. Then, insert the dividers in the
locations you desire.
Figure BB
Figure CC
Plastic Plug
Bottom View of Case
Plugs
