152
This is the A-head
Part II: More Hacking Techniques
Next, take the second piece of perf board and install 18 20-pin IC sockets.
Leave room on the edges of the board for the connectors. The power for the
entire circuit board will come from an external PC-style power supply.
You will want to install the sockets in the board so that if any IC is incorrectly
wired and becomes damaged when you apply power to the circuit, you will not
have to resolder the part in place again. Just pop out the bad part and pop in a
replacement.
Connect all integrated circuits
Once all of the sockets have been soldered in place for the controller board,
you will need to connect them according to the schematic diagrams in
Exhibits E through M
.
This is a good time to check your work to ensure that everything is wired
properly. You should also check that the power and ground wire are not
shorted together by using a multi-meter to measure the resistance between
these two parts of the circuit. The meter should read infinite resistance (or
at least over 1 mega-Ohm) when you place the probes on these parts of the
circuits.
Lay out your circuit according to the diagram in
Figure 8-2
. Connector P7
connects to a PC parallel port. Connectors J1 through J9 and J11 through
J13 are optional. They can be used to connect the Shift Register (
Exhibit
K
) and LED Driver Connectors circuits (
Exhibits E through J
) to the LED
Buffers circuit if you build them on two separate boards. If you place all of
the chips on one board, these connectors are not required. If the circuits are
separated, ensure that the ribbon cable used to connect them is no longer
than six inches in length.
Figure 8-2: Small-scale system board overview
J7
J8
J9 J11
J12 J13
P7
J10
Miniblinkenlights shift registers
and LED driver connectors
DB25 connector to
PC parallel port
Power connector
P1
P2
P3
P4
P5
P6
J11
LED buffers
J1
J2
J3
J4
J5
J6
If two boards are built, use ribbon
cables to connect between these
two boards
Power connector
To LEDs