Also pay attention to the jumpers at R3 and R4 on the right-hand side of the diagram. R3 is an
optional resistor, to be fitted to enable in-circuit-programming for those wishing to update their own
firmware and having the necessary equipment.
If you do not fit a 100K resistor for R3, then you must fit a wire jumper here as shown.
Resistor R4 is an optional resistor, which is in series with the top of the contrast adjustment
potentiometer R1 and +5V. Typically the contrast voltage required is less than 1V and the
adjustment is rather sensitive. If you wish, you can fit a 220K resistor in this position, which will
make the contrast potentiometer less sensitive to adjust.
If you do not fit a 200K resistor for R4, then you must fit a wire jumper here as shown.
8)
Solder in transistors Q1 and Q2.
If you have purchased additional transistors
for Q3 and Q4 to increase the power output,
then Install these now too.
The transistors are located at the edge of the
PCB with their flat side outwards. This is to
allow easy attachment of a heatsink if desired (for higher voltage and hence higher power
operation).
9)
Install two 16-way connectors on the main PCB and LCD.
Either way is fine, but my recommendation for
installing the LCD connectors, is to use the
female (socket) connector on the PCB side
and the male (plug) on the LCD.
Be sure to
solder the socket to the reverse of the
main U3 PCB!! Not the top side!
If you bolt
together the LCD module and the PCB, with
the 16-way connectors in place but not
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