found that the
height of the
header was tall
enough that I
could install it
and then flip the
board over so
the weight of
the board held
the header in
place. I soldered
one pin at a time and could see they were not
exactly straight. Because I only soldered one
side, I could heat the solder with one hand on
the soldering iron and
straighten the pins with the
other hand by touching the
second unsoldered cold pin.
When I got the pin to where
I wanted it, I let the solder
cool and held it in place.
When all the headers were
straight, I went back and
finished soldering the second
pin. Figures 4 and
this. If you look at the
schematic for the demo
board, you will see a jumper
5 that feeds power to the
switch and the potentiometer. You could add a jumper to
that connection in the same way we did with the LEDs,
but I never needed that so I left them connected. Instead,
I added a 2-pin header to the power connection shown in
Figure 6. This enabled me to easily connect a battery pack
to the board for external power.
There are battery modules with built-in step-up
regulators that give you a 5V output with a single AA
battery. They connect nicely to the board. Figure 7 shows
the battery holder I refer to. I used one in the golf cart
project from my May ‘09 column.
The 10-pin headers are the next item to install. I did
the same trick of installing them and then flipping the
board over to hold it while I soldered one pin. Figure 8
shows the first header installed.
■ FIGURE 3A
■ FIGURE 4. Header pins positioned
■ FIGURE 5. Final soldering of headers.
I could have placed the header in any one of the
three positions next to the 20-pin socket but this seemed
like a good spot since I would later be plugging in a
stacking board, which I’ll describe in a little bit. I added
the second 10-pin header and then moved on to placing
Figure 9 shows that the small breadboard has a
double-sided tape backing that just requires you to peel
off the protection layer. Before I removed the layer,
however, I practiced placing the breadboard on the circuit
board to make sure it would fit. The capacitor just above
the potentiometer may need to be bent back a little to
make it fit properly. Once you are ready, peel the
backing and stick it to the board (see Figure 10). The
double-sided tape holds well, so it isn’t going to budge
■ FIGURE 6. Power connection.
■ FIGURE 7. AA battery holder with
5V step-up circuitry.
■ FIGURE 8. 10-pin header installed.
July 2009 69