■ FIGURE 6. Pill timers.
square pad and
the thru-hole is
the same as
before, then it
should still be
easy to solder a
would allow port GP3 to be used as an input for such
things as trigger or gating signals. This port pin already has
a pull-up resistor, so connecting input signals would be
really easy. This input would allow the pill timer to be used
for one shot applications, using the basic components in
the provided programs to write a new program. Even
without the thru-hole, a wire can be carefully soldered to
the present pad to give an input signal.
■ FIGURE 7. Size reference of pill timer.
Building the Pill Timer
damaging the actual circuit board. That’s why the single
board design is included, so you can copy and paste it
into a multi-board design with sufficient spacing to cut
everything out. That is, have the width of the cutter blade
between each circuit board.
Note that these prices are for circuit boards without
the silkscreen and solder mask, and while useable, great
care must be taken when soldering parts on. I ordered my
three boards with the silkscreen and solder mask so the
cost was $86 for three boards, making the cost per board
about a dollar each. (Not bad for high quality circuit
boards, except it may take you a while to use 87 of them.)
Although I didn’t make any improvements to the
circuit board layout, there are two things that I would now
do differently. First, I’d make the three holes for
connecting the ICD a little larger to make connections
easier. Second, the lower pad of JP1 would be a thru-hole
the same size as used to mount the lead wires. If the gap
■ FIGURE 8. Circuit board layout.
The downside to building pill timers is it’s all surface-mount technology. However, if you haven’t done a project
with surface-mount components, then this will be a nice
little project to start with. Since the gap between pads for
the PIC10F200 is only about 0.024 inches; you will need a
needle-point tip for your soldering iron. This part is the
most difficult to solder in-circuit because it’s easy to get a
solder bridge between the microprocessor’s pins. The
remaining parts are large enough and there is sufficient
spacing that soldering is easy.
When soldering surface-mount parts, I find it’s best to
glue each part in place, so there isn’t any slipping around
while trying to hold your soldering iron in one hand and
the solder in the other. (Commercial fabricators glue the
parts down prior to soldering.) I use a two-part epoxy
called J-B Weld (part number 8265-S) found in most
hardware and auto supply stores. This stuff can be used to
repair an engine block, so it doesn’t have problems with
heat. To use, I mix just a dab, then use a toothpick to
place just a pin point of glue where the component goes.
Then using tweezers, I place the component on the glue
spot where it will be soldered. The glue needs to set
several hours before soldering; I usually wait
overnight. Don’t use so much glue that it
squeezes out and covers the surfaces to be
soldered, since that will prevent the solder from
making electrical contact.
Once the parts are soldered on, connect
the programmer adapter and PICkit 2
programmer to the pill timer and download the
program to the microprocessor. Now, solder on
your lead wires and add it to your project.
So, what can you do with your pill timer?