■ FIGURE 14. Breadboard battery in use.
■ FIGURE 15. Arduino proto shield alarm clock project.
alarm clock project shown in Figure 14.
AN ARDUINO ALARM CLOCK
Let's say we take all we've learned recently about
Fritzing and real time clocks, and build an Arduino alarm
clock like the one back in Figure 2. This is far cooler than
an ordinary alarm clock because it can talk to a PC over
the Arduino USB port. This allows us to set the time with
great accuracy from Internet sources, and it lets us set up
alarms using a PC terminal interface (instead of a few
buttons like you'd see on a regular alarm clock).
First, we will build the circuit on the mini breadboard,
which is a great way to test that a prototype works. Once
we get it working, we will transfer all the parts and wires
to PCB pads that exactly duplicate the mini breadboard
connections — this will let us take the tested design on the
breadboard — which isn't all that robust — and move it to
a PCB which is very robust. By robust, I mean how the
circuit will handle being jostled around or dropped.
The breadboard will allow parts to come loose, but
the PCB will have the parts firmly soldered down and be
much more resistant to being thrown about. We will
continue this into next month’s Workshop. (If you want to
follow along, you can get all the components shown in
Figure 15 and listed in Table 1 in a kit from the Nuts &
Two proto shield PCBs
One mini breadboard
Four-pin female header
10-pin shield header
Eight-pin shield header
Six-pin shield header
10-pin male header
Eight-pin male header
Six-pin male header
One DS1307 RTC IC
One 32.768 kHz watch crystal
One breadboard battery PCB
One battery holder 12 mm coin
One battery CR1220
One two-pin 90 degree male header
One capacitor 0.1 µF
Two resistors 2.2K ohm
One 10K ohm pull-up resistor
One piezo buzzer
Two feet of uncut jumper wire
Table 1. Bill of Materials.