30 June 2015
It has two bi-colored LEDs that change from red to
green, depending on how the two leads are powered from
five volts to ground. Reversing the LEDs causes the colors
to change. They normally should be green.
If the receiver receives an alarm transmission, it turns
on the piezo buzzer which squeals. This can be silenced by
pushing a reset switch.
As with most projects, there are obstacles. This
one was no exception. I had ordered boards, started
programming, and was going to use a multiplexing scheme
n FIGURE 1. Transmitter box. n FIGURE 2. Transmitter board. n FIGURE 3. Battery holders.