I've been working on experiment 15, and have run into some problems. I completed the first part with no problems and everything worked fine. When I added the switches and put everything into the box though, something must have gone wrong. The pushbutton works fine, and turns the green light on when it is supposed to. When I arm the alarm by flipping the toggle switch, the red light turns on like it should, but the siren/alarm activates instantly. Any ideas as to what is going on?
Also, not sure if this is relevant, but my power plug is getting very hot very quickly.
Your alarm is tripped from the start, check your wiring to the sensor switch. If you power supply can handle the load of the alarm and is still getting very hot, there could be a short somewhere, which might be why the alarm trips instantly. Make sure your sensor switch is closed when activating the alarm.
This is actually one of my favorite projects from the book. I have added red and blue flashing lights (for psychological effect)along with the buzzer. And a 555 timer (selectable)delay for the arming of the alarm so you can set the alarm and exit the house. Also a 555 timer to delay(selectable) the alarm activating so you can enter the house and deactivate the alarm before it goes off. And added the keypad security circuit described in the books projects. Next I want to add an Arduino and ethernet shield so it can tweet you if needed.