For home circuit diagrams

Courtesy Light

15 seconds delayed switch-off. A good idea for bedroom lamps

Doorbell Warning Switch

This circuit will light a lamp at a remote location when the doorbell switch is pressed. This circuit should only be used with the solenoid type doorbells, the electronic type that play tunes will not work here.

Self-powered Door-bell Watcher

Detects if the door-bell has rung in your absence Also suitable for different electric appliances

Digital Combination Lock

A multiple input combination loack using CMOS counter IC's. Flexibility and code change is allowed by changing output connections.

Energy Leak Detector

High sensitivity, portable temperature comparator Detects draughts around doors, windows, etc.

Bells ring Generator

Three circuit options. Can be synchronized to Christmas tree flashing lights

Doorbell for the Deaf

This circuit provides a delayed visual indication when a door bell switch is pressed. In addition, a DPDT switch can be moved from within the house which will light a lamp in the door bell switch. The lamp can illuminate the words "Please Wait" for anyone with walking difficulties.

Cuckoo-song Generator

Agreeable, very close sound imitation. Suitable for sound effects, door-bells etc.

Electronic Door Release

The IC is a quad 2 input "AND" gate, a CMOS 4081. These gates only produce a HIGH output, when BOTH the inputs are HIGH. When the key wired to 'E' is pressed, current through R1 and D1 switchs Q5 on.The relay energises; and Q5 is 'latched on' by R8. Thus, the Alarm is set by pressing a single key,say one of the two non-numeric symbols.

Electronic Doorbell with Counter

This circuit uses a synthesized sound chip from Holtek, the HT-2811. This reproduces the sound of a "ding-dong" chiming doorbell. Additionally, the circuit includes a CMOS 4026 counter display driver IC to count your visitors.