Nocturnal Animals Whisker

A low-rate flashing lamp drives away undesired visitors

Automatic on-off operation

Circuit diagram:

Animals Whisker


R1____________100K   1/4W Resistor
R2______________2M2  1/4W Resistor
R3_____________10K   1/4W Resistor (see Notes)
R4______________4K7  1/4W Resistor
R5____________Photo resistor (any type, see Notes)

C1,C2,C3_______47µF  25V Electrolytic Capacitors

D1___________1N4148  75V 150mA Diode

IC1____________7555 or TS555CN CMos Timer IC

Q1____________BD681  100V 4A NPN Darlington Transistor

LP1____________6V 3W Bulb (see Notes)

SW1____________SPST Switch

B1_____________6V 1.2A Lead acid sealed rechargeable Battery (see Notes)

Device purpose:

This circuit has proved very useful in keeping away from a terrace or a porch some bats and other nocturnal animals. You can use it for similar or different purposes. The lamp illuminates for a 4-5 seconds delay and stays off about one minute and 15 seconds. The photo resistor allows automatic switch-on of the circuit at dusk and switch-off at dawn. Supposing an eight hours operation per night, the lamp stays on for a total of about 30 minutes, allowing great current economy.

Circuit operation:

IC1 is wired as an astable multivibrator with on and off time-delays as explained before. R1 & C1 set the on time-delay, R2 & C1 set the off time-delay. As there is no critical parameter, you can set these delays at your wish. Q1 is the lamp driver and can feed rather big bulbs. C2 prevents some brief instability when voltage at pin 4 of IC1 is very close to switching threshold.