Sheet 1
Light Dependant Nest Box Lighting karl grabe 1.0 CorkNest.com 1 of 1 1 28 May 2008
-10 0 400 0 0 0 0 Arial -13 6 400 0 0 0 0 Arial -13 6 400 0 0 0 0 Arial -13 6 400 0 0 0 0 Arial -43 13 400 0 0 0 0 Arial -23 11 400 0 0 0 0 Arial -23 6 400 0 0 0 0 Arial -16 7 400 0 0 0 0 Arial 000000 1 000000 1 000000 1 000000 1 -1 000000 NE555 U? Alternate 555 Timer 1 $$SPICE_PROLOG_PRIORITY 5 000002 0,0 $$SPICE_EPILOG_PRIORITY 5 000002 0,0 Package package name for PCB layout 000001 0,0 Dis Thr CV V+ Res Gnd Tr Out C C? Capacitor 1 JO J? Connection Output 1 POT R? Variable Resistor 1 adj a b LDR R? LDR 1 $$SPICE_PROLOG_PRIORITY 5 000002 0,0 $$SPICE_EPILOG_PRIORITY 5 000002 0,0 Package package name for PCB layout 000001 0,0 LED Resistor LED? LED Resistor 1 $$SPICE_PROLOG_PRIORITY 5 000002 0,0 $$SPICE_EPILOG_PRIORITY 5 000002 0,0 Package package name for PCB layout 000001 0,0 1 0 FF0000 0000FF 000000 000000 208000 000000 4040C0 208020 FFFFFF GND 1 or more 12V LEDs in the nest box Total Current < 200mA (NE555 limit) Notes The NE555 is used in Schmidt trigger mode. At dawn the resistance of LDR 1 drops as the outside light intensifies. When the voltage at NE555 pins 2&6 drops below 1/3 of 12volt pin 3 and 7 drop low lighing both the Lights on indicater (LED 2) and the LEDs in the nestbox. Adjust VR1 so that the lights come on and off at the desired levels. There is hystersis - Lights on at 1/3 12V at pins 2&6 and off at 2/3 12V at pins 2&6 so the lights won't flicker on an off if the outside light varys by a small amount. At dusk LDR1's resistance rises and when the voltage at pins 2&6 reaches 2/3 of 12 Volts then the pins 3 goes high and 7 goes open circuit switching off the LEDs. NE555 Timer pin 7 is normally used to discharge a timing capacitor but here is used to drive status LED 2 to show the lights are on in the nest box. C1 helps prevend disturbance by electical noise, but it can be ommitted. LED 1 is always on, indicating that the circuit is powered. The supply voltage can be increased to about 14 volt, to allow for pin 3 voltage drops. The nest box LEDS are 12V-LED 5mm white 6000mcd available from LED1.de (and other sources)