Twilight Switch
This circuit lights an electric bulb in darkness.
Update October 2008
It has been about 3.5 years since I designed and built this circuit, but I never managed to fill in the component values. In October 2008, I updated the circuit and calculated the components again. Sensitivity can be controlled using R4.
Schematic
| Name | Comment |
|---|---|
| twilight-switch.sch | Source file for gschem. |
Parts
| R1 | Photoresistor LDR03 (0.1kΩ-2kΩ lit, 1MΩ-100MΩ dark) |
| R2 | 2.2kΩ |
| R3 | 220Ω |
| R4 | Potentiometer, 10kΩ |
| R5 | 680Ω |
| Q1 | BC547B |
| Q2 | BC368 |
| U1 | 74L14 (Schmitt trigger) |
| T1..2 | Terminals for electric bulb, 6V/2.4W |