LDR Pole Light Switch


Posted on Feb 5, 2014

My vintage (62 year old) pole light has always been controlled by a timer ”a source of continual frustration due the requirement of readjustment for the ever-changing seasons. However, after knocking it over (I backed my car into it ), I decided it was time for an update. The circuit consists of a light dependent resistor (LDR), TLC555 (applied


LDR Pole Light Switch
Click here to download the full size of the above Circuit.

as Schmitt trigger), and a TRIAC power switch. The complete assembly neatly fits inside the steel pole light tube and the LDR peeks out through a hole in the side. This was really a fun project, and useful to boot. The power supply is the typical capacitor limited charge pump type that is zener regulated at 6. 2V. Due to the lack of isolation, I was careful to identify the return conductor so that the electronics (including the LDR) would not be floating on the hot lead. For safety, most of the testing was done using an isolation transformer. R1 must absorb a high peak power transient current when power is applied, so a carbon comp, ceramic comp, or wire wound resistor is recommended. Maximum DC current available is 16mA. Actual load is about 6mA. My application was 115V, 60hZ. For 230VAC, the components are indicated on the schematic. In this circuit, +6V is the power return lead, and 0V is the electronic circuit common ”to visualize this, one must screw his head on backwards The light dependent resistor (CdS photocell) that I used was in the TO-5 package that is well adapted for poking through a hole and is held in place with silicone rubber. The Clairex CL703M19 LDR that I used is no longer available and I have been unable to locate the specs. The DigiKey PDV-P8103-ND appears to be a reasonable choice, but may require bias current tweaking to set the threshold. A TLC 555 was used as a voltage threshold detecting device...




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

FM Transmitter (2N2222)
3V Lamp Brightness Controller circuit diagram
Flash programming of AT89 microcontrollers using ISP adapter
LED Audio Level Meter Circuit Schematic Diagram
Fun Game Circuits
led blinking program with pic16f887
build your own geiger counter
Battery Charger Regulator
IR On/Off Switch Using Microcontroller
Ultra-Sonic Ranging Design
Synchronous RS flip-flop circuit structure and symbols
Monitor circuit diagram with over 555



Top