Dark Activated Switch | Electronic Project Circuits

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Dark Activated Terrace Lamp

Compact circuit, Can be wired in parallel to existing switches
This device allows one or more lamps to illuminate at sunset and turn off at dawn.Q1 and Q2 form a trigger device for the SCR, providing short pulses at 100Hz frequency. Pulse duration is set by R2 and C1.When the light hits R1, the photo resistor assumes a very low resistance value, almost shorting C1 and preventing circuit operation. When R1 is in the dark, its resistance value becomes very high thus enabling circuit operation.
Parts:
R1 = LDR
R2 = 100K
R3 = 200K
R4 = 470R
R5 = 12K
R6 = 1K
R7 = 470R
C1 = 10nF-63V
D1 = TIC106D
D2 = 1N4007
D3 = 1N4007
D4 = 1N4007
D5 = 1N4007
Q1 = BD327
Q2 = BD337
SK1 = Female Mains Socket

Notes:
* R3 allows fine setting of operating threshold and R2 value can be raised to 150K maximum.
* Several lamps wired in parallel can be connected to the circuit, provided total power dissipation of the load does not exceed about 300 – 500W.
* PL1 can be omitted and the input mains supply wires connected in parallel to any switch controlling lamps. In this case, if the switch is left open, the circuit will be able to drive the lamps; if the switch is closed, the lamps will illuminate and the circuit will be by-passed.
* Warning! The circuit is connected to 230Vac mains, and then some parts in the circuit board are subjected to lethal potential! Avoid touching the circuit when plugged and enclose it in a plastic box.

Source: http://www.extremecircuits.net/2009/06/dark-activated-terrace-lamp_19.html

Be the first to comment - What do you think? Posted by admin - February 11, 2011 at 11:06 pm

Categories: Electronic Control, Lighting Tags: dark activated light, dark activated switch, sunlight activated switch

12V 10A Dark Activated Switch by LM324

The circuit is a combination manual switch and automatic dark-activated switch. It is designed to control up to 10 amps of 12V lights. A pair of high-intensity white LEDs are included in the circuit for built-in lighting. The circuit includes a low voltage disconnect circuit that prevents excessive battery discharge on battery operated systems. The DAS1 is ideal for solar powered lighting systems, it can also be used for line powered and automotive/marine applications. External 12V lights consisting of white LEDs, incandescent lamps and/or fluorescent lamps can be driven by this circuit.

Be the first to comment - What do you think? Posted by admin - October 3, 2007 at 1:03 pm

Categories: Electronic Control, Lighting Tags: automatic light control, dark activated switch, light switch, LM324 switch circuit

Dark Activated Switch by IC 741

This circuit will activate a relay when light falls to a preset level. Light level can be adjusted with VR1 and the relay contacts may be used to operate an external light or buzzer.

Notes:
The light sensor used is the ORP12 photocell. In bright light the resistance of the ORP12 can be as low as 80 ohm and at 50lux (darkness) the resistance increases to over 1 Mohm. The 1M control should provide a wide range for light intensities, if not its value may be increased. The op-amp senses the voltage difference between pins 2 and 3. The control VR1 is adjusted so that the relay is off, the output of the op-amp will be around 2 Volts. When light falls, the resistance of the photocell increases and the difference in input voltage is amplified by the op-amp, the output will swing towards full supply and drive the transistor and relay. The 270k resistor provides a small amount of hysteresis, so that the circuit switches on and off with slightly different light levels. This eliminates relay chatter. Take great care if you decide to wire the relay to activate a mains lamp. Make sure the relay contacts provide adequate isolation and have ample rating for the load.

Parts List:
ORP12 Photocell (1) RLY1: 12VSPDT (1) U1: UA741 (1) Q1: BC109 NPN (1) D1: 1N4002 DIODE (1) F1: 1A (1) VR1: 1M RESISTOR (1) ORP12: 500K RESISTOR (1) R1,R3,R2: 10k RESISTOR (3) R5: 4.7k RESISTOR (1) R6: 1k RESISTOR (1) R4: 270k RESISTOR (1)

Circuit : Andy Collinson
Email: anc@mitedu.freeserve.co.uk
Source :: http://www.zen22142.zen.co.uk/Circuits/Switching/darksw.htm