Light Dark Detector Circuit | Electronic Project Circuits

Posts Tagged ‘light dark detector circuit’

Dark Activated Led or Lamp Flasher

Simple photo-sensitive circuit, 3V battery supply

This circuit adopts the rather unusual Bowes/White emitter coupled multivibrator circuit. The oscillation frequency is about 1Hz and is set by C1 value. The LED starts flashing when the photo resistor is scarcely illuminated. The onset of flashing can be set by trimming R2.

Parts:
R1 = LDR
R2 = 100K
R3 = 10K
R5 = 470R
R6 = 47R
R4 = 10K
C1 = 220uF-25V
D1 = 1N4148
D2 = LED any type (see notes)
Q1 = BC337
Q2 = BC337
B1 = 3V Battery or 2×1.5V cells in series
SW1 = SPST Switch

Notes:
* Best results in flashing frequency can be obtained using for C1 a value in the 100 – 1000µF ranges.
* To drive a filament lamp make the following changes:
* Use a 2.2 to 3V, 250-300mA bulb in place of the LED
* R2 = 10K 1/2W Trimmer Cermet
* R3, R4 = 1K 1/4W Resistors
* R6 = 1R 1/4W Resistor
* C1 = 470 to 1000µF 25V Electrolytic Capacitor
* In LED-mode operation the stand-by current consumption is less than 400µA.
* In Lamp-mode operation the stand-by current consumption is about 3mA.

Source : www.redcircuits.com

Be the first to comment - What do you think? Posted by admin - February 12, 2011 at 8:30 pm

Categories: Electronic Control, Lighting Tags: automatic night lamp, dark activated led, light dark detector circuit

Simple Darkness Activated Alarm by IC 555

Most darkness activated alarms employ opamps and some logic ICs. Here, a less expensive approach is shown based on the eternal 555, this time in monostable multivibrator mode. Components R2 and C1 represent a one-second network. When the LDR (light dependent resistor) is in the dark, its resistance is high, pulling pin 2 of the 555 to ground. This triggers the monostable and the (active!) 6-volt piezo buzzer will sound. Preset P1 is adjusted depending on ambient light levels. The circuit may be fitted on a wall in your home. Assuming P1 has been set for the existing ambient light level, the shadow cast by anybody entering the room or hallway will trigger the alarm.
Author: Myo Min – Copyright: Elektor July-August 2004
Source: http://www.extremecircuits.net/

Be the first to comment - What do you think? Posted by admin - August 11, 2010 at 7:22 am

Categories: Alarm systems, Lighting Tags: light alarm circuit, light dark detector circuit

Active light control by LDR and BC337

This is automatic light circuit when be become dark. It by use LED Lamp, be a place gives the light and this circuit has small-sized use volt supply 3V only.

The work of the circuit be when there is the light affects LDR1 will valuable the resistance at LDR1. It be down make Q1 work be born volt at fall straddle a pin C of Q1 compare with Ground be valuable a little more voltage bias to make Q2 work. By have D1 serial with a pin B of Q2 make volt at pin C of Q1 compare with ground must use volt about 1.4V arrive at make Q2 work. But when LDR1 no the light will make to is valuable the resistance more and more until make to have no current flow get along well with B of Q1 make Q1 do not work. Then have current flow through R1,D1 get along well with pin B of Q2 work cause LED1 stick bright. The part , VR1 , parallel connection with , LDR1 , as a result , for take keep fine the rapidity in taking light of LDR1