•  
  •  

DayLight Alarm

The circuit presented here wakes you up with a loud alarm at the break of the daylight. Once again the 555 timer is used here. It is working as an astable multivibrator at a frequency of about 1kHz.
The circuit’s operation can be explained as follows:

When no light falls on the LDR, the transistor is pulled high by the variable resistor. Hence the transistor is OFF and the reset pin of the 555 is pulled low. Due the this the 555 is reset.
When light falls on the LDR, its resistance decreases and pulls the base of the transistor low hence turning it ON. This pulls the reset pin 4 of the 555 high and hence enables the 555 oscillator and a sound is produced by the speaker.

The variable 100K resistor has to be adjusted to set the light intensity that triggers the alarm.

If there are any problems please contact webmaster@electronic-circuits-diagrams.com

Please share & like


K-type Thermocouple Sensor High Temperature Stainless Steel Insertion Probe HT02 picture

K-type Thermocouple Sensor High Temperature Stainless Steel Insertion Probe HT02

$12.99



1M K Type Thermocouple Sensor Digital Thermometer Temperature Meter TK80 4JPL8 picture

1M K Type Thermocouple Sensor Digital Thermometer Temperature Meter TK80 4JPL8

$7.29



1M K Type Thermocouple - Sensor Digital Thermometer Temperature Meter TK80 4JPL8 picture

1M K Type Thermocouple - Sensor Digital Thermometer Temperature Meter TK80 4JPL8

$10.99



2PCS K-Type Thermocouple Probe High Temperature Sensor Thermistor Probe K T 1M picture

2PCS K-Type Thermocouple Probe High Temperature Sensor Thermistor Probe K T 1M

$14.99



Fluke 80BK-A Type K Thermocouple, Temperature Bead Probe, Clamp - Multimeter.  picture

Fluke 80BK-A Type K Thermocouple, Temperature Bead Probe, Clamp - Multimeter.

$15.99



Heat-resistant K Type Stainless Steel Thermocouple Sensor 5mm Probe Meter picture

Heat-resistant K Type Stainless Steel Thermocouple Sensor 5mm Probe Meter

$8.39



Temp Thermocouple K type, stainless Steel Probe, 12 ft (3.66M), Teflon sealed picture

Temp Thermocouple K type, stainless Steel Probe, 12 ft (3.66M), Teflon sealed

$14.00



TM-902C Digital LCD Thermometer Meter Single Input K Type w/Thermocouple Probe# picture

TM-902C Digital LCD Thermometer Meter Single Input K Type w/Thermocouple Probe#

$13.95



US NEW High Temperature Type K Thermocouple Core Ceramic Kiln Probe 2372°F picture

US NEW High Temperature Type K Thermocouple Core Ceramic Kiln Probe 2372°F

$9.99



K-Type Thermocouple Probe Digital Thermometer Steel Sensor Spiral Cable  picture

K-Type Thermocouple Probe Digital Thermometer Steel Sensor Spiral Cable

$8.99