Fridge's Door Warning (easy Schematic)

make an easy fridge's door warning with simple parts.

i use

• 555 timer
• 2N5551 trancistor
• 2x 1k resistors
• 170k resistor
• led
• 100uF capacitor (change this to change the delay)
• 0.1uF capacitor
• normanly open switch
• TMB12A12 beeper
• LRV08 12v battery

print the pcb with express pcb and drill the holes

solder all parts and test it

this circuit wait you about 25 seconds to close the fridge's door

paint the pcb with a color or lacquer spray to protect the copper

find a box for the project or download the .stl files and print them works with N O switch

put the pcb into the box and glue it with instant glue

add at the back of the box a two side tape

put the battery , the cover and its is ready

when the led is on the door is open and the battery is ok

if you close the door the (normanly open) swich, the circuit is turned off and you dont worry for the battery

the 555 needs 10 mA and the beeper needs 25 mA if the beeper turned on

if you like this project follow me !!

thanks