Instructables

I want an alarm to go off if the freezer door is open for 5 minutes or more.?

Our freezer door keeps getting left open, so I want to install an alarm that will go off if it stays open for 5 minutes or more.  I don't just want an open door alarm, than would be annoying when loading/unloading the freezer.
One that would shock the offending child would be an added bonus but not needed.

iceng2 years ago
List of ezy sensors for Freezer door ;
  1. Light On detect
  2. Temperature raise
  3. Magnet & reed Switch
  4. Micro-switch
  5. Voltage to internal light
  6. Pressure pop
  7. Weight shift
  8. Smart self close freezer
  9. House elf
  10. Intelligent family
A
Okay Burf, since you've opened it up to fridge alarms...

Redcircuits.com's award winning original design and the improved design. Leave the guts outside the freezer with just the sensor on the inside, probably connected with a thin twisted pair. Follow the individual descriptions for what to change in order to increase the timeout period.

As an alternative to a LDR, you can use a N.C. (normally closed) magnetic reed switch and a magnet together with a 220K ohm resistor across the contacts and a 1.5K ohm resistor in series with the reed switch to simulate the LDR. Door closed means switch is open, 220K + 1.5K = 221.5K - circuit ready, but quiet. Door open means switch shorts the leads of the 220K, effectively removing it from the circuit, leaving only the 1.5K in line, thereby turning the ciruit "on" and counting.Closing the door puts the 220K back in turning the circuit back "off". This would keep everything outside the freezer, free of the effects of any cold.

Qa
Burf2 years ago
Here is a page that shows how to build a refrigerator open door alarm.

www.extremecircuits.net/2010/03/fridge-door-open-alarm-circuit-project.html

Or you can search google for 'refrigerator open door alarms' for a ready to install unit.
iceng Burf2 years ago
+1
jeff-o2 years ago
The easiest way would be using a 555 timer. This might help: http://home.cogeco.ca/~rpaisley4/LM555.html#20
rickharris2 years ago
For easy approach this is a micro controller project see www.picaxe.com

HOWEVER

A micro switch could trigger a 555 timer to trigger an alarm.