Freezer Alarm
Approx construction cost US$19
If the problem is not spotted in time, the likely result is a great deal of wasted food. Unfortunately, unless smoke starts to pour out the back of the freezer, it is unlikely that the problem will be noticed until the food has defrosted and you are confronted with a soggy mess.
This very simple alarm project provides an early warning of problems by sounding an audible alarm if the temperature inside the freezer rises above a preset threshold level. The user is alerted to the fault long before the food has a chance to defrost, and hopefully in time to get the problem fixed before the food is ruined.
The circuit is battery powered and is therefore immune to failure of the mains supply. Although the unit must be left running continuously, the current consumption has been kept to a very low level that ensures each set of batteries has virtually its "shelf" life.
More details on this construction project can be found in the August 1999 issue of EPE Online, the world's first web-delivered electronics and computing hobbyist magazine.
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