Energy regulation circuit - help please

peterlonz 20 years ago

Hi,

I have a project in mind that requires the switching on & off of a domestic refrigerator. The purpose is to control the internal fridge temperature at a level suitable for brewing lager beer. The highest setting available on fridges is of course too low & would stop fermentation.

My idea is to provide an adjustable (timer controlled?) circuit that would operate a relay & allow switching "on" for say 30mins & then "off " for say

60 mins. This should allow the desired temperature of 18 to 20 Deg C to be achieved with a little trial & error.

Can anyone oblige by helping me with a simple circuit preferably made from easily purchased low cost components.

Thanks Pete

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gfretwell 20 years ago

You could probably do this with a regular air conditioner thermostat and a relay. Put the 'stat in the fridge and feed the fridge power through the relay.

Alternately you can make a pretty good thermostat with a thermister and a whetstone bridge, feeding a 741 Op Amp, picking a relay.

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Andrew Gabriel 20 years ago

If you find the thermostat in the fridge, it will likely have a course adjustment screw on it, which you can turn to make the thermostat operate over a completely different temperature range. A bit of trial an error will be required to set it. If it's electronic, a trimmer adjustment or resistor change might achieve the same thing.

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SQLit 20 years ago

look for a "ice cube" timing relay. You will need to find one that is motor/current rated for your application, compressors on start up are 6 times the running amps.

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check Automation Direct, or Potter Brumfeild

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