Five years ago one of my friends purchased a garage with a cellar and worried about how and what to do to potatoes and other vegetables, planted for winter storage in the cellar, didn’t freeze? Remember, rescued his once-popular thermostat through a balanced bridge with the two thermistors. And recently another friend of mine, being in the same life situation, asked me to help him in the manufacture of such devices.
Blind copying of someone else’s, although quite efficient, the device is not for me. And a number of considerations led to modernization of the basic thermostat.
First of all, I was not satisfied with that power supply the original variant was carried out according to the so-called transformerless scheme, where the nodes and elements under phase hazardous live voltage. After all, it is not excluded in the cellar water seepage. And the owner of the store vegetables, for example, in the roads could easily get his feet wet. What if he for a moment will affect the running of the thermostat? This helped to frame the main requirement to the thermostat: reliable isolation of the structure from the mains voltage, for example, by using separation or step-down transformer and the Executive relay.
Did not suit me, and the low-power device prototype with the radiant load in the form of 100-watt incandescent bulbs. Of course, in the upgraded design must operate heater with a capacity of not less than 1.5 kW in combination with a fan. If necessary, you can use it for quick drying cellars-greenhouses.