Very often the inhabitants of the city apartments there is a problem with the storage of potatoes. In winter, the best place on the balcony or loggia, is not found even in the presence of the pantry. In the pantry, and even in multi-storey basement under the house (many tested on their own experience) too warm, and the potatoes after storing, it begins to sprout.
The balcony in this respect a great advantage. But one cannot do without the thermostat. I want to share with the readers of the magazine "Radio Amateur" is a well proven device. For the past five winters, in addition to the replacement of one of two light bulbs, it did not cause any trouble, securely covering the tubers from frost outside the window of my apartment.
Wiring diagram I borrowed from E. Babynin (see "M-K", 8/1985). Else " "fantasy on the free theme".
The thermostat is a drawer with double-skinned, 40-mm space between them on the sides is filled with shredded foam from a variety of packages. Good smooth foam sheets are useful for uteplenija cover. Their glue so that the foam covers included inside the outer double side walls and rested on the inner wall. The inner wall height is made lower external in order to ensure a tight fit of the lid, (see Fig.1). If a good seal to be achieved - not a problem. In this case, glue on the edges of the lid foam.
Fig.1
Internal the bottom of the thermostat freely inserted inside the box. Bottom nailed to the bottom of the several supporting bars thickness 20 - 30 mm in the Middle and the top is attached to the bottom of the tube made of thin tin, chosen so as to be able to put light bulbs that are used as heating elements. If the tin on hand will not be in the business can go pruning old ventilation pipes. In the bottom under the pipe to drill some vent holes diameter 8...10 mm.
After you install the bottom attached to a pipe it must be ensured that the pipe was located approximately 20 mm below the internal walls of the box. This design thermostat allows heated in the pipe air to circulate freely throughout the volume of our mini-storage blower almost every tuber.
The thermostat housing is easy to manufacture from readily available materials, for example, from scraps of chipboard or thin boards. The side exterior walls, it is desirable to do with the tabs at the bottom as legs so that the bottom is not in contact with the cold concrete floor of Your balcony. Dimensions thermostat - reference, if desired, they can be reduce or increase, adjusting to the size of the balcony and the volume allocated for the storage of potatoes. The dimensions shown in Fig. 1 thermostat - HH.
Fig.2
In Fig. 2 shows the electrical circuit of the thermostat the thermostat. As the heating element it uses two incandescent lamp (220V, 60W) is placed, as mentioned above, in the pipe. The heating element included in the circuit of thyristor V5. Elements thermostats are supplied from a stabilized power supply (V10, S1, R1). Upon cooling, the temperature sensor, which is made on the thermistor R4, its resistance increases, and thus the potential at the base of V9 is reduced to until the transistor V8, V9 are closed. Once closed V8, V9, the current flowing through R2, R5 opens the transistor V6 and the associated thyristor V5. The heater will work until then, until the temperature at the location of the temperature sensor reaches this value at which the resistance drops and he opens the transistors V8 V9. The transistor V6 and the thyristor V5 is closed and the process repeats itself until the establishment of the dynamic mode equilibrium.
Thermal overload relay can be assembled on any transistors with sufficiently high ( 50) gain. Diodes D and the thyristor KU selected for durability. However, when changing to other item types, remember that they are used in the calculation of the line current of 3A and a reverse voltage 400...600 V. the Thyristor also should be selected based on forward voltage not less than 400 V. When using the specified capacity of the heater and types of diode rectifier and thyristor, the radiator can not be installed. The thermistor need for precautions to be put in a protective shell (e.g., in a tube from a used pen).
For the convenience of monitoring the operation of the thermostat after the fuse, put a neon bulb, which will provide evidence of the condition of the fuse. In addition, in series in the load circuit may include a shunt and parallel to it to connect a microammeter. Shunt resistance should be selected so that when fully open thyristor arrow microammeter deviated to the full scale. As a micro-ammeter shunt For 100 μa and below seems to work piece installation of wire of a suitable length. Then the value of deflection of the microammeter installed in any convenient location, it will be possible to judge the thermostat and the need to "replace burned out light bulbs.
The device requires no adjustment, except for setting the desired temperature. The temperature inside the thermostat should be 0...4 s. This value is optimal for storage of potatoes. Usually when these dimensions thermostat fluctuations range 1...2 s. the Temperature set resistor R7. The sensor is placed on the surface of the potatoes.
By that time, when will this issue, the court will already be spring, and the theme of the potato to someone may seem irrelevant. And yet, I would advise not to throw out the description of the thermostat. Come autumn, this simple design will help You out.
Author: Belsky; Publication: N. Bolshakov, rf.atnn.ru