THERMOSTAT FOR VEGETABLES

THERMOSTAT FOR VEGETABLESRead the article A. Christmas “Cellar, on the balcony” (“M-K” No. 2, 1984) and not all agreed with the author. He applied heater power of 500 watts. This implies that the air circulating in the container, probably heated above the put — 2°C. In such conditions, the vegetables and the walls misted and damp atmosphere decreases, and drastically, the reliability of the heating element. How maintained the required humidity design A. Christmas? It is not “breathing” hole, and it is necessary, especially when storing, say, cabbage or carrots. It is also important that the recommended sensor TUDA-1 to buy is quite difficult.

In its design I tried to address these shortcomings, and offer readers a description of the vegetable, which is used for three years.
 
The vault is a “thermos” of the two boxes. External in the form of a cube with sides of 750 mm, made of planks thickness of 15 mm, inner — 12 mm plywood. The space between them is filled with glass wool (you can use other insulation materials, pre-impregnated stain from rodents and insects: cotton, sawdust, shavings).
 
Cover of the boards connected at the top and bottom of the plywood sheets, covered on all sides with plastic wrap. The capacity for vegetables wrapped in foil only the outside (the coating material may be rubberized fabric, oilcloth, etc.).
Under the lid is a rubber seal with a gap of 25 mm breathing hole. In the front wall of the greenhouse with a slotted opening 100X75 mm emergency eject Heaters.
 
At the bottom of the inner box, in metal casings are located two series-connected electric heating element — heating element with a power of 300 watts each (photogenically). They are attached to the box out of sheet aluminum with a moisture-absorbing material (salt, sand), separated from the bottom of the porcelain insulators. Even higher on the bars, laid a lattice of wooden battens of section 50 X 25 mm, on which poured the vegetables.
 
Fig. 1. Device
 
Fig. 1. Device “thermos” (the front wall is conditionally withdrawn):
 
1 — outer box, 2 inner box, 3 — porcelain insulator, 4 — aluminium box section 5 — glass, 6 — boxes with heating coils, 7 — wood grille, 8 — mounting bars, a 9 — film coating, 10 — rubber seal, 11 — “breathing” hole, 12 — sand.

 
Fig. 2. Modification of the starter into the sensor
Fig. 2. Alteration starter in sensor:
 
1 is a bimetallic plate, 2 — pin stand, 3 — electrode, 4 — paper Cup.

 
R and p. 3. Schematic diagram of the Executive instrument.
 
R and S. 3. Schematic diagram of the Executive instrument.
 
Now, how manufactured temperature sensors to enable and disable the hardware Executive and hardware. As first used starters for fluorescent lamp. The starter is opened, and from it extracted the glass bulb breaker. 6 wrapping paper so as not to damage the pieces of hands and eyes, break it and remove the internal parts (Fig. 2).
 
Adjust the sensor as follows. Connecting it to the signal lamp and power source, placed in such place where it is maintained at a constant temperature of +2°C. On the thermometer monitor the temperature, and the resistance included in the circuit of the sensor — the time of operation. If necessary, adjust the gap between the contact bar and the bimetal plate. Similarly to produce a second sensor temperature + 4°C. Then glued to their bases paper cups, covering the post electrodes, and fill with epoxy.
 
When the sensors activate and deactivate ready, gather the Executive apparatus. It consists of two relays, the diode bridge rectifier and step-down transformer. Closing the circuit, the sensor B1 includes low-voltage relay K1, which contact plates K1.1 and K1.2 shunts itself activates a more powerful relay K2 with an amperage of 1.5—2 A. the Latter includes heating elements and lamp H2 control of their work. Upon reaching the desired temperature sensor B2 breaks the supply circuit of the relay K1 and therefore K2, and Heaters, and H2. Lamp H1 indicates the presence of voltage in a circuit actuator.
 
If there is a need to control the temperature in the vegetable store, you can build a bridge of resistors and place it as the sensor in the “thermos”, and the diagonal of the bridge to enter DC voltmeter with a scale of 1—MINUTE, scaled in degrees. Food — also from the transformer through a diode rectifier.
 
Network winding of the transformer contains 2,400 turns of wire of PEL 0,12; winding II — 60, 120 or 240 turns of wire PEL of 0.31, depending on the response voltage of the relay (6, 12 or 24V); III winding — 120 turns of the same wire.
 
Resistor R5 is selected depending on the voltage dumps H2.
 
We need to very carefully run the wire to the vegetable store. It should be laid in thin-walled, electrically grounded or “zeroed” tube or the metal hose and have reliable insulation.
 
I. YAKOVENKO, G. G o R l o V K a, Donetsk region.

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