In the proposed device applied position control with Bespalova switching the load during the transition of the mains voltage through zero. In addition, its distinguishing feature - the ability to switch modes operation "Heating" or "Cooling"
The proposed thermal stabilizer in the winter will help to keep fruits and vegetables:
- on the balcony or loggia in a thermally insulated container with built-in heater;
- pantry, basement with commutator motor with fan, blowing cold outside air.
The regulator circuit shown in Fig. 1, and a drawing of the circuit Board in Fig. 2. The desired temperature set by the variable resistor R7. Device contains a switch that allows you to set the modes of cooling or heating.
The temperature sensor is a PTC resistor RK1. Nourish it from parametric stabilizer HL1R5. The sensor signal is amplified by the transistor VT2 and acts the inputs of the element DD1.2: elevated temperature corresponds to a high level at its output, and low - low. Resistor R9 provides some hysteresis of the sensor signal when the temperature changes that is needed for position regulation.
Further direct or inverted element DD1.3 the status signal of the sensor temperature goes on the bottom on the circuit input (pin 12) of the element matches DD1.4, on the upper input (pin 13) contains synchronization pulses, corresponding to the moments of transition of the mains voltage through zero. Only the presence voltage high level on the lower inlet allows the flow of governors pulses to the triac, so the "Heat" switch SA1 corresponds to the turning on of the triac, with decreasing temperature, and the position Cooling - if you increase. Led НL2 indicates operation of the controller: red fluorescence corresponds to a disconnected state of the load, and green included.
For reliable operation of the triac at a low temperature (up to 2...4 °C) current the gate electrode is increased to 80 mA, and the pulse duration - up to 0.7 MS (0.3 MS before the moment of the transition voltage through zero and 0.4 MS after). For such momentum and power load 75 watts instantaneous current through the triac on the fronts of the pulse is slightly higher than the normalized value of the current hold. However, in addition to such approval, the load of the regulator must reserve to provide the desired thermal conditions in the repository. At one and the same heat insulation of power change only affects the ratio of time enabled and disabled the loading condition and does not affect adjustable average temperature and electric modes of the elements of the regulator. So the power load during heating (resistors, light bulbs, etc.) it is advisable to increase, so you can use the worst instances triacs with high holding current. For cooling fan power may be small and need a better instance of the triac with a small current. It is important to ensure compliance with this condition. The fact is that if because of the small the load current of the triac in one of the half-cycles will not appear through the load will flow unipolar current, unacceptable for the engine AC.
In the heat stabilizer used details: variable resistor - WP1-64A, thermistor - MMT-1, resistor R9 - KIM power of 0.125 W, the capacitor C2 is K50-29. Switch SА1 - jumper is installed in the desired position before the use of the stabilizer.
Establishing the thermal stabilizer is to install adjustable temperature storage on the thermometer variable resistor R7. In operation the temperature in the warehouse should be monitored periodically to ensure that products are not deteriorated during outages, malfunctions, severe frosts, and so p.
The device has a galvanic connection to the electrical network. It should be remembered in the manufacture and adjustment of stabilizers and precautions: all construction changes be made only in disconnected state.
Author: V. Gulev, Serpukhov, Moscow region.