Refrigerator turn-on delay device. Scheme, description

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Refrigerator turn-on delay device. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Clocks, timers, relays, load switches

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The quality of power supply has not improved over the past years, short-term power outages are a fairly frequent phenomenon, and the task of protecting household appliances from their consequences is still relevant today. I have developed my own version of the refrigerator turn-on delay device, which is more economical and simple compared to the previously published one.

Refrigerator turn-on delay device
Fig. 1

The scheme of the proposed device is shown in fig. 1. It has a transformerless power supply with a ballast capacitor C1 and a rectifier - a diode bridge VD1. When mains voltage is applied to the smoothing capacitor C2, a voltage appears stabilized at 37 V by a circuit of VD2-VD4 zener diodes connected in series. Resistor R1 limits the amplitude of the charging current pulse of capacitor C1 at a safe level.

Since the capacitor C3 is discharged at the moment the mains voltage is turned on, the transistor VT1 is closed, the relay K1 is de-energized, the contacts of the relay K1.1 are open The mains voltage is not supplied to the refrigerator plugged into the XS1 socket.

Capacitor C3 is charged through a high-resistance resistor R3. After 5 ... 6 minutes, the voltage across the capacitor reaches 3 ... 5 V - the threshold voltage of the transistor VT1. When the transistor opens, relay K1 is activated and contacts K1.1 supplies the voltage to the triac control electrode through the current-limiting resistor R4 to open the triac - the refrigerator is connected to the network. The charging of the capacitor C3 stops when the voltage reaches 6,5 ... 7 V, which is safe for the transistor VT1. It is limited at this level by the Zener diode VD4.

Refrigerator turn-on delay device
Fig. 2

With a short-term power failure in the network, the capacitor C3 quickly discharges through the diode VD5 and the relatively low-resistance resistor R2. During the discharge of this capacitor to the threshold voltage of the transistor VT1, the capacitor C2 has time to discharge through the winding of the relay K1 and the still open transistor VT1. In this case, the contacts of relay K1.1 open, the device returns to its original state.

Establishing the device is reduced to the selection of the resistor R3 to obtain the necessary delay in turning on the refrigerator.

As C1, a capacitor was used from the mains filter of a switching power supply of an imported device. It can be replaced by two K73-17 capacitors connected in series with a capacity of 0,33 microfarads for a voltage of at least 400 V. Oxide capacitors - K50-35 or imported. Resistors - any power indicated on the diagram. Relay K1 - RES10 version RS4.529.031-02 with a winding resistance of 4,5 kOhm and a trip current of 8 mA.

The voltage class of the triac TS 106-10 (the last digit in its designation) must be at least 4, which means a permissible voltage of 400 V. The triac must be fixed on a heat sink - a metal plate with an area of several square centimeters.

Diodes KD522A are replaced by any low-power silicon ones. Two KS515A zener diodes can be replaced by a circuit of any number of medium-power zener diodes connected in series with a total stabilization voltage of 30 ... 32 V. Instead of a KS168A zener diode, another one with a stabilization voltage of 6 ... 9 V is also suitable. individual diodes with a permissible reverse voltage of at least 107 V, for example, KD400G or 105 N1.

The design of the device can be very different. For example, using small-sized imported zener diodes, I fit it into the body of a conventional XS1 power outlet. This design with the cover removed is shown in Fig. 2. The printed circuit board was not developed.

The refrigerator in most cases is installed in the kitchen, and this is a room with high humidity. To protect the elements of the timing chain from it and to increase the stability of the generated delay, it is recommended to cover the installation of the device with several layers of NTs-222 varnish or epoxy glue diluted with acetone.

Author: K. Moroz

See other articles Section Clocks, timers, relays, load switches.

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