corridor switch. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Lighting. Control schemes

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In the wiring for lighting long corridors, flights of stairs, porches, long hangars and in other places where it is necessary to turn on and off the light from two (entrance and exit, beginning and end of the corridor) or more places, so-called corridor switches are usually used. Install them at different ends of the corridor. The circuit is known to any electrician, and to change the state of lighting (on, off), the switch must be switched to the opposite of the former position. Such a scheme requires laying three wires to the switches instead of two, and this is only if you need to control the lighting from two places. If there should be more control points - three, four, then not only the wiring becomes more complicated in the geometric profession, but the control process itself becomes more complicated, since it is already necessary to choose not from two, but from three, four positions of the switch knob.

In this case, a good way out can be an electronic switch based on a D-flip-flop, the state of which can be changed with a momentary button. Moreover, the number of buttons is completely unlimited. Buttons are connected in parallel to one low-power two-wire line, in any place and in any quantity. Pressing any of these buttons changes the state of the lighting (on, off).

Figure 1 shows a diagram of the first version of the corridor switch - with one lamp.

Fig. 1

The voltage from the network is supplied to the circuit. When you turn on the power (for example, turn on the switch in the shield), the IC D1 receives a supply voltage of 12 V. This voltage is generated using the simplest transformerless DC source. The voltage from the mains is rectified by the diode VD4 and one of the diodes of the rectifier bridge VD5 ... VD8. Resistor R5 with a zener diode VD1 forms a parametric stabilizer that lowers and stabilizes the voltage at 12 V. Capacitor C3 smoothes out ripples. When power is applied, charging C1 through R2 creates a pulse that sets the trigger to zero. The voltage supplied to the VT1 gate is zero, the transistor itself is closed and the H1 lamp is off.

To turn on the lamp, you need to change the state of the D-trigger to the opposite. To do this, press and release the S1 button (or any of the S1-SN). So we create at the entrance. C is a pulse that sets the flip-flop to the state that is at its input D. Since D is connected to the inverted output, the level on it is opposite to that supplied to the gate of the field-effect transistor. As a result, the level at the direct output of D1 changes with each press of the button. When the unit of the transistor VT1 opens at the direct output D1 and turns on the lamp.

The trigger on the chip works very quickly, and any button rattles at least a little. Therefore, when the button is pressed, the trigger can be set to any random position, since one press gives not only one main impulse, but also a lot of short impulses from a bounce. So, in order to suppress failures from chatter, the C2-R3 chain was introduced. It prevents the state at input D of the flip-flop from changing too quickly. Therefore, no matter how many parasitic pulses a rattling button generates, if they are shorter than the time constant of this circuit, there will be only one state change. Resistor R4 unloads the trigger output from the influence of the charging current of the gate capacitance of a powerful field-effect transistor. Diodes VD2 and VD3 accelerate the discharge of the gate capacitance and suppress voltage surges that may be on the gate capacitance.

The circuit in Figure 1 controls only one lamp (or one lighting circuit consisting of several lamps). This is not always convenient, in cases with a very long room, it is desirable to make two groups of lamps that could be controlled from anywhere in the room, respectively, by setting the buttons at these points

Figure 2 shows a corridor switch operating with two lamps (or two lighting circuits consisting of several lamps). Here, the second trigger of the K561TM2 chip is used, which is not involved in the first circuit. It is switched on sequentially to the first trigger, forming a two-digit binary counter, which differs from the "typical" one only in the presence of the R3-C2 delay circuit in the first trigger link. Now the state of the trigger outputs will change according to the binary code.

Fig. 2

When the power is turned on, both flip-flops are set to the zero state, so that this happens, the input R of the second flip-flop is connected to the same input of the first. Now the C1-R2 circuit acts on both flip-flops, resetting them when power is applied.

With the first press of the button, the trigger D1.1 is set to a single state - the H1 lamp turns on. If you press the button again, the state of the trigger D1.1 will change and the lamp H1 will go out, but at the same time the state of the second trigger D1.2 will change - a logical unit will be set at its direct output and the transistor VT2 will open, which will turn on the lamp H2.

With the third press of the button, the binary counter will go to the "3" state, the ones will be on the direct outputs of both triggers and both lamps will be on. And with the fourth press, both lamps will go out.

There are no other differences in the scheme.

Using IRF840 transistors and 1N4007 diodes in the rectifier bridges, the power of each lamp or each lighting circuit, if it consists of several lamps, should not exceed 200 watts. If the loads are more powerful, this will require replacing the 1N4007 diodes in the bridges with diodes corresponding to the power load. Plus, field effect transistors will need to be put on radiators. In general, IRF840 in this circuit can control loads up to 2000 W, but only with radiators, and at load power up to 200W, due to low resistance in the open state, the power drops on the transistors themselves are very insignificant, therefore, radiators when working with loads up to 200 W im not required.

Diodes 1N4148 can be replaced with almost any diode, for example, KD521, KD522 KD102, KD103.

Diodes 1N4007 can be replaced by any rectifier diodes, for a voltage of at least 400 V and for current, respectively, the load power. For example, with a load of not more than 120 watts, KD209 diodes can be used.

The D814D zener diode can be replaced with any 11 ... 13 V zener diode. It is advisable to use a medium power zener diode or in a metal case. In general, you need to take into account that when the zener diode breaks, 220 V will go to the entire circuit (microcircuit, transistor gates), which will almost completely destroy it, so the reliability of the zener diode is of great importance.

Author: Sankov E.M.

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