When you leave, turn off the light. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Lighting

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Every time we leave for work in the morning, we try not to forget to turn off the lights and electrical appliances in the apartment. Meanwhile, this function can be successfully performed by an automaton consisting of three main blocks (Fig. 1): sensors, a digital control device, and a key. Here's how it works.

Rice. 1. Functional diagram of the automatic device: 1 - sensors, 2 - digital control device, 3 - key

The light from the lamp H1 illuminates the photodiodes B1 to B2 (Fig. 2), as a result of which the transistors V1 and V2 are open and a low potential "1.1" is supplied to the inputs of the inverters D1.2, D0, which is then converted to a high "1" on exit. There are four possible combinations of the state of the photodiodes when crossing the light flux: 1) B1, B2 - open, 2) B1 - closed, B2 - open, 3) B1, B2 - closed, 4) B1 - open, B2 - closed. Thus, for each entering the apartment, the sequence of combinations will be 1, 2, 3, 4, 1, and for the exiting - 1, 4, 3, 2, 1. Now you need to "catch" these two sequences of combinations, convert sludge into single impulses and apply, respectively, to the summing or subtracting input of the reversible counter D6.

Rice. 2. Schematic diagram of the machine "When leaving, turn off the light!" (click to enlarge)

This task is performed by a digital control device assembled on logic elements (chips D1-D7). It works as follows. Suppose a person entered the apartment. Combination 1, which is the original one, is perceived by the logical element ZI-NOT (D5.3), at the output of which the potential "0" appears, setting the outputs of the RS-trnger assembled on logical elements 2I-NOT (D3.2, D3.3, D4.1 .4.2, DXNUMX) to the zero state.

Combination 2 is perceived by the 2I-NOT logic element (D3.1), at the output of which a zero potential appears, which sets the RS flip-flop assembled on the 2I-NOT logic elements (D3.2, D3.3) to the state "1". Combination 3 is skipped.

Combination 4 is perceived by the logic element 3I-NOT (D5.2), as a result of which the potential "1" is supplied to the counting input "+6" of the reversible counter D0, which increases the contents of the counter by 1. But combination 4 is also perceived by the logic element 2I- NOT (D2.4), the output of which appears "0", setting the RS flip-flop (D4,1, D4.2) to the state "1".

Combination 1 is again perceived by the logical element 3I-NOT (D5.3), the zero potential from the output of which returns the entire device to its original state.

Thus, the device only works when the person has completely entered the apartment. In this case, the contents of the reversible counter D6 increases by one (another person entered the apartment).

It is easy to see that when a person leaves the apartment, the contents of the reverse counter decreases by 1.

If the last person left the apartment, then the number 7, written in binary code (0111), will be perceived by the logical element 4I-NOT (D7.1), and the potential "0", having entered the key assembled on transistor V3, will close his. In this case, the transistor key V5 will open, relay K1 (MKU48-S, passport RA4.500.197P) will work, contacts K1.1, K1.2 will open, and the flow of electricity to the apartment will stop.

KT315G transistors can be replaced with any other KT312, KT315, KT301 series, and KT608B - with KT604, KT605, KT606 with any letter index.

Instead of MKU48-S, you can use a relay of another type with a response voltage of 24 V, the contact system of which allows you to switch alternating current with a voltage of 220 V and a power of 2-5A.

Photodiode FD-6G can be replaced by FD-3.

The power supply circuit is shown in Figure 3.

Rice. 3. Schematic diagram of the power supply (click to enlarge)

The 5 V voltage regulator is assembled on a D8 chip and a V14 transistor.

Transformer T1 is made on the magnetic circuit Ш16X32, Windings I and II contain, respectively, 1200 and 1600 turns of PEV-1 0,15 wire, winding III - 360 turns of PEV-1 0,2, IV - 120 turns of PEV-1 0,45.

The details of the device (except for relay K1, power supply and button S1) are mounted on a circuit board (Fig. 4) 95X75 mm in size, made of double-sided foil fiberglass 1,5 mm thick. It is housed in any suitable plastic or metal case.

Rice. 4. Digital control circuit board with parts diagram (M1:1).

Set up the device as follows. After checking the correct installation, disconnect the inputs of the digital control circuit from the outputs of the inverters (D1.1, D1.2) and connect two keys assembled on the K155LAZ chip (Fig. 5). With their help, the intersection of the light flux is imitated. Then check the correct passage of the signal.

Fig. 5

The key is on the K155LA3 chip. The machine is installed inside the apartment next to the front door so that the photodiodes are at a height of 65-70 cm from the floor. At the same level, but on the opposite wall, there is an H1 lamp with a reflector from a flashlight. A voltage of 5 V is supplied to it from the power supply.

The reliability of the operation of an automatic device depends on the stability and power of the light flux incident on the photodiodes. Therefore, the reflector lamp and sensors must be rigidly fixed.

The reliability can be increased by installing additional converging lenses in front of the photodiodes (Fig. 6).

Rice. 6. Installation of additional lenses: 1 - lenses, 2 - housing cover, 3 - circuit board

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