DIY light switch off timer. Do-it-yourself light switch on and off timer

A time relay is installed in many models of equipment and household appliances. This device allows you to automatically turn on or off the equipment and not waste time controlling certain actions. Craftsmen often design various devices for their own needs. For many designs, it is necessary to make a time relay with your own hands, since branded devices are not always suitable in a particular situation. However, before starting to make a homemade timer, novice craftsmen are advised to familiarize themselves with the main types of such relays and the principles of their operation.

How does an electronic timer work?

Unlike the very first timers with a clock mechanism, modern time relays operate much faster and more efficiently. Many of them are based on microcontrollers (MCUs) capable of performing millions of operations per second.

This speed is not needed to turn it on and off, so the microcontrollers were connected to timers capable of counting pulses occurring inside the MK. Thus, the central processor executes its main program, and the timer ensures timely actions at certain intervals. An understanding of the operating principle of these devices will be needed even when making a simple capacitive time relay with your own hands.

Operating principle of a time relay:

• After the start command, the timer starts counting from zero.
• Under the influence of each pulse, the contents of the counter increase by one and gradually acquire a maximum value.
• Next, the contents of the counter are reset to zero, since it becomes “overflowing”. At this moment the time delay ends.

This simple design allows for a maximum shutter speed of 255 microseconds. However, most devices require seconds, minutes and even hours, which raises the question of how to create the required time intervals.

The way out of this situation is quite simple. When the timer overflows, this event causes the main program to be interrupted. Next, the processor transitions to the corresponding subroutine, which consists of small delays for any period of time that is currently required. This subroutine that serves the interrupt is very short, consisting of no more than a few dozen commands. At the end of its action, all functions return to the main program, which continues to work from the same place.

The usual repetition of commands does not occur mechanically, but under the guidance of a special command that reserves memory and creates short time delays.

Main types of time relays

When constructing a homemade time relay, a specific model is taken as a sample. Therefore, every master should imagine the basic devices that perform the functions of timers. The main task of any time relay is to obtain a delay between the input and output signal. Various methods are used to create this delay.

Electromechanical relays include pneumatic devices. Their design includes an electromagnetic drive and a pneumatic attachment. The device coil is designed for alternating current with an operating voltage from 12 to 660 V - a total of 16 exact ratings are set. The operating frequency is 50-60 Hz. With these parameters, you can make a 12V time relay with your own hands. Depending on the design, the shutter speed of such relays begins when the electromagnetic drive is triggered or released.

The time is set using a screw that regulates the cross-section of the hole through which air exits the chamber. The parameters of these devices are not stable, so time relays are more widely used.

These devices use a specialized microcircuit KR512PS10. Voltage is applied to it through a rectifier bridge and a stabilizer, after which the internal generator of the microcircuit begins generating pulses. To adjust their frequency, a variable resistor is used, located on the front panel of the device and connected in series with a capacitor that sets the time. The received pulses are counted by a counter having a variable division coefficient. These designs can be taken as a basis to make a cyclic time relay and other similar devices.

Modern time relays are made on the basis of microcontrollers and are unlikely to be suitable for home craftsmen as a sample. If it is necessary to obtain precise time intervals, it is recommended to use a ready-made product.

DIY time relay 220V circuit

Quite often, for designs made by home craftsmen, it is necessary to make a simple time relay with your own hands. Reliable and inexpensive timers fully justify themselves during operation.

The basis of most home-made devices is the same KR512PS10 microcircuit, which is powered through a parametric stabilizer with a stabilization voltage of approximately 5 V. When the power is turned on, a chain consisting of a resistor and a capacitor forms a reset pulse for the microcircuit. At the same time, the internal generator is started, the frequency of which is set by a chain of another resistor and capacitor. After this, the internal counter of the microcircuit begins counting pulses.

The number of pulses is also the counter division factor. This parameter is set by switching the pins of the microcircuit. When the output reaches a high level, the counter stops. At the other output, the pulses also reach a high level, causing VT1 to open. Through it, relay K1 is switched on, the contacts of which directly control the load. This circuit is ideal for solving the problem of how to make a 220V time relay with your own hands. To restart the time delay, it is quite enough to turn off the relay for a short time and then turn it on again.

In everyday life, it is often necessary to turn off the lights after a certain time. There is a need for storage rooms and simple outbuildings. In turn, and in other cases when it is necessary to limit the operation of any electronic device in time, a simple digital timer will be used in place, which allows you to turn on or off the load after a certain period.

Simple digital light on/off timer, which you can assemble with your own hands, is built on only one integrated counter K561IE16. As you know, to operate any counter you need an external clock generator. In our case, its role is played by a simple flashing LED.

Description of the operation circuit of a simple digital timer

As soon as the timer power is turned on, C1 is charged through resistance R2, as a result of which logic 1 briefly appears at pin 11, turning all counter outputs to zero. The transistor connected to the meter output will open and the relay will operate, connecting the load with its contacts.

From a flashing LED with a frequency of about 1.4 Hz, pulses are sent to the clock input (pin 10) of the counter DD1. With each fall of the input pulse, the counter increments. After 256 pulses have passed (in time this will take approximately 256 / 1.4 Hz = 183 seconds or ~ 3 minutes), logic 1 appears at pin 12. In this regard, the transistor will close, de-energizing the load. Plus, logic 1 from output 12 is supplied to the clock input DD1 through the diode VD1, thereby stopping the timer.

The frequency of operation of the timer can be selected by connecting the connection point of resistor R3 and diode VD1 to various outputs of DD1. By slightly adjusting this circuit, it is possible to build a timer that performs the opposite function. The change affects transistor VT1. It must be replaced with a transistor of a different structure.

Now, when log.1 appears at the output of the counter, the transistor will open and turn on the load. Instead of an electric relay in this version, it is possible to turn on a simple sound emitter with an internal generator, for example, HCM1612X. The electric emitter must be connected with correct polarity.

Light On/Off Timer Details

Diodes VD1-VD2 series KD103, KD522, KD103, KD521, KD102. KT814A transistors can be replaced with KT973 or KT814. arbitrary from the KT604, KT815 series. In addition to the K561IE16 counter, it is possible to use its foreign analog CD4020B. You can also use the CD4060 chip, which already has a clock generator, so the LED and resistance R1 can be removed. LED – flashing type ARL5013URCB, L816BRSCВ, L56DGD,

The timer is quite economical in terms of energy consumption. The current consumed by the timer, not including the relay current, is about 11 mA.

Content:

Mechanical time relays have been used for a long time; the simplest example is an hourglass, when a certain volume of sand is poured from the upper part to the lower part at measured intervals. After this, a mechanical device is set in motion under the weight of the sand. A cuckoo clock is also a simple mechanical time relay, where a weight on a chain sets a gear mechanism in motion, and at certain intervals the cuckoo moves out.

In old washing machines, a mechanical timer started, after a set time it closed the contacts, turning on the electric motor. With the advent of electricity, mechanical devices were replaced by electronic time relays; modern watches with timer mode are made entirely of electronic elements. But the tasks remain the same: turning on and off certain electronic devices, electric motors that drive mechanical devices. Sometimes in complex conveyor processes this device is called a delay relay. Today, with the availability of electronic parts, the question “How to make a time relay?” does not cause any difficulties.

Classification of timers and design features

All timers can be divided by design:

• a simple timer of a mechanical device, an example would be the timer of an old-style washing machine RVTs-6-50;

• timers with electronic elements for connecting the load to the network - such an element can be a thyristor, a time relay itself on transistors or microcircuits. The role of the turn-on delay element is performed by an electrolytic capacitor;

• with pneumatic drives for turning devices on and off.

By installation method:

• Manufacturers of household appliances and special equipment install timers in the case, control buttons are displayed on the front panel;
• a homemade time relay can be placed anywhere depending on the needs and fantasies of the manufacturer. Previously, car enthusiasts installed a 12 V power supply time relay to turn on the heating of the oil in the sump. 12 V in this case is a very convenient on-board power supply for the car from the battery: no additional power source is required, low energy consumption, the battery will not be discharged.

Therefore, the dimensions and mountings comply with these standards.

By connection method:

• the location of the connection elements can be front, rear or side;
• power and control wires are removed from the housing and connected by soldering or bolted connections in switchgear;
• Connectors for connection are installed on the case.

For controls and programming:

• packet switch;
• potentiometer;
• buttons.

Manufacturers use all these design features of time relays taking into account the conditions for the location of timers and their functional purpose; homemade products can combine a combination of all options in one product.

Advantages and disadvantages of different types of timers

Statistics show that time relays with electronic elements for switching on and off the load are most in demand. This is due to a number of advantages:

• compact dimensions;
• low energy costs;
• wide range of power supply choices, there are 12 V DC or 220 V AC models;
• lack of mechanical drives;
• large selection of programming options;
• long service life, the electronic timer does not limit the number of operations, like mechanical devices;
• Easily dismantled and connected to other equipment.

The circuits of these devices are not complicated; those who have basic knowledge in the field of electronics and practical soldering skills can make a time relay with their own hands.

DIY time relay

Let's look at one of the simple ways to make a time relay at home with your own hands; transistor models are the most affordable. You don't need a lot of details for this:

When the toggle switch S1 is turned on, the capacitor C1 is charged to a supply voltage level of 9–12 V through the variable resistor R1 and R3, the switch of the transistor VT1 opens. After charging the capacitor, the transistor closes and de-energizes the relay; depending on the design of the group of contacts, the load is turned off or connected.

The charging time is adjusted by resistor R1, experimentally; on the body of a home-made timer, you can apply a graduation in minutes until the moment of operation. Turning off toggle switch S1 leads to complete discharge of the capacitor through resistor R2, the operation process is cyclic, after discharge the timer is returned to its original state.

A homemade timer has a simple circuit, very unpretentious, the values ​​of the elements are not critical, after proper assembly it does not require debugging, it works immediately, so it is not difficult to assemble it yourself. As a power source, you can use 9 V batteries, 12 V batteries or 220 V mains power through a voltage converter to 12 V DC.

Often time relays are made using a relay powered by a 12 V electromagnet, like that of the manufacturer FUJITSU-TAKAMISAWA (Japan). This is very convenient, the load contacts can withstand 220 V / 2 A.

The main component of the technical equipment of a modern home can be made DIY time relay. The essence of such a controller is to open and close an electrical circuit according to specified parameters in order to control the presence of voltage, for example, in a lighting network.

Purpose and design features

The most advanced such device is timer consisting of electronic elements. Its moment of operation is controlled by an electronic circuit according to specified parameters, and the release time of the relay itself is calculated in seconds, minutes, hours or days.

According to the general classifier, timers to turn off or turn on an electrical circuit are divided into the following types:

• Mechanical device.
• Timer with an electronic load switch, for example, built on a thyristor.
• The operating principle of the device is based on a pneumatic drive to turn it off and on.

Structurally, the response timer can be manufactured for installation on a flat plane, with a lock on a DIN rail, and for mounting on the front panel of an automation and indication board.

Also, according to the connection method, such a device can be front, rear, side, or plugged in through a special detachable element. Time programming can be done using a switch, potentiometer or pushbuttons.

As already noted, of all the listed types of triggering devices for a given time, the greatest demand is for a time relay circuit with electronic shutdown element.

This is explained by the fact that such a timer, operating on voltage, for example, 12v, has the following technical features:

• compact dimensions;
• minimal energy costs;
• absence of moving mechanisms with the exception of switching and switching contacts;
• widely programmable task;
• long service life, independent of operation cycles.

The most interesting thing is that you can easily make a timer yourself at home. In practice, there are many types of circuits that provide a comprehensive answer to the question of how to make a time relay.

The simplest 12V timer at home

The simplest solution is time relay 12 volt. Such a relay can be powered from a standard 12v power supply, of which there are many sold in various stores.

The figure below shows a diagram of a device for turning on and automatically turning off a lighting network, assembled on one integrated counter of the K561IE16 type.

Drawing. A variant of a 12v relay circuit that turns on the load for 3 minutes when power is applied.

This circuit is interesting in that it acts as a clock pulse generator flashing LED VD1. Its flickering frequency is 1.4 Hz. If you can’t find an LED of this particular brand, you can use a similar one.

Let's consider the initial state of operation, at the moment of supplying 12v power. At the initial moment of time, capacitor C1 is fully charged through resistor R2. Log.1 appears at pin No. 11, making this element zeroed.

Transistor connected to output integral counter, opens and supplies 12V voltage to the relay coil, through the power contacts of which the load switching circuit is closed.

The further principle of operation of the circuit operating at a voltage of 12V is as follows: pulse reading, coming from the VD1 indicator with a frequency of 1.4 Hz to contact No. 10 of the DD1 counter. With each decrease in the level of the incoming signal, there is, so to speak, an increment in the value of the counting element.

On admission 256 pulses(this equals 183 seconds or 3 minutes) a log appears on pin No. 12. 1. This signal is a command to close transistor VT1 and interrupt the load connection circuit through the relay contact system.

At the same time, logic 1 from pin No. 12 is supplied through diode VD2 to clock leg C of element DD1. This signal blocks the possibility of receiving clock pulses in the future; the timer will no longer operate, until the 12V power supply is reset.

The initial parameters for the operation timer are set in different ways by connecting the transistor VT1 and the diode VD3 indicated in the diagram.

By slightly transforming such a device, you can make a circuit that has reverse operating principle. The KT814A transistor should be changed to another type - KT815A, the emitter should be connected to the common wire, the collector to the first contact of the relay. The second contact of the relay should be connected to a 12V supply voltage.

Drawing. A variant of a 12v relay circuit that turns on the load 3 minutes after power is applied.

Now after power on relay will be turned off, and the control pulse that opens the relay in the form of log.1 output 12 of element DD1 will open the transistor and supply a voltage of 12V to the coil. After which, the load will be connected to the electrical network through the power contacts.

This version of the timer, operating from a voltage of 12V, will keep the load disconnected for a period of 3 minutes, and then connect it.

When making the circuit, do not forget to place a capacitor with a capacity of 0.1 μF, designated C3 in the circuit and with a voltage of 50V, as close as possible to the supply terminals of the microcircuit, otherwise the meter will often fail and holding time the relay will sometimes be smaller than it should be.

An interesting feature of the operating principle of this scheme is the presence of additional capabilities, which, if possible, are easy to implement.

In particular, this is programming the exposure time. By using, for example, a DIP switch as shown in the figure, you can connect some contacts of the switches to the outputs of the counter DD1, and combine the second contacts together and connect them to the connection point of the elements VD2 and R3.

Thus, with the help of microswitches you can program holding time relay.

Connecting the connection point of elements VD2 and R3 to different outputs of DD1 will change the dwell time as follows:

Complete set of circuit elements

To make such a timer operating at 12v voltage, you need to correctly prepare the circuit parts.

The elements of the scheme are:

• diodes VD1 - VD2, marked 1N4128, KD103, KD102, KD522.
• The transistor that supplies 12v voltage to the relay is designated KT814A or KT814.
• Integral counter, the basis of the operating principle of the circuit, marked K561IE16 or CD4060.
• LED device ARL5013URCB or L816BRSCB series.

It is important to remember here that when making a homemade device, you must use the elements indicated in the diagram and follow safety rules.

A simple scheme for beginners

Beginner radio amateurs can try to make a timer, the principle of operation of which is as simple as possible.

However, with such a simple device you can turn on the load for a specific time. True, the time for which the load is connected is always the same.

The operating algorithm of the circuit is as follows. When the button labeled SF1 is closed, capacitor C1 is fully charged. When it is released, the specified element C1 begins to discharge through resistance R1 and the base of the transistor, designated VT1 in the circuit.

For the duration of the discharge current of capacitor C1, until it is sufficient to maintain transistor VT1 in the open state, relay K1 will be on and then off.

The indicated ratings on the circuit elements ensure that the load operates for 5 minutes. The operating principle of the device is such that the dwell time depends on the capacitance of capacitor C1, resistance R1, current transfer coefficient of transistor VT1 and the operating current of relay K1.

If desired, you can change the response time by changing the capacitance C1.

Video on the topic

Designed to turn on the load for a specified time interval. The range of possible timer intervals is from 1 second to 24 hours.

The timer is very simple, does not contain scarce parts and can be repeated by an averagely qualified radio amateur. In some ways, this timer is an improved version of the previously published one. The device can find practical application, for example, in the manufacture of printed circuit boards using photoresist to limit the time the ultraviolet lamp is turned on when the photoresist surface is exposed.

The design has a galvanic connection with a 220 volt household network, so special care should be taken during the manufacturing and testing process. Once placed in the housing, the timer is no longer dangerous.

The timer can be assembled according to one of two circuit options:

or

For the first circuit, the recommended power of the switched load is no more than 100 watts, since the triac KU208G It is placed in a case without a radiator and will get very hot under higher loads.

If you need to switch a load with high power, it is recommended to install a triac on the radiator, or try using another, more powerful one.

In the second version of the circuit, a relay is used instead of a triac to switch the load, so the load power is limited only by the switching ability of the relay contacts.

In the finished assembled version of the device, the control button and other parts of the circuit must be well isolated from contact with the user's hand.

Microcontroller supply voltage 5 volts, stabilized by microcircuit 78L05.

Structurally, the entire device fit into the housing from the adapter, in which the transformer burned out, but the housing was preserved.

The circuit is assembled on a small circuit board; no printed circuit board was developed. The parts used are not in short supply and widely available, both domestic and imported. In the first circuit with a triac, you can use a reed relay RGK15 with switching voltage 5 volts, triac VS1– KU208G, can be used KU208V or foreign analogues with similar characteristics.

In the second circuit as a relay K1 an imported relay was used with one group of normally open contacts rated for a current of 10 A, the name of the relay SDT-SS-112DM. I believe that it can be replaced with a different type of relay with a winding resistance of approximately 300 ohms, with a voltage of 12 V, and the relay contacts should be designed for the maximum current of the intended load. Transistor VT1, a switching relay, suitable for any average power of npn conductivity, for example, domestic ones can be recommended KT315 or KT503. Microcontroller – AVR family ATtiny13.

Diodes VD1,VD2 can be replaced by domestic ones, for example D226B or KD105 with a reverse voltage of at least 350-400V, zener diode ZD1- any low-power one with a stabilization voltage of 12-20 volts. Any electrodynamic emitter without a built-in generator with a winding resistance of 30-50 Ohms is suitable as a buzzer.

In the project, the clock frequency of the microcontroller's internal oscillator is chosen to be 1.2 MHz (9.6/8). How to set fuses for two popular programmers ( Chip Blaster And PonyProg) when programming the chip is shown in the pictures below.

How to program the timer time

By holding down the SB1 button for a long time, go to the timer time setting mode (details below) and enter the required number of time intervals. This is done once, all subsequent work cycles will adhere to these settings until you need to change them to others in the same way.

Timer time setting sequence

Turn on the power, indicator HL1 Does not burn. Press the button " SET" and hold it pressed for a long time until the LED HL1 will begin to blink at a frequency of 1 time per second (1 blink = 1 discrete interval).

The sequence of setting the timer time goes in the following sequence: first there is a set of seconds, then a set of minutes follows, then a set of hours, and then exits the timer time setting mode.

Observing the blinking of the LED, we count the number of flashes (each is accompanied by the sound of a buzzer). After counting down the required number of seconds, release the button. After this, the number of dialed seconds is stored in memory, and the HL1 indicator begins to flash rapidly, which means that the minutes have begun to be entered.

Press and hold the " button again SET" - Light-emitting diode HL1 blinks at a frequency of 1 time per second. Again, count down the required number of minutes using flashes or sound signals, and release the button. After this the indicator HL1 lights up constantly - this means that you can now enter the hours.

Entering the clock is carried out in exactly the same way - press and hold the button, count the required number of signals, release the button.

Upon completion of the installation procedure, you must wait for the buzzer to sound, indicating the end of the time setting process. After this, the device goes into the initial standby state and is ready for use.

If the time interval involves setting a small interval, for example a few seconds, then, having entered the required number of seconds, you need to release the button and do not press the button again, waiting for the buzzer to sound the end of setting the time. In this case, only the dialed number of seconds is stored in memory, and the minutes and hours are reset to zero.

We do the same thing if we DO NOT need to enter hourly intervals: having set seconds and minutes, release the button and wait for a signal to memorize the time.

The timer is now ready to use.

The timer is started by briefly pressing the button " SET"(aka "Start"). After pressing the button, the buzzer will beep to notify you of the beginning of the cycle, the load will turn on for the time set by the timer. If the timer delay exceeds 1 minute, then the indicator HL1 will flash every 10 seconds. At the end of the cycle, the load will turn off and the beep will sound again for about 5 seconds. After this, the device will go into the initial standby state.

If you need to interrupt the timer operation without waiting for the specified working interval to expire, you can do it in two ways:

1. if you do not intend to change the timer time, you just need to unplug the plug from the socket - the load will turn off;