Time relay: how to make a 12 volt device with your own hands according to the diagrams

With a device such as a 12 volt time relay, you can save a lot of money on your electricity bills. This is due to the automatic shutdown of the light bulb, for example, after a certain period of time. This is very convenient, since the light will not just turn on if you forget to turn it off. In addition, such a device is quite simple to make with your own hands, even without special skills in electrical installation.

Scope of application

In the process of the development of human civilization, people have always tried to make life easier for themselves and came up with various useful devices. After the popularization of electrical equipment among the population, it became necessary to invent a timer that would turn off the device after a certain time. That is, you can turn on the unit and go about your business, after which the timer will automatically turn it off at the specified or programmed time. For these purposes, a time relay was created. The 12 V device is characterized by ease of manufacture, so it will not be difficult to make it yourself.

An example is relays from an old washing machine that were popular during the Soviet Union. In the classic design, they had a mechanical round knob with graduations. After scrolling it in a certain direction, the countdown began, and the machine stopped when the timer inside the relay reached the value "zero".

The time relay also exists in modern electrical engineering:

• microwave ovens or other similar equipment;
• automatic irrigation systems;
• fans for air injection or for exhaust;
• automatic lighting control systems.

As a rule, the device is made on the basis of a microcontroller. It not only performs the function of a time relay, but also regulates all automatic processes in the device, that is, it is the main control unit.

This is easier and more economical for the manufacturer, since there is no need to install two elements that perform the same function, if all tasks can be provided by one control unit.

All models (both factory and home-made), according to the type of element located at the outlet, are divided into:

• relay;
• triac;
• thyristor.

In the first variant, the entire load is connected and passed through the "dry contact". It is the most reliable among analogs. For self-production, you can also use a microcontroller. But it is impractical to do this, since ordinary home-made time relays are made for simple tasks. Therefore, using microcontrollers is a waste of money. It is better in this case to use simple circuits on capacitors and transistors.

DIY making

The principle of operation of the time relay is the start of the set delay. First, the timer starts with the set time, and then the countdown begins. The device to which the timer was connected starts working - light or electric motor turns on. At the moment when the time is up, the relay cuts off the current supply and disconnects the device from the power supply.

The easiest transistor option

Time relay circuits using transistors are considered the simplest. The simplest model has only 8 components. You don't even need to use a board to make it, and all the parts can be soldered together. Such a device is often made in order to connect lighting through it. After pressing the button, the light turns on, and after a few minutes it turns off.

For manufacturing, you will need the following components:

• several resistors;
• button for mechanical start of the device;
• relay for power regulation;
• transistor type KT937A;
• several capacitors;
• rectifier diodes;
• variable resistor (to adjust the time).

The above-described delay process, due to which the device operates, occurs due to the charging of the capacitor to the degree of power supply of the transistor switch. One of the main tasks in the manufacture of such a structure is the correct selection of resistance. It must be exactly at the level that the relay closes after the signal is applied. In this case, only after the signal is sent from another element, the load can be fed back. The selection is carried out through experiments.

This type of transistor has a small supply current. If you choose a large resistance winding, then the operating range can be safely increased to several hours. It is also worth noting that the device begins to work only at the last stage, when the work comes to an end, and until that time it practically does not use electricity.

If the device is connected to a regular battery, then it will function for a long time. Thus, making a 12 volt time relay with your own hands is not a difficult task.

Using microcircuits

There are significant disadvantages in microcircuits based on transistors. It is very difficult to calculate the delay time; therefore, it is necessary to discharge the capacitor before each turn on. The use of microcircuits eliminates these disadvantages, but the operation of the device itself becomes more complicated. Nevertheless, even with the initial skills in working with electrical equipment, it is possible to make a time relay of this type without much difficulty.

A device based on microcircuits will work much better than a device based on transistors: there will be much fewer unforeseen operations. This is due to increased control over currents, they act more rigidly. The transistor will operate in one and the opposite direction only when needed.

There are also more complex circuits based on microcontrollers. But in order to assemble them yourself, you need to have some experience, since various difficulties may arise in working with both programming and soldering.

Power supply 220 volts

All circuits previously described are designed to operate on 12 volts. In order to connect 220 volts, it is necessary to install a magnetic starter at the output of the circuit. This must be done without fail when installed in a device with an electric motor or other consumers that require a high load.

But on the other hand, an elementary thyristor-based device can be assembled to control lighting. It should be noted that it is not recommended to turn on other devices through such a device.

As components you may need:

• switch;
• capacitors;
• 4 diodes;
• thyristor.

Such a device works according to the general principle, like all circuits of this type. The capacitors in it are charged gradually. The delay is regulated by a special switch, and the range of action is selected by the capacitance of the capacitors. Any contact with structural parts can result in an electric shock, this should be remembered.