Schemes of simple electronic time relays. How to make your own timer from an electronic clock
Timer circuit
The circuit works as follows: when you press the button, capacitor C1 is charged through resistor R3. When the capacitor is charged, transistor VT1 opens. It amplifies transistor VT2, through which the load current will flow. But capacitor C1 is discharged through resistors R1 and R2. The lower the value of resistor R1, the faster the capacitor will discharge. Resistor R2 is installed so that after charging the capacitor, the capacitor does not discharge instantly. Thus, we increase the life of the capacitor.
I decided to assemble the circuit on a one-sided PCB 25mm long and 20mm wide. I drew the paths on the board with a permanent marker and painted over the top with paint. I etched it in ferric chloride for about forty minutes. I washed off the paint with a solvent and then tinned the board.
Now let's start soldering. First of all, we solder the transistors, since they have short legs, and therefore it is more difficult to solder. Then we solder the capacitor. Then all the resistors, followed by the LED, after the wires and the terminal block. If everything is soldered correctly, the circuit will work immediately.
Transistors can be replaced with any n-p-n structures. If you connect a load whose current is higher than 50mA, then I advise you to replace the KT315 transistor with a more powerful one. Resistor R3 can be replaced with any other one with a resistance of 200-1000 Ohms.
Resistor R2 can be replaced with any other one with a resistance of 50-1000 Ohms. Resistor R1 can be replaced with a constant one if time adjustment is not required. Resistor R5 can be replaced with another one with a resistance of 7.5-12.5 kOhm. It is better to leave resistors R6 and R7 unchanged. The capacitor can be replaced with another capacitance. But its tension cannot be reduced.
To make the timer work more clearly, I decided to assemble a simple tweeter. I didn’t etch the board, I collected everything on cardboard. A 50 ohm speaker is connected to this circuit, which can be taken from the handsets of Soviet telephones. You can place a button with the same capacitor in parallel with the capacitor, and when you press the button, the sound from the speaker will sound several tones lower.
I would like to remind you that in parallel with the diode you can turn on an electromagnetic relay with a winding current of no more than 50 mA (if you have KT315). And now a short video about the operation of the device:
With the ratings indicated in the diagram, the delay time is not long, but it can easily be increased by installing a capacitance of a larger rating. I assembled the circuit bkmz268.
Discuss the article SIMPLE TIMER DIAGRAM
Some people still use hourglasses to measure short periods of time. Watching the movement of grains of sand in such a watch is very exciting, but using it as a timer is not always convenient. Therefore, they are being replaced by an electronic timer, the diagram of which is presented below.
Timer circuit
It is based on the widely used inexpensive NE555 chip. The operating algorithm is as follows - when you briefly press the S1 button, a voltage equal to the circuit supply voltage appears at the OUT output and LED1 lights up. After a specified period of time, the LED goes out and the output voltage becomes zero. The timer operating time is set by trimming resistor R1 and can vary from zero to 3-4 minutes. If there is a need to increase the maximum delay time of the timer, then you can increase the capacitance of capacitor C1 to 100 μF, then it will be approximately 10 minutes. As transistor T1, you can use any bipolar transistor of medium or low power n-p-n structure, for example, BC547, KT315, BD139. Any button for closing without fixing can be used as button S1. The circuit is powered by a voltage of 9 - 12 volts, the current consumption without load does not exceed 10 mA.
Making a timer
The circuit is assembled on a printed circuit board measuring 35x65, the file for the Sprint Layout program is attached to the article. The trimmer can be installed directly on the board, or it can be wired and a potentiometer can be used to adjust the operating time. To connect power and load wires, the board has spaces for screw terminals. The board is made using the LUT method, several photos of the process:
Download the board:
(downloads: 252)
After soldering all the parts, the board must be washed from flux and the adjacent tracks must be checked for short circuits. The assembled timer does not need to be configured; all that remains is to set the desired operating time and press the button. A relay can be connected to the OUT output, in which case the timer can control a powerful load. When installing a relay in parallel with its winding, a diode should be installed to protect the transistor. The scope of application of such a timer is very wide and is limited only by the user’s imagination. Happy building!
Thanks to a time relay, you can seriously save money. For example, it can be installed in a closet, corridor or entrance; with one click you can turn on the light, and after a certain period of time it will turn off automatically. This time will be enough for you to find an item in the pantry or simply go through an area in the corridor. In this article we will tell you how to make a time relay with your own hands, consider step-by-step instructions and the simplest connection diagrams.
How to make a time relay - the easiest option
We understand that the bulk of our readers are amateurs. Therefore, we decided not to go into complex technical terms that can be confusing. Especially for our subscribers, we found this video, after watching which you can understand how to make a homemade timer to turn off the electricity.
We would like to draw your attention to the fact that you should not have any difficulties, because the instructions are extremely simple to understand.
To make a time relay we need the following materials: 
The time relay connection diagram looks like this: 
The capacitor here is C1. The delay time of such a relay is 10 minutes. If we talk about other characteristics of the kit, it boasts 1000 uF/16 Volts. The time is adjusted using a standard resistor R1. The device is controlled using contacts; there is no need to make a special board for it; it can be assembled as shown in the breadboard. 
Assembling a time relay based on the NE 555 timer
The second time relay circuit is also elementary. But, to assemble it, we need a NE 555 timer. This timer is designed to turn on and off various devices. Its diagram looks like this. 
The main component of this device is a microcircuit; it is used in the construction of the most popular electrical devices and timers. The microcircuit allows you to control the load using a special electromechanical relay. Therefore, you can configure it to turn the light off and on.
Controlling this timer is quite simple; on the body you will find two buttons:
- Start.
- Stop.
To start the time, you must press the “start” button. If you need to return to the original state, then click “stop”. Note that the time interval is controlled by resistor R1 and capacitor C1. The time after which a lamp or other lighting device goes out depends on their rating. You can set the time from two seconds to three minutes. So you can easily find the best shutdown time. This model requires constant power from a 12 Volt source.
You can learn more about it by watching this video.
We recommend reading: how to install a headlight strip.
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:
| Item name | Denominations |
| Transistor | KT937A(B) or ВD 876 |
| Any with 9–12 V power supply. |
|
| Resistor R1 | |
| Resistor R2 | |
| Variable resistor R3 | |
| Capacitor C1 | 25 V 3300 µF |
| Switch |
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.
Clock with audible alarm timer for controlling household appliances.
A timer is a device that turns equipment on or off at a set time with its switching contacts. Real-time timers allow you to set the trigger time at a set time of day. The simplest example of such a timer would be an alarm clock.
The scope of application of the timer is extensive:
- lighting control;
- watering management of home and garden plants;
- ventilation control;
- aquarium management;
- control of electric heaters and so on.
The proposed timer can be made quickly and inexpensively even by a novice radio amateur.
I made it based on the clock designer. ()
I needed to use a timer to control the watering of plants at the dacha.
Watch the entire manufacturing process in the video:
List of tools and materials
- any electronic watch with an alarm sound;
-screwdriver;
- scissors;
- soldering iron;
-cambric;
- two 12V relays;
-12V power supply from adapter;
- connecting wires;
- foil PCB for a printed circuit board or breadboard;
-industrial or homemade time relay;
-resistor;
- transistors KT815 (or analogues);
-diode.
Step one. Timer board wiring.
Timer circuit
All that is needed is to solder the components according to the diagram onto a breadboard and solder two wires from the piezo emitter of the clock. Let's assemble a simple circuit with an intermediate relay and a transistor switch. When the first pulse of a sound signal is sent from the clock, relay P1 is turned on, the normally open contact closes and turns on the load, and at the same time, through the second normally open contact of relay P1 and the normally closed contact of the time relay, relay P1 self-locks. Together with the load, the time relay PB is turned on - the countdown of the specified load operating time begins. At the end of this time, RV opens the contact and relay P1 is de-energized, the load is turned off. The circuit is ready for the next cycle. The diode serves to prevent a reverse pulse into the clock circuit (any low-power diode can be used). LED to indicate load activation. In this circuit, you need an intermediate relay with two normally open contacts, but I didn’t have it - I used two Chinese relays (the coils are connected in parallel). If the load is more powerful, then accordingly you need to use a relay with more powerful contacts. I had a 12V adapter and installed its circuit directly on the breadboard. In principle, any low-power 12V power source can be used.
In short, the clock turns on the load and the time relay is turned off after the delay has expired.
If you do not have an industrial time relay, you can make it yourself using a simple scheme. As the capacitance of capacitor C1 increases, the operating time of the relay increases.
Step two. Checking the timer operation.
My circuit worked the first time I turned it on.
All that remains is to set the alarm time. My watch has two alarm time settings. For my case, it’s enough to turn on watering, for example, in the morning at 7 o’clock for one hour, and in the evening at 20 o’clock, water again. When you press the clock buttons, sound signals are emitted, so when setting, the timer circuit must be de-energized to prevent false alarms. My watch has a “chime” function - every hour from 8 to 20 o’clock, that is, in addition to the alarm clock, you can use these signals if necessary. If not necessary, then the “chimes” function is disabled.
This is how the weekend design turned out. It was interesting to test out the new scheme, so everything was done quickly. In the future, it will be necessary to make a case and place a board and a time relay there. A beginner can make such a timer on his own without spending a lot of time and money. And where to use them is up to you to decide.
All the work took a couple of weekend evenings and 75 rubles (
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