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Many household electrical appliances, whether it be music centers, televisions, various lamps, turn on and off by pressing the same button. Pressed once - the device turned on, pressed again - turned off. In amateur radio practice, it is often necessary to implement the same principle. Such buttons are often used in the construction of home-made amplifiers in elegant cases, a device with this principle of turning on and off looks already much more perfect, resembling a factory device.
One-button load on and off

Device diagram


The scheme of switching on and off the load with one button is presented below. It is simple as a felt boot, does not contain scarce components and starts immediately. So the diagram:
One-button load on and off

Its key link is the popular NE555 timer chip. It is she who registers the keystroke and sets the output to either logical 1 or 0. Button S1 - any button to close without locking, because almost no current flows through it, there are practically no requirements for the button. I took the first Soviet one from the 60s.
One-button load on and off

Capacitor C1 and resistor R3 suppress the bounce of the button contacts, C1 is best used non-polar ceramic or film. LED1 indicates the status of the load - the LED is on, the load is on, off, off. Transistor T1 commutes the relay winding, here you can use any low-power transistor of NPN structure, for example, BC547, KT3102, KT315, BC184, 2N4123. A diode standing parallel to the relay coil serves to suppress self-induction pulses that occur in the coil. You can use any low-power diode, for example, KD521, 1N4148. If the load consumes a small current, you can connect it directly to the circuit instead of the relay coil. In this case, it is worth putting the transistor more powerful, for example, KT817, and the diode can be excluded.

Materials


One-button load on and off

To build the circuit you will need:
  • Chip NE555 - 1 pc.
  • BC547 Transistor - 1 pc.
  • Capacitor 1 uF -1 pc.
  • Resistor 10 kOhm - 2 pcs.
  • 100 kOhm resistor - 1 pc.
  • 1 kOhm resistor - 2 pcs.
  • Button without fixing - 1 pc.
  • KD521 diode - 1 pc.
  • 3v LED - 1 PC.
  • Relay - 1 pc.

In addition, you need a soldering iron, flux, solder and the ability to assemble electronic circuits. Electronic components cost almost a penny and are sold at any radio parts store.

Device assembly


First of all, it is necessary to make a printed circuit board. It is performed by the LUT method, the file is attached to the article. It is not necessary to mirror before printing. The LUT method has been repeatedly described on the Internet; learning it is not so difficult. A few photos of the process:
Download board:
[5.04 Kb] (downloads: 944)

One-button load on and off

One-button load on and off

One-button load on and off

One-button load on and off

One-button load on and off

If there is no printer at hand, you can draw a printed circuit board with a marker or varnish, because it is quite small. After drilling the holes, the board must be tinned to prevent oxidation of the copper tracks.
After making the board, you can begin to solder the parts into it. First, small components are soldered - resistors, diodes. After that, capacitors, microcircuits, and everything else. The wires can either be soldered directly to the board, or connected to the board using terminal blocks. I brought the power and OUT contacts for connecting the relay through the terminal blocks, and soldered the button directly to the board on a pair of wires.
One-button load on and off

Thus, this board can be integrated into any device, be it an amplifier, a home-made lamp, or anything else that requires turning on and off with one button without fixing.The network has many other similar circuits built on Soviet microcircuits, transistors, however, this circuit using the NE555 microcircuit has established itself as the simplest and most reliable at the same time.
One-button load on and off

One-button load on and off

Watch the video


The principle of operation is clearly shown in the video.
come back
Comments (17)
  1. Guest Fedor
    #1 Guest Fedor Guests April 8, 2018 18:48
    1
    The diode is placed parallel to the relay coil, for other purposes. To protect against breakdown of the key transistor. Since in the inductance (relay coil) the voltage is ahead of the current.
    1. Guest Michael
      #2 Guest Michael Guests April 8, 2018 8:26 p.m.
      1
      Both the author and Fedor say the same thing about the diode but in different words because the transistor breaks through the EMF of self-induction, which is many times more than the supply voltage.
  2. hippopotamus
    #3 hippopotamus Guests April 8, 2018 10:05 p.m.
    3
    what do you teach beginners? there are three jumpers on a board with two parts.
  3. Alexander
    #4 Alexander Guests April 9, 2018 19:48
    0
    All this in the presence of standby power 12 Volts, which is not advisable. The duty room must be done 5 Volts, any charger for a smartphone will pull
  4. Yuriyod1979
    #5 Yuriyod1979 Guests April 22, 2018 09:41
    1
    I do not need 5 volts! 12 just right! In the car, then!
  5. totiks
    #6 totiks Guests July 6, 2018 1:28 p.m.
    0
    Thanks, I was just looking for a similar design!
  6. Denis SunTi
    #7 Denis SunTi Guests August 28, 2018 01:43
    1
    And I didn’t understand something, where is the relay in the finished device? There is a diagram, there are necessary details, but not on a printed circuit board and in a finished device. In fact, it turns out that the button only turns on / off the LED, and power is supplied to the load regardless of whether the button is connected or not.
    1. iglitsa
      #8 iglitsa Guests January 31, 2019 10:56 p.m.
      0
      and really, it turned out funny. I was also looking for a relay =)
      the finished board has 2 paired terminals - input and output. and so it is necessary to connect a relay to the output
  7. Guest Sergey
    #9 Guest Sergey Guests January 2, 2019 10:42
    2
    Thank you for the circuit, but there is a drawback in it, it’s better to pull pin 5 of the microcircuit to the ground through a capacitor, so you can get rid of false positives.
    Used on the pump control circuit, tired of the constant operation, sometimes when the power is turned on, sometimes from interference in the network.
    Modeling in multisim showed that the circuit with an open 5 pin. When power is applied abruptly, it remains off. If a filter in the form of a capacitance is installed at the power input, the supply voltage increases more slowly and the circuit acquires an on state.
    If the 5th output is connected via a capacitor, then the circuit is turned on only when the button is pressed.
    1. Guest Alex
      #10 Guest Alex Guests January 18, 2019 6:53 a.m.
      0
      What capacity is the best capacitor to put
  8. Guest Sergey
    #11 Guest Sergey Guests January 27, 2019 08:44
    0
    What capacity should the capacitor put on the 5th leg of the NE555 chip
  9. Vitaliy Nezhelsky
    #12 Vitaliy Nezhelsky Visitors February 6, 2019 2:21 p.m.
    1
    This device does not work. everything is assembled according to the scheme from serviceable parts. there are no errors in installation. No snot. when you touch your 6th and 7th legs with your finger, there is a rattling sound for switching on and not sure switching on the reels. wants to turn on and does not want to - does not turn on. xs what's wrong. in comments it was said for a five-leg resistor to the ground .. what is the nominal value to put about? 1 to be enough?
  10. Vitaliy Nezhelsky
    #13 Vitaliy Nezhelsky Visitors February 6, 2019 2:22 p.m.
    0
    I apologize ... not a resistor .. what kind of capacitor should I put ???
  11. Guest Alexander
    #14 Guest Alexander Guests April 21, 2019 12:31
    0
    Thanks for the circuit, everything works fine, but with 5 feet on the ground the conder set 0.1 microfarads. but without it, everything also works.
  12. Albert
    #15 Albert Guests May 5, 2019 8:31 p.m.
    0
    why do you mislead people, your scheme is not working so much time killed for this omno which is not.
    1. iv
      #16 iv Guests July 29, 2019 12:57
      0
      under the transistor, the circuit board is not correctly drawn,
  13. Guest Gennady
    #17 Guest Gennady Guests August 1, 2019 1:54 PM
    0
    The circuit does not work when controlling inductive load (the fan turns on stably, and turns off after a few clicks on the button although the relay clicks), when controlling the bulb, everything works stably. Tell me what could be the reason.

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