One-button power on and off

Many household electrical appliances, be they stereos, televisions, various fixtures, are turned on and off by pressing the same button. He 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 building improvised amplifiers in elegant cases, a device with this principle of switching on and off looks already much more perfect, resembling a factory instrument.
Switching the load on and off with one button

Device diagram

The switch on and off loading mode with one button is shown below. It is simple as a boot, does not contain scarce components and starts immediately. So, the scheme:
Switching the load on and off with one button
Its key element is the popular NE555 timer chip. It is she who registers the keystroke and sets at the output either a logical 1 or 0.Button S1 - any button on the closure without fixing, because through it there is practically no current flow, there are practically no requirements for the button. I took the first available, Soviet 60's.
Switching the load on and off with one button
The capacitor C1 and the resistor R3 suppress the bounce of the contacts of the button, C1 it is best to use a non-polar ceramic or film. LED1 indicates the status of the load - the LED is on, the load is on, off - off. The transistor T1 switches the relay coil, here you can use any low-power transistor of the NPN structure, for example, BC547, KT3102, KT315, BC184, 2N4123. A diode standing parallel to the relay coil serves to suppress the self-induction pulses arising in the winding. 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 winding the relay. In this case, it is worthwhile to put a transistor more powerful, for example, KT817, and the diode can be excluded.


Switching the load on and off with one button
To assemble the circuityou need:
  • NE555 IC - 1 pc.
  • BC547 transistor - 1 pc.

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