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.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.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.To assemble the circuityou need:
Device diagramThe 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:
- NE555 IC - 1 pc.
- BC547 transistor - 1 pc.
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