Single button load switches on the chip 222

The 222-microcircuit project described earlier in [1-3] is an analog of the 555 microcircuit. Her main purpose is the generation of rectangular pulses with an adjustable fill factor and independent frequency control. Such a chip is not produced industrially, although it is not difficult to assemble its layout using two comparators and five resistors, Figure 1. The pin configuration and functions chip and the typical circuit of its inclusion are also shown. There are several devices for which the 222 chip can be used, these are also given in [1-3].

Figure 1 The internal structure of the project of the chip 222, its pin configuration and functions and a typical circuit of inclusion.

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On the basis of the chip 222, simple switching devices can be created, which are turned on by briefly pressing the start button. The device is turned off by pressing the same button for a longer time. Figure 2 shows a diagram of such a device.

Figure 2 Switching device controlled by one button.

In the initial state, a fixed voltage is applied to the input Cx of the chip (pin 2) from the resistive divider R1, R2. The voltage at the control input ADJ (pin 5 of the chip) is zero. The voltage at the PWM output (pin 4) is also zero. Transistor Q1 is closed, the load Rload is de-energized. The capacitor C1 is charged via the contacts of the button S1 to the supply voltage of the device. When the S1 button is briefly pressed, the voltage from the charged capacitor C1 enters the ADJ input (pin 5 of the chip). The voltage at the PWM output (pin 4) increases to the supply voltage of the device and through the resistor R3 enters the input ADJ (pin 5) of the chip. The state of the chip is fixed, a constant high voltage level appears at its output and remains. When transistor Q1 switches its state, the load is connected to the power source.

In order to turn off the load, it is necessary to press the S1 button again, holding it in the pressed position for a longer time. Capacitor C1 will discharge to resistor R5 and R6 to a voltage below the switching voltage of the chip 222, the device will return to its original state.

The second version of the device, Figure 3, works on a different principle. When the S1 button is pressed, the U1 222 chip the state is being switched, the load is connected to the power source. You can return the device to its original state by briefly pressing the S2 button. Formally, this is a two-button device that performs the role of a thyristor.

Figure 3 A pseudo-thyristor device on a 222 chip.

The following Figure 4 shows a combined load control scheme. You can enable and disable the load by pressing the S1 button for a short or long time. Also, the load can be turned off by a short-term reset of the supply voltage when pressing the S2 button.

Figure 4 Is a combined device for push-button switching on and off of the load using the 222 chip.

Michael A. Shustov is a doctor of technical sciences, candidate of chemical sciences and the author of over 750 printed works in the field of electronics, chemistry, physics, geology, medicine, and history.

Related Content


  1. Shustov M.A. “Chip 222 – alternative 555. PWM generator with independent frequency control”, International Journal of Circuits and Electronics, 2021, V. 6, P. 23–31. Pub. Date: 06 September 2021.
  2. Shustov M.A. “Adjustable threshold devices on a chip 222”, Radioamateur (BY), 2023, No. 6, pp. 20–21.
  3. Shustov M.A. Digital circuitry from the basics to the creation of practical devices. – St. Petersburg: Publishing House “Science and Technology”, 2024. 560 p. (165×235 mm). The circulation is 1200 copies. ISBN 978-5-907592-36-0.


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