Pulse width modulation

Modulation (Latin modulatio - regularity, rhythm) is the process of changing a carrier signal using an information or modulating signal; in life there are various types of modulation, for example, in radio communications they use amplitude (AM) and frequency modulation (FM), from the name it is obvious that in In one case the amplitude changes, and in the other case the frequency changes.
Information transfer occurs by changing the modulated CARRIER signal with the help of a modulating signal.
ШИМ сигнал сформированный с помощью синусоиды.jpg
ШИМ сигнал сформированный с помощью синусоиды.jpg

NE555 chip design

NE555 is one of the best-selling microcircuits in the world, which was released in 1971, at its core it is a UNIVERSAL TIMER that can generate single or repeating pulses, the characteristics of which depend on the wiring of the microcircuit.

The wiring of a microcircuit is a set of radio components (capacitors and resistors) necessary for the microcircuit to operate in the mode we need. Those. any microcircuit is a complex and large set of components, so inside the NE555 there are about 20 transistors, 15 resistors and 2 diodes, all of them are made for the versatility of the solution, and developers can already put the desired capacitor on certain contacts and get the desired signal

Each microcircuit has a KEY indicating the first contact, as a rule, the key is a point in the body adjacent to one of the legs or a semicircular depression between the first and last contacts, as in the case of the NE555 chip

1 contact - MINUS power supply from 4.5 to 16.5 volts
Pin 2 - RUN When the voltage on this pin drops below 1/3 of VCC, the output goes high and the timing begins
Contact 3 - OUTPUT here we get our signal for further use
Pin 4 - RESET A high voltage level at this input (more than 0.7 V) allows the timer to start, otherwise the start is prohibited
Pin 5 - CONTROL determines the stop and start thresholds
6 pin - STOP when the voltage at this pin exceeds the voltage at the CTRL pin, the output voltage is set to a low level, the interval ends
Pin 7 - DISCHARGE Open collector type output, typically used to discharge the timing capacitor between intervals
Pin 8 - PLUS power supply from 4.5 to 16.5 volts
Таймер NE555.jpg

Duty ratio control

This circuit uses a “setting” capacitor C1 and a variable resistor RP1, which are used to set the shape of the output signal according to the following formula
t (pulse time) = 1.1 * C * R

If you need a pulse 1 second long, then you need to take a 22 kOhm resistor and a 47 μF capacitor; the same duration will be if you increase the resistor resistance 10 times to 220 kOhm and REDUCE the capacitance of the capacitor to 4.7 μF.
Схема включения таймера для регулировки скважности.jpg

Frequency control

Unlike the first circuit, where we adjusted only the duty cycle, in the second circuit we can now adjust not only the duty cycle and frequency using the second variable resistor RP2, otherwise the circuit repeats our first version, where we only adjusted the duty cycle.
Изменение частоты с помощь. дополнительного переменного резистора.jpg
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