Use an RC oscillator composed of 555 chips to make a multimeter

The electric field can reach its maximum, the magnetic field energy is zero, and the induced current in the loop is i=0. Discharge completed (charging started): the electric field energy is zero, the magnetic field can reach the maximum, and the induced current in the loop reaches the maximum.

The charge on the capacitor plate, the current passing through the coil, and the magnetic and electric fields associated with the current and charge all change periodically, and this phenomenon is called electromagnetic oscillation.

The electric field energy increases, the magnetic field energy decreases, the current in the loop decreases, and the amount of electricity on the capacitor increases. From the point of view of energy: the magnetic field energy is converted into the electric field energy.

The electric field energy decreases, the magnetic field energy increases, the current in the loop increases, and the amount of electricity on the capacitor decreases. From the point of view of energy: the electric field energy can be converted into the magnetic field energy.

In the process of generating an oscillating current in an oscillating circuit.

A very simple circuit, properly adjust the parameters of W1, R1, and C1 in the diagram to achieve a frequency of 50Hz.

If you want a duty cycle of 50%, you need to add two diodes.

There is a formula that specifically calculates its frequency.

The circuit that generates the 1-second signal.

The second signal generation circuit consists of a multivibrator consisting of an integrated circuit 555 timer and an RC. The chips needed are IC 555 timers, as well as resistors and capacitors. The following diagram shows its circuit diagram:

The oscillation circuit is the core part of the digital clock, and its frequency and stability are directly related to the accuracy of the watch. Therefore, a multivibrator composed of a 555 timer is selected, in which the capacitance C1 is 47 microfarads, C2 is the microfarth, and the two resistors R1=R2=10K ohms. At this point, a periodic rectangular wave is obtained at the output of the circuit, and its oscillation frequency is:

f=(3-1) is substituted by the equation (3-1) for R1, R2 and C, F=1Hz. That is, its output frequency is 1 Hz rectangular wave signal.

This requires you to have a very accurate stopwatch to send signals to the 555 oscillator for proofreading, and to finely adjust the oscillator timing resistance. When the tuning is almost in sync for a few hours, it's fine. Also, note that this oscillator needs to pay attention to pulse width control.

NE555 usually makes oscillators below 300kHz, and it is not possible to make 500k to do it, but I am afraid that it will not work to do 1000k, so I should switch to the 7555 chip of CMOS products. C1 uses 100pf, R1 uses 1k, R2 is about a few ks (1000kHz) to a dozen ks (500kHz), and it needs to be debugged.

Principle: At the moment when the circuit is connected to the power supply, because the capacitor C is too late to charge, VC=0V, the output VO is high. At the same time, the collector output (7 pins) is disconnected from the ground, the power supply VCC charges the capacitor C, and the circuit enters a temporary steady state, after which the circuit generates periodic output pulses over and over again.

The maintenance time of the two transient steady states of the multivibrator depends on the parameters of the RC charge and discharge circuits. The maintenance time of the steady-state state, i.e., the forward pulse width t1 of the output VO; The duration of the steady-state state, i.e., the negative pulse width t2 of the output VO.

Therefore, the oscillation period t=t1+t2=, and the oscillation frequency f=1 t. The ratio of the forward pulse width t1 to the oscillation period t is called the duty cycle d of the rectangular wave, and d = (r1+r2) (r1+2r2) can be obtained from the above conditions, and if r2 is >> r1, then d 1 2, that is, the rectangular wave (square wave) with the same positive and negative pulse width of the output signal.

Introduction: A multivibrator uses deep positive feedback to make two electronic devices alternately turn on and off through resistor-capacitance coupling, so as to self-excite an oscillator with square wave output. It is often used as a square wave generator.

A multivibrator is a self-excited oscillator that can generate a rectangular wave, also known as a rectangular wave generator. There is no steady-state for multivibrators, only two temporary steadies. During operation, the state of the circuit automatically alternates between these two transient steady states, resulting in a rectangular wave pulse signal, which is often used as a pulse signal source and a clock signal in a sequential circuit.

The 555 timer has low cost and reliable performance, and only needs to connect a few external resistors and capacitors to realize pulse generation and conversion circuits such as multivibrators, monostable flip-flops and Schmitt flip-flops. It is also widely used as a timer in instrumentation, household appliances, electronic measurement and automatic control.

It consists of two voltage comparators, three 5k ohm equivalent series divider resistors (hence the name of the 555 timer), an RS flip-flop, a discharge tube T, and a power output stage. It offers two reference voltages, VCC 3 and 2VCC 3

Electronic DIY complementary audio multivibrator circuit principle and working process.

What is the difference between the output high level and the power supply. There are many 555 manufacturers, and there are different models of the same manufacturer, and the working voltage range, power consumption, output level, and driving ability of each model are different.

The output of the 555 multivibrator is equal to the positive and negative pulse width, which is t1 = t2 = seconds = seconds.

Oscillation period and frequency.

t=t1+t2=2 seconds=seconds.

f=1/t=

The RD terminal stops vibration when it is connected to a low level.