Why does the capacitor charge and discharge, which plays the role of time delay?

Because the two poles of the capacitor are separated from the insulator, two different charges attract each other, and have the effect of storing the charge, so that it can be charged and discharged, but the charging and discharging time is short, usually about seconds, and the AC resistance DC effect, in the AC power to DC power, it plays a filtering role, so that the current and voltage are stable, and when the AC power can be alternated, the two plates store different charges, and when the current direction period changes, it will be discharged, so as to delay the current.

The principle of capacitor charging and discharging is:

When the capacitor is turned on the power supply, the force in the electric field.

Under the effect, the capacitor plate is connected to the positive pole of the power supply.

The passing power supply is moved to the plate connected to the negative pole of the power supply, the positive electrode is positively charged due to the loss of negative charge, and the negative electrode is negatively charged due to the negative charge, and the charges carried by the positive and negative plates are equal in magnitude, and the signs are opposite. The directional movement of the charge forms an electric current, which is maximum at the beginning and gradually decreases later due to the repulsion of the same charge. In the process of charge movement, the charge stored in the capacitor plate is constantly increasing, and the charge stops moving when the voltage UC between the two plates of the capacitor is equal to the power supply voltage U, the current i=0, the switch is closed, and the charge of the positive and negative plates of the capacitor is neutralized by the connection of the wire.

When k is closed, the capacitor c is positively charged.

The negative electrode can be moved to neutralize and fall, and the negative charge of the negative electrode can also be moved to the positive electrode to neutralize and fall, and the charge gradually decreases, showing that the current decreases, and the voltage gradually decreases to zero.

A capacitor is a charge that gathers electricity, you can think of it as a water cup, and charging and discharging is charging and discharging water.

During the charging process, the voltage rises slowly, and the discharge is the opposite.

You only need to detect the voltage across the capacitor to achieve the time delay.

For example, when charging, the voltage at both ends of the capacitor is zero at the beginning, and as the charging time is extended, the voltage gradually rises to the voltage you set, and you can control the switch of the circuit.

Of course, it is also possible to use the discharge in reverse.

The delay time is related to capacitance capacity, capacitance leakage, charging resistance, and voltage, and sometimes the load resistance.

This is actually not very complicated, you can go to the hard city to see if there is this model, if there is, you can find its technical information on it.

1) The subheadings of both delay circuits correctly state the function of the circuit;

2) When powering on, to make the light on, you must press the switch first, and the power supply will quickly charge the capacitor through the diode, so that UA starts UA=VCC, and after rapid full charge, UA=on-voltage of the diode), at the same time, because the UA voltage is lower than the emitter voltage, the triode is on, and the light is on;

After the switch is disconnected, the capacitor will be discharged through the transmission junction and resistance R2, and the base current can still be maintained, the triode remains on, the light is on, and the discharge time depends on the product of C and R2;

It can be seen that this circuit is composed of charging the capacitor quickly and then slowly discharging the capacitor;

When powering up, the first gate circuit is connected to the ground because the input terminal is connected to the resistor, relative to the input low level, then the output is high after the non gate, that is, ua=vcc, and because the capacitor has not been charged, the voltage ub is low, then the output high level after the NOT gate, the light is on;

Then, because UA>UB and the diode is not on, the power supply charges the capacitor through R2, so that UB slowly increases, and when UB rises to the input threshold of the gate circuit, the output of the non-gate circuit will be flipped, and the output will change from high to low, and the light will be turned off. Finally ub=vcc;

When the switch is pressed, the first gate circuit is flipped over, and the output is low, that is, ua=0, at this moment, ua can be seen that the circuit is charging the capacitor slowly, and then the capacitor can be discharged quickly;

1. The length of capacitor charging and discharging time should be analyzed according to the specific situation, and the explanation is as follows;

2. It is necessary to determine whether there is a constraint on the peripheral circuit of charging and discharging, and the general simple ** circuit is based on this principle.

3. The charging and discharging time is controllable;

4. The charging and discharging time of the capacitor depends on the following three factors: the charging power supply voltage or the initial voltage of discharge, the capacity of the capacitor and the size of the circuit resistance;

5. In the case of the same voltage, for the same capacitance, it is only determined by the loop resistance;

6. If the resistance of the circuit is larger during charging and the resistance of the circuit is smaller when discharging, then the charging time will be longer than the discharge time.

1. The length of capacitor charging rotten ruler and discharge time should be analyzed according to specific circumstances, and explained as follows;

2. It is necessary to determine whether the peripheral circuit of charging and discharging is constrained, and the general simple ** circuit is based on this original cover posture;

3. The charging and discharging time is controllable;

4. The charging and discharging time of the capacitor depends on the following three factors: the charging power supply voltage or the initial hungry high voltage of the discharge, the capacity of the capacitor and the size of the loop resistance;

5. In the case of the same voltage, for the same capacitance, it is only determined by the loop resistance;

6. If the resistance of the circuit is larger during charging and the resistance of the circuit is smaller when discharging, then the charging time will be longer than the discharge time.

The charging and discharging process of a capacitor.

When the capacitor is connected to the DC power supply, the charge on the metal plate connected to the positive pole of the power supply will run to the metal plate connected to the negative pole of the power supply under the action of electric field force, so that the metal plate connected to the positive pole of the power supply loses its charge and is positively charged, and the metal plate connected to the negative pole of the power supply gets the charge negatively charged (the charge of the two metal plates is equal in size, the sign is opposite), and the capacitor begins to charge.

In the circuit, the movement of the charge forms the current, and due to the repulsion of the same charge, the current is maximum at the beginning of the charge movement and gradually decreases thereafter; In the process of charge movement, the charge gradually increases, and the voltage between the two metal plates gradually increases, and when it increases to the same as the power supply voltage, the current decreases to zero after charging.

Capacitor discharge process.

When the charged capacitor is located in a closed path without power supply, the charge on the negatively charged metal plate will run to the positively charged metal plate under the action of electric field force, so that the positive and negative charges are neutralized, and the capacitor begins to discharge.

In the circuit, the movement of the charge forms an electric current, which is maximized at the beginning of the discharge process and gradually decreases due to the attraction of the opposite charge; The capacitor charge is maximum at the beginning of the discharge process, and then gradually decreases, and when the charge decreases to zero, the discharge is completed and the current decreases to zero.

Since no current flows through the circuit after the capacitor is charged, the capacitor acts as a DC block, which can be considered an open circuit in a DC circuit.

The process of making the two poles of the capacitor with the same amount of different charges: the charging current is from large to small; The amount of capacitor charge increases; The voltage between the plates increases, and the electric field strength increases. Electrical energy is converted into electric field energyThe process of making a charged capacitor lose its charge:

The discharge current is from large to small; The charge of the capacitor decreases; The voltage between the plates decreases, and the electric field strength decreases. The electric field energy is converted into other forms of energy.

Ideally, when the two poles of a capacitor are connected to both ends of a 220V AC power supply, the current in the capacitor is at an angle of 90 degrees to the voltage across the capacitor, and the current is 90° ahead of the voltage. In the non-associative case, it is less than 90° (usually close to 90° due to the small capacitance loss). In addition, since the frequency of the power grid is 50Hz, it means that it will change 50 times in a second according to the sine wave.

The voltage zero crossing on the capacitor is synchronized with the power grid, and the voltage zero crossing is an instantaneous action, although there are 100 zero crossings in a second, you can hardly disconnect the capacitor from the power supply at the moment of voltage crossing. That's why the capacitor is almost always charged when disconnected from the power supply.

Attention should be drawn to:

The withstand voltage of the capacitor should not be lower than AC 250V, and the withstand voltage selection reduces the risk of bursting of the capacitor.

2.The main safety protection must be taken during operation (potatoes must wear insulating gloves) 3It is best to connect the capacitor in series to a power switch, and then connect it to the 220V AC wheel bracelet source for relevant tests.