How to convert stable and low voltage direct current into pulsed direct current

The landlord is estimated to be an outer door. I guess I still can't understand what I said upstairs, and I would like to add the two upstairs. The one on the first floor is about using a counter to control the switch of the transistor.

The transistor then controls the light emitting tube. This guy is wrong. The counter is for counting.

I think it's talking about signal generators. The 555 basic circuit can be used to make a pulse signal generator. The signal is transmitted to the base of the transistor.

Control tube switches. The light-emitting tube is connected to the collector. The cost is about two dollars.

The cost of the second floor is high. A single-chip microcomputer costs about six yuan. The landlord must not have fired the utensils.

Programming is even more cumbersome. It is recommended to use the ground floor. Find the 555 flashing light circuit

A lot. If you can't read the circuit, there's no way. Ready-made, after thinking about it, I don't seem to see where it is sold.

Because it's too simple.

Register + transistor switching circuit (preferably choose common base, the same phase).Fundamentals of digital and analog electricity.

Direct current"(Direct Current, abbreviated as DC), also known as"Constant current"In 1747, Franklin of the United States proposed the law of conservation of charge based on experiments, and defined the terms of positive and negative electricity.

A constant current means that neither the size (voltage) nor the direction (positive or negative) change over time (within a relative range), as in the case of a dry cell battery. Pulsating DC means that the direction (positive and negative) remains unchanged, but the size changes with time, for example: we get the typical pulsating DC after the 50Hz AC is rectified by the diode, and the half-wave rectification is 50Hz pulsating DC, if it is a full wave or bridge rectification, it is 100Hz pulsating DC, and they only become smooth DC after filtering (with inductance or capacitance), of course, there are still pulsating components (called ripple coefficient), The filtering effect of the magnitude and size filter circuits.

It is OK to output PWM with a single-chip microcomputer, and the principle of following the shooting base is used.

There are many ways to convert DC low voltage to high voltage.

1. Add low-voltage DC with a switch to chopper into pulsating DC and add voltage up to the transformer, and then rectify to obtain high-voltage DC.

2. The switch is added to the inductance, DC is added to the inductor and then the switch is disconnected instantly, and the high-voltage DC can be obtained on the inductor.

3 capacitors. Charge n capacitors, and then connect the capacitors in series to get n times the direct current.

All of these can now be done with electronic circuits. Technically, it's called a dc-dc transformation. Power banks belong to the second way.

First, the low-voltage DC is converted to low-voltage AC with an inverter, and then the voltage is boosted by a transformer, and then the rectifier is used to rectify the high-voltage DC.

To convert the AC voltage into DC voltage, it is necessary to use a rectifier diode, rectify the AC voltage into DC voltage, (it is best to use a 'bridge' rectification, so that the DC voltage ripple is small) and then filter with electrolytic capacitors, (i.e. ;Put the electrolytic capacitor on the rectified power supply, and pay attention to the positive pole of the electrolytic capacitor to the positive pole of the power supply, and connect the negative pole of the electrolytic capacitor to the negative pole of the power supply. It should also be noted that the withstand voltage of the electrolytic capacitor must be higher than the AC voltage before rectification.

More than 2 times the root number, such as; AC is 220 volts, and the withstand voltage of electrolytic capacitors is best 400 volts. In order to avoid the danger that the electrolytic capacitor will be broken down if the withstand voltage is not enough! In this way, the alternating current becomes direct current.

How to distinguish between AC voltage and DC voltage?

The easiest way.

Measured with a multimeter, if the DC voltage is used to measure the alternating current, the multimeter does not respond. If the DC voltage is used to measure the direct current, the multimeter has a normal indication, then, the red watch pen is connected to the positive pole, and the black watch pen is connected to the negative pole; If the red pen is connected to the negative pole and the black pen is connected to the positive pole, the hands of the multimeter will start in reverse. (i.e. move to the left).

Single-phase bridge rectifier circuit as shown in the figure, four diodes as rectifier devices connected into a bridge form, when the polarity of the transformer TR is positive and the lower end is negative, VS1, VD3 due to forward bias and on, VD2, VD4 due to reverse bias and cut-off, there is a current through the load RL, the current is returned to the lower end of the transformer by VD1, RL, VD3 by the upper end of the transformer secondary winding, a half-wave rectification voltage is obtained on the RL, when the polarity of the power supply is opposite, the rectifier device VD2, VD4 is turned on, VDL and VD3 are cut-off, and the current is returned to the upper end of TR through VD2, R1 and VD4, so that a half-wave rectification voltage is also obtained on RL. By repeating this, a voltage waveform can be obtained on the load RL that is the same as that in the case of single-phase full-wave rectification.

Bridge rectification is more common.

First, the transformer is used to convert the high-voltage alternating current into low-voltage alternating current, and then the diode is used to convert the low-voltage alternating current into low-voltage pulsed direct current, and then the pulsed direct current is converted into stable direct current with a capacitor and a three-terminal voltage stabilizing integrated circuit. Let's take a look at the picture below.

1. Step-down with transformer. 2. Rectify with rectifier.

Because in the process of current transmission, through the resistance of the wire, a part of the current is converted into heat and is lost, this loss is proportional to the size of the current, the larger the current transmitted, the more the loss, in order to reduce the loss, try to reduce the current and the power conveyed can not be less, so that the voltage of the transmission needs to be improved, in the case of the voltage rises, the transmission power is kept unchanged, the current can be reduced at the same time, so that the loss of resistance is also reduced, so that the power loss of the power of the conveyed is reduced. In the early days, the power transmission was high-voltage AC, and later with the development of science and technology, the loss of DC transmission was lower than that of AC transmission, so it is widely used in long-distance ultra-high-voltage DC transmission.

The mid-end voltage of electricity in China is AC 380 220 volts and 10 kV, the ultra-high voltage transmission voltage is 220 kV AC, and the DC is 500 kV, so the voltage must be lowered, and the DC transmission also needs to be inverted, and the appropriate voltage can be provided to the terminal equipment after several stages of step-down.

The first conversion to high voltage is to reduce the energy loss in the transmission process and save energy, because due to the resistance of the wire, in the transmission process, the two ends of the wire should share a part of the voltage, in order to reduce the transmission voltage loss and power loss, long-distance transmission usually uses high-voltage transmission, and the conversion back is for power supply, the home is used with a low voltage of 220 volts, and the high voltage will be electrocuted!

The circuit diagram of AC 220V output DC 24V is as follows:

In the figure, T1 is a step-down transformer, which is used to reduce the voltage of alternating current. D1-D4 is to dismantle and call four 1N4007 rectifier diodes, and turn the alternating current into a non-smooth direct current through the four Lukai rectifier diodes. C1 is the filter capacitor, which makes the DC faster and smoother, and the LM7824 is the three-terminal regulator bridge vertical, with an output of 24V DC.