Design of a microcontroller to control the light emitting of the diode 30

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Summary. Light-emitting diodes are generally used as indicator lights, for example, the computer's hard disk light flashes to indicate that your hard disk is working (if it does not flash, it is likely that your machine is too busy or in standby), and there are some indicator lights on the Walkman, as well as the indicator light of the charger. The forward conduction voltage of light-emitting diodes is larger than that of other diodes, and it is generally in the middle of the day.

two other diodes are generally in germanium tubes), silicon tubes). Rectifier diodes, which are also very common, take advantage of the unidirectional conduction characteristics of the diode, so that the negative polarity electrical signal can be filtered out--- half-wave rectification, and other rectifications can also be carried out--- such as full-wave rectification.

Light-emitting diodes.

Light-emitting diodes are generally used as indicator lights, for example, the computer's hard disk light flashes to indicate that your hard disk is working (if it does not flash, it is likely that your machine is too busy or in standby), and there are some indicator lights on the Walkman, as well as the indicator light of the charger. The forward conduction voltage of light-emitting diodes is larger than that of other diodes, and it is generally in the middle of the day. two other diodes are generally in germanium tubes), silicon tubes).

Rectifier diodes, which are also very common, take advantage of the unidirectional conduction characteristics of the diode, so that the negative polarity electrical signal can be filtered out--- half-wave rectification, and other rectifications can also be carried out--- such as full-wave rectification.

The diode also has a voltage stabilizing effect, because when the diode is turned on in the opposite direction, in the case of the diode being broken down, its current will increase instantaneously, so that when the external voltage increases, the increased current after the diode is broken down will pass through the diode and will not pass through the load connected in parallel with the diode, so that the device connected in parallel with it can be protected. The common one is to protect the FET, that is, to connect a diode in the opposite direction of the gate of the FET. The breakdown voltage of the diode is generally between 4V and 7V

Clamping function: clamping effect is to use the forward conduction voltage of the diode to maintain the germanium tube after conduction), silicon tube), so that the voltage at both ends of the device connected to it is maintained in a range, the simplest is that the BE junction voltage of the triode can be maintained at the clamping voltage when it is turned on, which is often used for the static analysis of the triode. Generally, there is no special description for silicon tubes and germanium tubes.

The LEDs are available in five packages:

1.Soft package.

The chips are directly bonded to a specific PCB printed board, connected into a specific character or display form by solder wires, and the LED chips and bond wires are protected with transparent resin and assembled in a specific housing. This type of encapsulation is commonly used in products for digital displays, character displays, or scrambled displays.

2.Pin package.

It is common to fix the LED chip on the 2000 series lead frame, solder the electrode lead, and encapsulate it into a certain transparent shape with epoxy resin to become a single LED device.

3.SMD packaging.

The LED chip is bonded to a miniature lead frame, and after the electrode leads are soldered, they are injection molded, and the glossy surface is generally encapsulated with epoxy resin.

4.Dual in-line package.

The chip is fixed with a copper lead frame similar to IC packaging, and the electrode leads are soldered and then encapsulated with transparent epoxy.

5.Power package.

There are also many packaging forms of power LEDs, which are characterized by a large bottom cavity of the bonded chip, and specular reflection ability, high thermal conductivity, and low enough thermal resistance to make the heat in the chip be quickly drawn out of the device, so that the chip and the ambient temperature to maintain a low temperature difference.

Extended information: LED packaging refers to the packaging of light-emitting chips, which is quite different from integrated circuit packaging. The packaging of LEDs requires not only the ability to protect the wick, but also the ability to transmit light. Therefore, the packaging of LED has special requirements for the packaging material.

Most of the LED packaging technology is developed and evolved on the basis of discrete device packaging technology, but it has great particularity. In general, the die of the discrete device is sealed in the package, and the function of the package is mainly to protect the die and complete the electrical interconnection bridge. The LED package is to complete the output of electrical signals, protect the die to work normally, and output:

The function of visible light has both electrical parameters and optical parameters, and the design and technical requirements of optical parameters cannot be easily used in the packaging of discrete devices for LEDs.

This one. This one. The circuit diagram is wrong!

Resistors play a very important role in light-emitting diode circuits, which is to limit the current!

So add a resistor in front of 2 as well.

Add a resistor in the middle of 3 and 4 as well!

This ensures that the current on each LED circuit is limited to the appropriate range!

1] The easiest is to buy two colors of light-emitting diodes for a few cents a small circuit board, also known as (hole board) The size is generally less than 10 yuan Small switch within one yuan 】] The hardware is not pulled.

2] Wiring* Insert the diodes into the circuit board one by one, and pay attention to the long legs of the diodes in the same direction, because the diodes are forward and reversed. And then the feet of the diodes are followed by the short legs of the first one and the long legs of the next one, and so on, and so on, and the red and blue pins are joined together, and finally, there are two pairs of threads.

3] Power supply Count how many red colors of the diode general voltage and current 3ma Find someone who understands the circuit and calculate the voltage and current you need Buy a small transformer and it's done.

4] Of course, you can also consider using a single-chip microcomputer to achieve control for a while and a half, you can't play if you want to use it, search a lot of **high points on the Internet.

1. Red and blue LED light-emitting tubes are purchased in the same quantity, it is recommended to buy a bag, there is a bag of 1,000 pieces, which is much cheaper.

2. Make flash control circuits, there are special warning light flash controllers on the market for sale, find a lot of them on the market, you can also make them, the use of simple state switching circuits is not good, it is recommended to use single-chip microcomputer production.

3. Battery-powered.

Isn't it just three empty circuit boards, red and blue LEDs.

The circuit is small for four dollars, and the big one is eight dollars, and the light-emitting diodes are sold online for 1-4 cents a piece.

The circuit is correct.

The landlord's circuit is to light up the diode when the output level is high, which is to add a "source current" load to the single-chip microcomputer.

However, the general single-chip microcomputer, when the output is high, does not have the ability to output current, so it needs to be assisted by an external "pull-up resistor".

The light-emitting diode emits a high light-emitting voltage, which can be calculated as 2V, and a pull-up resistor of 1K can produce a current of 3mA.

So, this circuit is correct.

However, if the output level is low and the diode is not allowed to emit light, a pull-up resistor of 1K can cause a current of 5mA!

Moreover, this "larger" current is all poured into the pins of the microcontroller, although it may not burn out, it is also a needless energy consumption.

Judging from this phenomenon, this circuit is not reasonable enough.

If possible, a "sink current" load circuit should be used as much as possible.

Regarding the output drive of the MCU pins, etc., can be seen:

It is not correct to connect it like this, and it is easy to damage the single-chip microcomputer.

A resistor should be inserted in series in the LED circuit, and the resistance should be selected according to the LED parameters, generally 5mA can be used, such as 1K resistor in series.

When the 5V voltage is directly applied to both ends of the diode, the current will be very large, and the diode may be burned out, and even if it is not burned, the voltage difference rule will no longer be observed.

If the parameters of the single-chip microcomputer allow direct driving, the IO port can be connected to a resistor and then connected to the LED to the ground, and the output level is high and the LED is lit at this time.

If the single-chip microcomputer cannot be driven, the voltage positive termination diode can be used and then connected to the resistor to the IO port, and the output level is low and the LED is lit.