Rendering demonstration of triode switching delay circuit_Basic hardware circuit diagram explanation

Circuit diagram:

Circuit function analysis:

In this example, a triode is used to form a delay control circuit to control the action of the relay. When the button is pressed, the relay operates, and after a delay, the relay releases.

Circuit breakdown:

This circuit can be divided into two parts:

One is a delay circuit composed of a conforming tube composed of transistors Q1 and Q2 and peripheral resistors and capacitors;

The second is a switching circuit composed of transistor Q3 and relay.

Circuit working process:

1. When the circuit is powered on and the tact switch S1 is not pressed, the power supply charges the capacitor C1 through the resistor R2, and the charging process is very fast. The voltage charged on capacitor C1 is the power supply voltage.

2. When the tactile switch S1 is pressed, the power passes through the switch S1, and the resistor R1 is added to the base of the transistor Q1. The base of Q1 obtains a bias current, causing the transistor Q1 to conduct. At the same time, the base of Q2 also obtains a bias current, causing Q2 to also conduction. At the same time, capacitor C1 passes through diode D1 and switch S1 is quickly discharged.

3. After Q2 is turned on, the collector voltage of Q2 is close to 0V.

4. The collector voltage of transistor Q2 is low level, causing the base of transistor Q3 to be low level. Q3 is a PNP transistor, so Q3 starts to conduct, current flows in the relay coil, and the normally open contact of the relay closes and emits light. Diode D3 is lit.

5. After the light switch S1 is released, the transistors Q1 and Q2 are cut off, and the capacitor C1 begins to charge. The charging voltage becomes negative on the left and positive on the right, causing the base voltage of the transistor Q3 to slowly rise. During the charging process of capacitor C1, transistor Q3 can maintain conduction for a period of time, causing light-emitting diode D3 to gradually extinguish.

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Circuit diagram:

Circuit diagram functions:

This example circuit can be used for functional testing of the optocoupler, and can also be used for debugging of a certain optocoupler.

Circuit diagram explanation:

In the circuit diagram, switch S1 is the power switch and S2 is the test switch.

Resistors RP and R1 are the current limiting resistors at the input end of the photocoupler, R2 is the pull-up resistor at the output end, and the LED is the output indicator.

When connecting the optocoupler, turn on the power switch S1 and hold down the switch S2 at the same time. If the output LED emits light and the brightness of the LED can be changed by adjusting RP, it means that the LED is functioning normally.

This is a functional test. If an optocoupler needs to be debugged, this method can also be used to record the input resistance and output resistance when the LED emits the brightest brightness. Of course, at this time, the output pull-up resistor R2 can also be replaced by an adjustable resistor.

Notice:

The test circuit here is limited to SOP-4 packaging, and the pin definition of the chip must be consistent with the optocoupler in the circuit diagram.

-The Electronic Components Purchasing Network (www, oneyac, com) is a local component catalog distributor. It adopts the "small batch, spot, sample" sales model and is committed to meeting customers' procurement needs for multiple models, high quality, and fast delivery. Self-built and efficient intelligent warehousing, with over 50,000 self-operated inventories, provides one-stop genuine spot procurement, personalized solutions, option substitution and other diversified services. (This article is compiled from the Internet for the purpose of disseminating useful information and knowledge. If there is any infringement, please contact the administrator to delete it)