Rendering demonstration of a 4-way answering machine made using op amp_Basic hardware circuit diagram explanation

Answerer circuit diagram:

Circuit function:

Achieve 4-way answering and ensure the uniqueness of successful answering by pressing the button first.

Circuit breakdown:

The circuit in this example can be divided into two main parts:

One is a comparator circuit composed of LM324, with 4 channels;

The second is a locking circuit composed of transistor Q1 and capacitor C1, which blocks other answering buttons after the answering is successful.

The working process of the entire circuit:

When the circuit is powered on, LED D4 is lit as a power indicator light.

When switch S1 is closed, the answering machine working indicator light D3 is lit. At the same time, after being divided by the potentiometer R7, a certain comparison reference voltage is provided to the inverting input terminal of LM324. The non-inverting terminal passes through resistors R3, R5, R6, R8, resistor R9 and the emitter junction of the transistor to the ground, making the non-inverting terminal of the comparator low level, so at this time the comparator output is low level, which is equal to the comparator output. The connected LEDs are all off.

After the answering starts, the LED corresponding to the button pressed first will light up. The principle is as follows:

If S3 is pressed first, resistor R1 and resistor R5 divide the voltage so that pin 5 of the comparator generates a certain voltage (but at this time, due to the effect of capacitor C1, transistor Q1 will not turn on immediately), and this voltage is higher than The voltage at the inverting terminal is high, so the comparator outputs a high level, the light-emitting diode D5 is lit, and is fed back to the non-inverting terminal at the same time, forming a self-locking effect. On the one hand, D5 is always lit, and on the other hand, it also provides base current to transistor Q1 through resistor R5.

After the delay effect of capacitor C1 ends, transistor Q1 is turned on, so that even if other buttons are pressed again, the corresponding comparator non-inverting input terminal will not have a higher voltage and will not output a high level, thus ensuring the answering machine. The uniqueness of success.

Open and then close S1 again to reset the answering circuit before the second round of answering can be carried out.

Notice:

The capacitance value of capacitor C1 in this example is critical, it cannot be too large or too small. When debugging, adjust from large to small. Moreover, this circuit has a bug and does not have a reset function. After answering, it can only be reset by cutting off the power supply, which is not practical. You can modify the circuit to solve this bug. It should also be noted that the power supply of LM324 must be connected from behind switch S1 and cannot be connected to the 12V power supply in front of switch S1.

-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)

Light controlled delay switch circuit diagram:

Circuit function introduction:

The working principle of the circuit in this example is very similar to the previous circuit: light-controlled switch LED, but the logic state in the circuit is different. In this example, a photoresistor is used to realize that when there is light irradiation, the switch is turned on and the LED is lit; when the light irradiation stops, the LED goes out after a delay.

Circuit working process:

1. After the circuit is powered on, when the ambient light is very weak, the photoresistor RG shows a large resistance state, and the transistor Q1 is cut off. Then the emitter of Q1 and the base of Q2 are both 0V, so the transistor Q2 is also cut off, and the relay If there is no action, the LED will not display.

2. When light shines on the photoresistor, the photoresistor RG shows low resistance, the transistor Q1 is turned on, the power supply starts to charge the capacitor C1 through the transistor Q1, and the base voltage of the transistor Q2 begins to rise. When the base voltage of transistor Q2 rises to 0.7V, transistor Q2 begins to conduct, but the current flowing through transistor Q2 is still small at this time, which is not enough to cause the relay to operate; but as the charging voltage of capacitor C1 gradually rises, the current flowing through transistor Q2 gradually rises. The current flowing through transistor Q2 is also getting larger and larger, causing the relay to operate, the normally open contact is closed, and the light-emitting diode D1 is lit.

3. When the light on the photoresistor stops, the photoresistor RG returns to the high resistance state, and the transistor Q1 is turned off; the transistor Q2 can maintain conduction for a period of time during the discharge of the capacitor C1. When the voltage on the capacitor C1 is not enough to turn on the transistor Q2, the relay is disconnected, the normally open contact pops open, and the light-emitting diode D1 goes out.

explain:

1. When capacitor C1 is charging, there is no resistance in the charging circuit, so the entire charging process is very short;

2. The discharge time constant of capacitor C1 is determined by the product of resistor R1 and capacitor C1.

-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)