Connection of the transistor in the discharge path betn 7 & 6 of 555

In summary, the conversation discusses an automatic school bell circuit and the connection of a transistor and diodes to control the output. It is mentioned that there may be an error in the transistor connection which could prevent the circuit from working properly. The speaker seeks assistance in identifying and solving the problem.
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titangsu
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In an automatic school bell circuit, The outputs from 3 to 11 are connected to the base of an NPN (BC547) transistor through 1K resistance. A diode is connected in forward bias in each of those outputs so that only one output sends high pulse to the base of the transistor. When the high pulse is activating the transistor and makes it On it gives the discharging path of the 555 timer. The transistor is connected in between pin 7 and the shorted node of 6 & 2. There are two resistances in series with the emitter and the collector is connected directly to pin 7. Pin 7 is connected to 12V source through 10K resistance. I think the transistor connection will be reverse i.e. emitter will be connected to 7 instead of the collector. Otherwise the transistor will not make the discharge path when the 555 timer is in astable mode.Am I write? But practically my idea does not work. What is the problem? pls help.
 
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1. How does the connection of the transistor between pins 7 and 6 affect the 555 timer?

The connection of the transistor between pins 7 and 6 in the 555 timer affects the discharge path of the timer. This means that when the output is in its low state, the transistor allows the capacitor connected to pin 7 to discharge through pin 6, thus resetting the timer.

2. What type of transistor should be used for this connection?

The type of transistor used for this connection should be a general-purpose NPN transistor. Examples of suitable transistors include 2N3904, 2N2222, and BC547.

3. What is the purpose of this connection in the 555 timer?

The purpose of this connection is to allow for a variable discharge time in the 555 timer. By using the transistor, the discharge path can be controlled and varied, allowing for different timing intervals to be achieved.

4. Can this connection be used to control the output frequency of the 555 timer?

Yes, this connection can be used to control the output frequency of the 555 timer. By varying the discharge time, the overall timing period of the timer can be adjusted, thus affecting the frequency of the output signal.

5. Are there any alternative methods to control the discharge path of the 555 timer?

Yes, there are alternative methods to control the discharge path of the 555 timer. These include using a diode or a resistor in place of the transistor. However, the transistor offers more precise control and is commonly used in circuits involving the 555 timer.

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