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

Click For Summary
SUMMARY

The discussion centers on the connection of an NPN transistor (BC547) in an automatic school bell circuit utilizing a 555 timer. The outputs from pins 3 to 11 are linked to the transistor's base through a 1K resistor, with diodes ensuring only one output activates the transistor. The transistor is positioned between pin 7 and the junction of pins 6 and 2, with a 10K resistor connecting pin 7 to a 12V source. The user questions whether the emitter should connect to pin 7 instead of the collector to ensure proper discharge functionality in astable mode, indicating a practical failure of their initial design.

PREREQUISITES
  • Understanding of 555 timer operation in astable mode
  • Knowledge of NPN transistor characteristics and configurations
  • Familiarity with basic electronic components such as resistors and diodes
  • Experience with circuit design and troubleshooting techniques
NEXT STEPS
  • Study the operation of the 555 timer in astable mode
  • Learn about NPN transistor configurations and their applications
  • Research common issues in transistor-based circuit designs
  • Explore practical examples of automatic bell circuits using 555 timers
USEFUL FOR

Electronics enthusiasts, circuit designers, and students working on projects involving 555 timers and transistor applications will benefit from this discussion.

titangsu
Messages
5
Reaction score
0
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.
 
Engineering news on Phys.org

Similar threads

Will the bleed resistors enable a shorter path to ground or not?
  • · Replies 80 ·
3
Replies
80
Views
5K
I tried building an induction coil
  • · Replies 34 ·
2
Replies
34
Views
3K
Transistor connection in the discharge path of the 555 timer
  • · Replies 1 ·
Replies
1
Views
2K
Powering a 555 Timer Circuit with 9VDC Battery
  • · Replies 9 ·
Replies
9
Views
2K
Is there a way to keep an LED turned on even when the power source is off?
  • · Replies 2 ·
Replies
2
Views
2K
Build a Lightning Cloud with a 555 Timer | LED Flashing Help
  • · Replies 16 ·
Replies
16
Views
3K
Troubleshooting Transistor Switching with Arduino
  • · Replies 7 ·
Replies
7
Views
4K
Solve NPN Transistor Puzzle: -0.4V?
  • · Replies 5 ·
Replies
5
Views
2K
Need help with confirming if this 555 timer circuit with transistor will work?
  • · Replies 2 ·
Replies
2
Views
6K
How does a simple oscillator work in non-ideal conditions?
  • · Replies 30 ·
2
Replies
30
Views
6K