Create a schematic diagram of an electric fence controller using the NE556 dual timer IC.
The circuit must include all components with clear electronic symbols (resistors, capacitors, transistors, diode, relay)
connected by lines as in a real circuit diagram.
Specifications:
1. Power supply:
- Vcc = +12V connected to pin 14 of the NE556.
- Pin 1 of the NE556 to ground.
2. Timer A (active 10 seconds):
- Pin 2 (Trigger A) receives a pulse from transistor Q2 (contact detector).
- Pin 6 (Threshold A) connected to Pin 7 (Discharge A).
- R1 = 1 MΩ between Pin 7 and +12V.
- C1 = 10 µF between Pin 6 and ground.
- Pin 3 (Out A) goes through a 4.7 kΩ resistor to the base of Q1 (BC547 NPN transistor).
- Pin 3 also connected via a 100 nF capacitor to Pin 13 (Trigger B of Timer B).
3. Timer B (rest 10 seconds):
- Pin 9 (Discharge B) and Pin 8 (Threshold B) connected together.
- R2 = 1 MΩ between Pin 9 and +12V.
- C2 = 10 µF between Pin 8 and ground.
- Pin 12 (Out B) can be optionally used to block retrigger of Timer A.
4. Relay driver stage:
- Q1 = BC547 NPN transistor.
- Base connected through 4.7 kΩ resistor to Pin 3 (Out A).
- Emitter to ground.
- Collector connected to one side of the relay coil.
- Other side of relay coil connected to +12V.
- A diode 1N4007 placed in parallel with the relay coil (cathode to +12V, anode to collector of Q1).
- Relay contacts switch the +12V supply to the electric fence energizer.
5. Contact detector:
- Shunt resistor ≈0.1 Ω placed in series with the fence output.
- Q2 = BC547 NPN transistor, base connected to the shunt, emitter to ground, collector to Pin 2 (Trigger A).
- When current flows through the shunt, Q2 provides a trigger pulse to Timer A.
Please draw the schematic in a standard style with components connected by straight lines,
not in block diagrams. Show clear pin numbers of the NE556 and all external components.
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