12V DC Speaker Protector Circuit

Introduction: 

A speaker protector circuit is a crucial component in audio systems, designed to protect speakers from damage caused by current surges, DC voltage, and other disturbances. This article will discuss the 12V DC speaker protector circuit scheme shown in the image.

Pcb Layout

Component List:

1. 12V DC Relay
2. Capacitors: 47/50V and 100/50V
3. 22uF Capacitors (2 pieces)
4. Resistors: 560Ω (2 pieces), 22kΩ (2 pieces), 390kΩ, 47kΩ
5. 4148 Diodes (5 pieces)
6. 4007 Diodes (2 pieces)
7. LEDs (2 pieces)
8. BC547 Transistors (2 pieces)
9. BC557 Transistor
10. DZ6.2V Zener Diode
11. Audio input and output terminals

Circuit Operation:

1. When powered on, the relay doesn't activate immediately, preventing current surges to the speakers.
2. The RC (resistor-capacitor) circuit creates a delay to stabilize the voltage.
3. Transistors and zener diode function as comparators, detecting unwanted DC voltage.
4. Under normal conditions, the relay activates and connects the audio input to the output.
5. LEDs light up as indicators that the circuit is working and speakers are connected.
6. If DC voltage or disturbances are detected, the relay will disconnect the speakers.

Assembly:

1. Mount components on the 50 x 85mm PCB according to the schematic.
2. Ensure correct orientation of components like diodes, transistors, and capacitors.
3. Carefully solder all components.
4. Check connections to avoid short circuits.
5. Install audio input and output terminals.

Advantages:

1. Protects speakers from current surges and DC voltage.
2. Prevents "pop" sounds when the system is turned on or off.
3. LED indicators allow easy monitoring of circuit status.
4. Compact design (50 x 85mm) facilitates integration into audio systems.
5. Uses readily available and affordable components.

Limitations:

1. Only works with 12V DC systems.
2. Slight delay when turning on the audio system.
3. Does not protect against all types of audio disturbances.
4. Requires a separate 12V power source.

Conclusion: 

This 12V DC speaker protector circuit is an effective solution for protecting speakers in audio systems. Although it has some limitations, the protective benefits it provides are significant. Implementing this circuit can enhance the reliability and lifespan of audio systems, particularly for car applications or portable audio systems using 12V DC power sources.

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Soft Start Circuit for Amplifiers - PCB Layout

 Introduction: A soft start circuit is a crucial component in amplifier systems, designed to reduce inrush current when the amplifier is powered on. This circuit helps protect amplifier components and extends their lifespan. This article will discuss the 47R/20W soft start circuit scheme shown in the image.

Component List:

1. 47R/20W Resistor
2. Songle SLA-12VDC-SL-C 30A Relay
3. 220uF/25V Capacitor
4. 330 ohm/400V Resistors (2 pieces)
5. 10K Resistor
6. 1N4007 Diodes (4 pieces)
7. Fuse
8. Led
9. Input and output terminals

Circuit Operation:

1. When the amplifier is turned on, current flows through the 47R/20W resistor, limiting initial current.
2. The 220uF/25V capacitor begins to charge, creating a delay.
3. After a few seconds, the voltage across the capacitor is sufficient to activate the relay.
4. The relay closes, bypassing the 47R/20W resistor and directly connecting input to output.
5. The amplifier now operates at full power.

Assembly:

1. Mount components on the PCB according to the schematic.
2. Ensure correct orientation of components like the relay and capacitor.
3. Carefully solder all components.
4. Check connections to avoid short circuits.
5. Install the fuse in the designated location.

Advantages:

1. Protects the amplifier from inrush current when powered on.
2. Extends the lifespan of amplifier components.
3. Reduces the risk of damage to speakers.
4. Simple design and easy to implement.

Limitations:

1. Slight delay when turning on the amplifier.
2. Additional components increase production costs.
3. Requires extra space in the amplifier casing.

Conclusion: 

The 47R/20W soft start circuit is an effective solution for protecting amplifiers from inrush current at power-on. Although there is a slight delay and additional cost, the protective benefits far outweigh these drawbacks. Implementing this circuit can significantly improve the reliability and lifespan of amplifier systems.

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TDA7293 Stereo Amplifier: 2x 100W Configuration with PCB Design

 

Introducing a high-quality audio solution: a stereo amplifier using the TDA7293 IC, capable of producing output up to 2x 100 Watts. This article will discuss the circuit diagram along with the recommended PCB design.

Key Features:

1. Integrated power supply - only requires an external transformer
2. Compact single-sided PCB design
3. Superior sound quality
4. Versatile for various audio applications

Safety Features:

• Mute/stand-by circuit to avoid 'clicks' during power on/off
• No output relay required

Transformer Recommendations:

• Range: 18-0-18V to 33-0-33V
• Power: 200VA
• Note: Lower voltage may require less current

PCB LAYOUT

Part	Value	Description	Quantitity
Capasitors
C1, C4, C8, C13, C16, C20	100nF/100v	Ceramic Capacitor	6
C2, C23	1µF/63V	Polyester Capacitor	2
C3, C5, C6, C17	22µF/63V	Electrolytic capacitor	4
C7, C19	47µF/63V	Electrolytic capacitor	2
C9, C11	10.000µF/63V	Electrolytic capacitor	2
C21, C22	220p/100V	Ceramic Capacitor	2
Semiconductors
D1	1N4148	Diode	1
IC1	TDA7293, TDA7294 or TDa7295, or TDA7296	Audio amplifier integrated circuit	2
B1	GBJ3510, GBJ2510 or equivalent	Bridge rectifier	1
LED1, LED2	Led 5MM	Red LED or color of your choice	2
Resistors
R1, R2, R7R10, R11	22K	Red, red, orange, gold	4
R3, R13	680	Blue, gray, brown, gold	2
R4	33k	Orange, orange, orange, gold	1
R5	10k	Brown, black, orange, gold	1
R6, R12	2,7 ohm 1 Watt	Red, violet, gold, gold	2
R8, R9	4,7K	Yellow, violet, red, gold	2
R14, R15	1,8K	Brown, black, red, gold	2
Miscellaneous
CN1	LIN	Jst Xh 2-Way Connector 2.54 mm pitch or equivalent	1
CN2	RIN	Jst Xh 2-Way Connector 2.54 mm pitch or equivalent	1
CN3	AC	Terminal block 3 pin 5.08 mm	1
CN4	OUTL	Terminal block 2 pin 5.08 mm	1
CN5	OUTR	Terminal block 2 pin 5.08 mm	1

 

Assembly Warning: Insulate the IC body from the heatsink using a mica or plastic thermal pad.

Circuit Analysis:

1. High-Pass Filter (C2, C23, R1, R10):
   • Influences low frequencies
   • Cut-off frequency varies based on capacitor value: 470nF: ~15Hz 1μF: ~7Hz 2.2μF: ~3.2Hz
   • Formula: f = 1/(2ΠRC)
2. Low-Pass Filter (R15/C21, R4/C22):
   • Prevents high-frequency signals
   • Default cut-off: ~400 KHz
   • Adjustable by changing component values
   • Formula same as high-pass filter
3. Mute Circuit (C5, C6, R5, R7):
   • Reduces 'pop' during power on/off
   • Sets switching time constant
4. Gain Settings (R11-R13, R2-R3):
   • Default configuration: 30 dB
   • Can be modified (ensure R11-R2 = R13-R3)
5. Input Impedance: Determined by R1-R10
6. Zobel Network (R6-C4, R12-C16):
   • Prevents oscillation from speaker wire parasitic induction
   • Filters radio interference
7. Additional Capacitors:
   • C7, C19: DC decoupling of feedback
   • C3, C17: Bootstrapping (different position for TDA7293)

By understanding each section of this circuit, you can optimize the amplifier's performance according to your specific audio project requirements.

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