Amplifiers and Loudspeakers Protector with IC LM393

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The short circuit proof
outputs of amplifiers and speakers, throw some interesting elements,
such as the isolation of the speakers from the exit of the amplifier,
when is a constant tension presented abandoned or if the heat sink
temperature rises excessively, the simultaneous and delayed connecting
speakers to the amplifier so until we stop them, the familiar sounds of
the charge – discharge of capacitors of the supply.

Circuit

Circuit diagram

It is formed by a binary comparator [IC 1], the transistors Q1-2 and preliminary LED
D5-6. The supply of the circuit can have a positive stress [point A],
especially the food that is on the D3 and R17, the 15V + stabilized.
Point B is one of the secondary coil of the main AC-connected
transformer. When the power switch of the AC main line, then an AC
voltage (secondary coil of the transformer), is shown in section B, is
it? D2 from the negative voltage is recovered and deliver them by R9,
cut the Q3 of this year and start charging the C4-R10-11.

As long as the last time that the charge on the capacitor, the input
[+] IC2B comparator is found in small amounts in proportion to the
power [-]. The output of IC2B has a low level, so Q4 will remain in the
Cutt off and stay ahead of the RL1, which he D6. Only the C4 is charged,
the situation changes in the IC1B, RL1 is activated, the speakers to
the output of the amplifier, the D6 it out. If it’s interrupted, the
process is reversed, and the speaker without breaking pass interference.

If the circuit during the work, the problem of continuing tensions
in the output of the amplifier presented in the RL1 and protects the
speaker. This is done using the Q1-2. The acoustic signal from the
amplifier output, led to point D, the alternative tensions led to the
bottom of the C1-2, which is a non-polar capacitor. Continuous voltage
that is greater or less than 1.7 V ? 4.8V, immediately activates the Q1 or Q2 of each. With the activation of the transistors of the input level decreases [] by IC1B, so turn off and RL1.

Part List

R1-2=27 Kohms
R3=1.4 Kohms
R4=1 Mohms
R5-14-17=3.3 Kohms
R6-7=100 Kohms
R8=47 Kohms
R9-11=120 Kohms
R10=470 Kohms
R12=15 Kohms
R13=1.5 Kohms
R15=4.7 Kohms
R16=33 Kohms
R18=1.5 Kohms 5W
C1-2=100uF 63V
C3=470nF 100V MKT
C4-5=47uF 25V
Q1-2-3=BC337
Q4=BC639
D1=1N4148
D2=1N4004
D3=15V 1.5W Zener
D4=1N4002
D5-6=LED
RL1=24V Relay
RTH=KTY81-122
IC1=LM393