Servo & speaker protection combo

[Wavebourn]

Here is what I am going to use as a servo and speaker protection.

Speaker protection is triggered by clipping of servo, i.e. when there is some voltage greater than 0.3V on it's inverting input. Opamps are TL061

Any comments/suggestions?

 

[AndrewT]

is it really a clipping detector?
or,
is it a window comparator between signal ground and the signal input to the servo opamp?

Why do the two diode cause triggering @ ~300mV?

 

[sivan_and]

...an LED in series with the relay ?...IC 555 will drive the relay directly ..the circuit around the trigger... need lots of modifications to work properly...
"AndrewT " do the two diode cause triggering @ ~300mV?"
suppose he used low drop schotky diodes..

 

[Wavebourn]

Thank you both. I am going to make a PCB, if no suggestions.

 

[Bob Cordell]

Hi Wavebourn,

Great minds think alike. I have used the output of the servo as a trigger for speaker protection for several years. I put a window detector on the output of the integrator and use it to open the speaker relay if the magnitude of attempted correction by the servo is greater than about half the available correction voltage.

Cheers,
Bob

 

[Wavebourn]

Hi Wavebourn,

Great minds think alike. I have used the output of the servo as a trigger for speaker protection for several years. I put a window detector on the output of the integrator and use it to open the speaker relay if the magnitude of attempted correction by the servo is greater than about half the available correction voltage.

Thank you Bob;
I used similar approach before, but now decided to allow servo to try all it's best and to trigger protection as soon as servo can't keep up anymore, and voltage on it's inverting input abruptly changes.
I will probably need 2 more diodes, to protect inputs of opamps from an overvoltage.

 

[AndrewT]

...IC 555 will drive the relay directly ..

24volt relay.
7555 powered from 12V.
How?

 

[sivan_and]

24volt relay.
7555 powered from 12V.
How?

use 12 volt relay (& reduce 24 to 12 relay driving volts)

 

[Wavebourn]

use 12 volt relay (& reduce 24 to 12 relay driving volts)

Unfortunately I have no 15A relays with 12V coil that can be driven by less than 100 mA current; all 15A relays I have need 24V 20 mA.
Couple of advantages are: I can use LED in series with the relay, and I can keep 12V rail, that is used for a servo as well, clean. However, there is one more advantage: industrial control transformers with 18V secondaries I have will fit well in this particular application.

 

[sivan_and]

am afraid your design is for your personal use, and unsuitable for universal use..

 

[Wavebourn]

am afraid your design is for your personal use, and unsuitable for universal use..

Do you mean universal use requires powering of relay from regulated 12V rail that adds requirements to the voltage regulator, and usage of more expensive custom power transformer instead of cheap industrial control transformer?