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Old 18th May 2010, 01:21 PM   #11
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Post Current sense

A current sense circuit, Included in the amplifier section. that Triggers the Protection circuit, to disconnect the loudspeaker for two seconds.
Warning the user of the low load.


In my case I can adjust it to disconnect the speaker for 2 seconds or 3 seconds. at

4 ohms
OR
2 ohms



Thanks
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Old 18th May 2010, 01:23 PM   #12
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in small PA setup with two or three amps ...this is never supposed to happen then again the stress you are going to produce in relays psu and clamp diodes with a quick click at full power is way too much trouble and it can create more drouble than it can solve


What i meant also in my previous post everybody things that the amplifier is untouchable and everything you do happens after the amplifier ....the idea and solutions needed BEFORE OR MUCH BEFORE the relay clicks or the vi limmiter has been eating all your sonics
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Last edited by east electronics; 18th May 2010 at 01:26 PM.
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Old 18th May 2010, 02:06 PM   #13
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i have a idea in mind ...... How bout putting a sensing resistance in series with the load may be (0.1E) then take two connections from the end of the resistor and feed it to a differential amp and then feed the o/p of the diif amp to a comparator which in turn drives a relay .......
As soon as a high current pass through the sensing resistor a voltage drop will be there which will amplified using the diff amp then the diff amp will drive the comparator and and the comparator will activate a relay which will disconnect the load and the amp will be protected....... Suggestions if this concept will work ......

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aniket
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Old 18th May 2010, 04:15 PM   #14
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Default protection circuit

here is protection scheme I think will work wat do u think ?????????

circuit>>>>>>>>>>>











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Aniket
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Old 18th May 2010, 04:49 PM   #15
Mooly is offline Mooly  United Kingdom
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I can see what you are thinking but I'm afraid it won't work.

You are showing the speaker across the 12 volt supply.

You can sense current using a low value resistor (but you need to be able to sense both polarities... an amp can fail either way.
Sensing like this relies on a large current in the sense resistor (up to the max output of the amp) before the circuit trips... and there is no integrating of the audio either... the slightest peak over the set level would activate it.
For DC offset it's no good as the current to trip it is as stated way to high... the speaker would be toast

Good thinking though
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Old 18th May 2010, 08:18 PM   #16
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ok my bad here is the corrected schematic ... I already have a dc detect protection circuit from rangy slones book & a turn on delay ............ I also have a temperature based fan speed regulator from rod elliot ..... Neways the sensing resistor is in series with load so why should nt detect the negative part of the signal...... Correct me if I am wrong

circuit






regards
aniket
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Old 18th May 2010, 09:08 PM   #17
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Hi Phoenix,

Your idea could work with a bit of refinement. Firstly you do not want to reference your circuit to the amplifier ground, it should be "floating" like your Multi meter. Secondly you may want to add a full wave bridge so that you can monitor negative and positive faults, and thirdly you may want to add an integrator as Mooly suggests so that you don't cut the speakers for any peak, but only those that say lasts for more than 1 second.

Finally I do not think it should reset automatically but should latch so that you need user intervention to check what went wrong and maybe have to turn the amp on and off for it to reset.

On the whole this is not a bad idea for protecting your speakers for fault currents which is the most damaging to speakers.

I guess some of the purists would argue that you are messing with the damping factor by incorporating a series resistance, but for a protection circuit this is a fine idea. Try refining your idea and post it as a complete add on board, I am sure there are many here that could make use of it.

Kind regards

Nico
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Old 18th May 2010, 09:38 PM   #18
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can u show me how to do wat u suggested ................ i will be trying it on my own a bit of suggestion would be very help full .....................


regards
aniket
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Old 19th May 2010, 12:55 AM   #19
dangus is offline dangus  Canada
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Here's the schematic of an "AF Drive Indicator" that was published in Elektor in the early '90s. The article includes a PC board layout. LEDs indicate clipping and 3 dB below clipping.
AF Drive Indicator Schematic
If anyone is interested, let me know and I'll scan the original article.
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Old 19th May 2010, 01:00 AM   #20
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Quote:
Originally Posted by dangus View Post
Here's the schematic of an "AF Drive Indicator" that was published in Elektor in the early '90s. The article includes a PC board layout. LEDs indicate clipping and 3 dB below clipping.
AF Drive Indicator Schematic
If anyone is interested, let me know and I'll scan the original article.
Wow thats a lot of components.

I can do a clip led with 5 small cheap components including the LED !
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