UPC1237 + LM3915 as power limiter ....

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emilvv

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Joined 2008
#1
Hello,

I want to combine UPC1237 with LM3915 ....

The goal is when LM3915 detects ( in point mode ) critical level of power .. from one of its output pins to pass this signal to pin 1 of UPC1237 .... UPC1237 disconnects the speaker and after 3-4 seconds connects it again .. ( that is mode for UPC1237 .. )

Please, see 'my' schematic and if it is possible correct values of incorrect Resistors .... or anything else ....

Also if it is not good idea ... please tell me why it is not .... 🙂

I have this ICs so please don't offer me another decisions ...

Thank you in advance,

Emil
 

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#2
This solution is hard to use as limiter. Turning OFF the output relay is very hard action. It will be frustrating in daily use, and can reduce the lifetime of the relay.
If You want to use LM3915, just add LDR, driven by the peak LED.

Sajti
 
#4
Hi Emil,
You are switching the relay at the worst possible time. You will bake the contacts in very short order.

Why not trip a signal relay to short the input instead? You achieve the same result, but with a long lasting setup. Otherwise your project seems to be well thought out, and it will work this way.

-Chris
 
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#5
emilvv said:
.......If output power is near to tweeter max power ... then the relay will be OFF.....If power is about and low speakers power limit .. the relay is NOT in use ...
Click to expand...
And what if the signal only briefly but repeatedly exceeds the tweeter rating, as normally occurs with music? This can be quite safe and normal with most speaker drivers. The relay though, would open frequently when there was really no need to.

The next issue is how you distinguish between bass and treble in the manner of the crossover network. Some music has very little HF content and other forms have much more, so the correlation between average power and peak treble power will vary a lot between the various recordings in play.

It might seem like a good protection scheme in principle but you need to consider how your circuits will operate with real audio, where high peak currents with low average current are normal. Extreme peak currents may pass through speakers without damage but sustained tones, though lower energy, are what cause speaker coils to overheat and burn.

A good protection system will integrate power and duration of the signal peaks to control the exposure of the speakers to overload. Sometimes, a simple means of doing that may just be a thermal-magnetic circuit breaker.
 
#6
There isn't a perfect protection circuit for tweeters in common use. What kills most tweeters are clipped musical waveforms, although feedback through a microphone is also a very effective tweeter killer.

So, where where you sensing the power? At the tweeter output of the crossover, or the amplifier output terminals? Your sense point will dictate how your protection network operates, and the UPC1237 would work alone. The meter chip can then simply give you a visual indication of power level, both parts are simply used as intended in other words.

-Chris
 
#7
A2

Hello,

Thank you for answers !!

Let me add some more details ....

I am planning to make multi channel system.... so..

Audio signal --> ADAU1701 DSP --> BASS + MID + TWEETER signals --> 3 x QUAD 909 --> Subwoofer + Mid speaker + Tweeter ...

Or simply for tweeters ..

ADAU1701 --> audio signal --> quad 909 ( 50-100 W ) --> HP capacitor filter --> 30W tweeter...

... work mode of UPC1237 is with delay in example 4-5 secs ..

Example work ...

In test setup will see where is the desired limiter LED, flashing on 20 W high freq signals ...... or when i feel it is danger level .. by my hearing ... 🙂 So will connect it to Pin 1 of UPC1237 ..

If peak signal with high freq is appearing ..... LM3915 will shutdown ucp1237 for new 4-5seconds ( first was starting delay ... ) and I have lower the volume or stop the music ... 🙂

My question is mainly for the schematic is it with correct R values - hwat you mean ...???

I will try to make test setup and to see haw it will work ...

Regards,

Emil
 
#10
Hi Emil,
Okay, so you're going to run the tweeter off it's own amplifier. In that case, you don't need to use the LM3915 at all. The uPC1237 could do it all. What the LM3915 could give you is an adjustable warning level and then trip the uPC1237. If you used an R-C network between the LM3915 and the uPC1237, you could allow for peaks simply through the time delay you could set there. The relay should still short the input of the tweeter amplifier so you can use it for years. Shorting or opening the amplifier output would be the last option. Just kill the input signal.

Since you are using an active crossover, your method should work great. Good thinking!

-Chris
 
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