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Old 10th November 2012, 09:51 AM   #1
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Default uPC1237 too slow

Hi everybody.
I built this circuit up from the datasheet. Works great, except that if I use a fresh 9V battery on the loudspeaker connections to check operation, it switches in to protect, but only after 2 seconds. Is this normal? Should I use a higher voltage perhaps to test( don't wanna damage my speakers)
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Old 10th November 2012, 10:50 AM   #2
Bensen is offline Bensen  Belgium
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This could be normal and depends on you RC combination at the input of your circuit.
For example, I'm using the TA7317 chip for this, for 9V at the input, the response time is 0.2s when using an RC combination of 56k/47F.

What is your RC combination?
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Old 10th November 2012, 03:50 PM   #3
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Quote:
Originally Posted by Bensen View Post
This could be normal and depends on you RC combination at the input of your circuit.
For example, I'm using the TA7317 chip for this, for 9V at the input, the response time is 0.2s when using an RC combination of 56k/47F.

What is your RC combination?
Im using 50uf parallel to 56k fed by 56k from amp output.
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Old 10th November 2012, 05:58 PM   #4
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The 'error voltage' (in your case 9V) is also of importance.
The error voltage charges the C through the R and the time it takes for the C to charge to the switching threshold depends also on the voltage. There is always a delay to avoid switching on too fast with a bass frequency signal. 0.2 secs for 9V doesn't sound too bad to me.

The other thing is the threshold voltage (point where switching occurs) which also is variable and must be set.

Can you post the circuit diagram of your setup?

jan didden
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Last edited by jan.didden; 10th November 2012 at 06:03 PM.
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Old 10th November 2012, 06:02 PM   #5
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Let's put some numbers on it.
Take 10V, 28k (2*56k parallel), 50uF, and a threshold voltage of 1V. With the familiar equation C*dV=I*dT gives T(delay)= C * V/I gives 0.28secs.
So your 0.2secs is faster, probably because your threshold is lower than the 1V in my example.

jan
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Old 12th November 2012, 05:19 AM   #6
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Mine is 2 seconds. Not 0,2 secs.
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Old 12th November 2012, 04:48 PM   #7
Bensen is offline Bensen  Belgium
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Quote:
Originally Posted by diy didi View Post
Im using 50uf parallel to 56k fed by 56k from amp output.
Could you remove the 56K // with the 50 cap. This should give a much faster response.
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Old 12th November 2012, 06:46 PM   #8
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will give it a try
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Old 12th December 2012, 06:02 AM   #9
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Quote:
Originally Posted by diy didi View Post
will give it a try
Had same prob. with NEC UPC1237 ref. design (330uf with 56K ). I made the combination 10uf with 56K. Didn't had a single false trigger with any bass heavy music, works like a charm.
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