LM4780 & K8040 auto stand by function - diyAudio
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Old 9th July 2005, 11:04 AM   #1
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Default LM4780 & K8040 auto stand by function

Hello everybody.

I want to make the stand by function like the K8040 kit of Velleman (TDA7293) (www.velleman.be) but adapted on the LM 4780, and without the PIC12C508A:

Features of the K8040:
-auto-power on possibility when input signal is sensed
-auto-standby function when no input signal is sensed


Is it possible?

the pcb is:
Click the image to open in full size.


Please for a larger view of the DIAGRAM go on page 26 of this pdf: http://www.velleman.be/Downloads/0/Manual_K8040.pdf

To best understand the fonction, please read this MANUAL available here:
http://www.velleman.be/Downloads/0/UserManual_K8040.pdf


To sum up:

I want : no signal => mute pin of the LM4780 oppened or switched to ground
signal >5mVrms =>mute pin of the LM connected to V-

I think a relay can switch the two modes?

It will be interesting for many people because there no problem of motorbording when there is no signal, because the chip is on mute mode.(so no signal in speakers)

Anyone have an idea?

Thanks for answers
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Old 9th July 2005, 03:06 PM   #2
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The LM4780 has a mute pin (actually a pair of mute pins) if you ground the pin the amp mutes. The current drawn by the mute pin is 0.5 ma -- National has the formula for the resistor, and RC combo to set the delay in turning the amplifier on.

You could use the Velleman circuit -- the output of the second LM358 is used to drive the base of a transistor as a relay driver -- just adjust the values of R10 and R11 for your relay. You may also want to play with some of the capacitor values.

Click the image to open in full size.
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Old 10th July 2005, 01:16 PM   #3
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Thanks for schematics.

I place the relay in series with D4?

I did this:

Click the image to open in full size.


I don't know the reference of the diode to protect the 2n2222?

Is this board good?
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Old 10th July 2005, 02:24 PM   #4
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The relays I have on hand had pretty high DCR of 125 ohms, inductance of 60 millihenries -- the current through Q1 is limited by the coil resistance. Your mileage may vary -- check the DCR of the relay and make sure that the transistor is capable of handling it.

I show a snubber on the contact side of the relay -- this will prevent arcing.

Click the image to open in full size.
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Old 10th July 2005, 02:35 PM   #5
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Thanks for details.
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Old 20th July 2005, 05:23 PM   #6
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I did a circuit on a Veroboard. It is very simple and it works very well!!

You can control a relay with a "line-in" signal and so control the device you want: amplifier, pre-amplifier, ....

When you don't listen music during 5minutes, your device(s) shut down automaticaly.

Link:

Site in French: Homecinema-fr.com

Link for the ELEKTOR schema:

ELEKTOR SCHEMA

Everybody can understand the schema even though you don't speak/read french.
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Old 26th July 2005, 08:08 AM   #7
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Hello

I am designing a circuit using PIC, no need for any opamps, the PIC has an ADC, and will do the standby function if no siganl present, when siganl is present, it activates the chip amplifier.

This design is general purpose one, so it can be used with any chip that has a mute or standby functions. Also the PIC has two outputs, the first is active high, and the other is active low, so that it can be used for chips that have active-low standby, and chips that have active-high standby function also.

If any one is interested, send me an e-mail.

Kind day
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Old 26th July 2005, 12:57 PM   #8
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Quote:
Originally posted by metal
Hello

I am designing a circuit using PIC, no need for any opamps, the PIC has an ADC, and will do the standby function if no siganl present, when siganl is present, it activates the chip amplifier.

This design is general purpose one, so it can be used with any chip that has a mute or standby functions. Also the PIC has two outputs, the first is active high, and the other is active low, so that it can be used for chips that have active-low standby, and chips that have active-high standby function also.

If any one is interested, send me an e-mail.

Kind day
Just make sure that the PIC's clock can't couple to the analog lines -- you will probably need an opamp buffer by the way as the PIC ADC input impedance isn't as high as an opamp. You will need to filter the input anyway.
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Old 26th July 2005, 06:54 PM   #9
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Quote:
Just make sure that the PIC's clock can't couple to the analog lines -- you will probably need an opamp buffer by the way as the PIC ADC input impedance isn't as high as an opamp. You will need to filter the input anyway.
There will be no problem with that, the PIC clock is 20 MHz, so, you will never hear it, neither feel it also

The PIC also contains an opamp and no need to filter the input any way.

If any one wants to get a readily programmed PIC and the schematic diagram, send me email on oash82@yahoo.com

Kind day
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Old 23rd March 2007, 01:21 PM   #10
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Quote:
Originally posted by john_lenfr
I did a circuit on a Veroboard. It is very simple and it works very well!!

You can control a relay with a "line-in" signal and so control the device you want: amplifier, pre-amplifier, ....

When you don't listen music during 5minutes, your device(s) shut down automaticaly.

Link:

Site in French: Homecinema-fr.com

Link for the ELEKTOR schema:

ELEKTOR SCHEMA

Everybody can understand the schema even though you don't speak/read french.
I know this is an old topic but, there are two schematics on the link and i plan to make an auto switch to my amp. Which circuit should i apply for it?

Thanks.
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Best regards,
Ozgur
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