Does anyone have a schematic for a switch or relay that is activated by an incoming audio signal? I want to keep my monitors on standby when there is no signal for a preset time but have them switch on when a source reappears. I think there is something like this in those Mackie monitors.
Signal activated switch/relay
- Thread starter mnats
- Start date
Help Support GroupDIY Audio Forum:
Wouldn't it be better to switch their power via a passive-infrared detector like the ones you use in outdoor-lightning? So the speakers will turn on whenever there was someone in the room, and turn off ten minutes after they left?
Jakob E.
Jakob E.
..off course you'll need a PIR detector in your kitchen as well..
:razz:
Jakob E.
:razz:
Jakob E.
sismofyt
Well-known member
Some/most amps need time to stabilise. I wouldn't do it. Besides, they're proably very low bias designs so powerconsumption & heat shouldn't be a prob... I do think I have a schematic.. somewhere.. I could scan. Not sure, I'll look..
But you can have a mighty lotta fun with PIRs :green:
:grin:
But you can have a mighty lotta fun with PIRs :green:
:grin:[quote author="gyraf"]..off course you'll need a PIR detector in your kitchen as well..[/quote]
That will work until the CD finishes and I'm still in the kitchen a hour later. Meanwhile the powered monitors are still running. Hey, maybe I can figure out a way to cook on top of the heatsinks! I could run the tweeter amps class A!
Guess I'll have to design it myself if no one's got a schematic handy.
That will work until the CD finishes and I'm still in the kitchen a hour later. Meanwhile the powered monitors are still running. Hey, maybe I can figure out a way to cook on top of the heatsinks! I could run the tweeter amps class A!
Guess I'll have to design it myself if no one's got a schematic handy.
Mark Burnley
Well-known member
mnats,
One of these might do you....
You'd have to put some sort of hysterisis/delay into the circuit- otherwise the circuit may switch off during quiet passages of music or between tracks!
FWIW, I'd just use a bunch of CMOS gates- take L+R sum (just in case for some weird reason a track has a low left or right hand level- some 60's tracks for example begin with an acoustic guitar in one side only for the first minute or so...crazy panning :shock: ) and take it to an op-amp. This will sum and buffer the audio input. Then take this signal (you may need to amplify it at this op-amp) and feed it into a schmitt trigger (4000 series CMOS- can't remember number!) This will square up the audio signal into a digital signal. Then use a "charge pump" diode/capacitor/resistor network to integrate this rapidly-changing digital signal to a DC level (you may need to clamp it with a diode connected to +5v etc). This can then be buffered and used to drive a 4047 or 555 monostable driving a transistor/relay.
You want the monostable to be "on when activated" for about 30s or so. So when an audio signal arrives at the unit, the output switches "on". But, because audio is still present after 30s, it remains activated. It will keep resetting (the relay won't close inbetween these 30s windows because the monostable resets so quickly, that the relay won't even have time to de-energise because of its sluggish magnetic "memory")
I haven't tested this- I just made it up now if I was going to do it myself :wink:
Some of those links above look good- a lot of the kits have a downloadable pdf with schematic too!
Hope you sort something,
Mark
One of these might do you....
You'd have to put some sort of hysterisis/delay into the circuit- otherwise the circuit may switch off during quiet passages of music or between tracks!
FWIW, I'd just use a bunch of CMOS gates- take L+R sum (just in case for some weird reason a track has a low left or right hand level- some 60's tracks for example begin with an acoustic guitar in one side only for the first minute or so...crazy panning :shock: ) and take it to an op-amp. This will sum and buffer the audio input. Then take this signal (you may need to amplify it at this op-amp) and feed it into a schmitt trigger (4000 series CMOS- can't remember number!) This will square up the audio signal into a digital signal. Then use a "charge pump" diode/capacitor/resistor network to integrate this rapidly-changing digital signal to a DC level (you may need to clamp it with a diode connected to +5v etc). This can then be buffered and used to drive a 4047 or 555 monostable driving a transistor/relay.
You want the monostable to be "on when activated" for about 30s or so. So when an audio signal arrives at the unit, the output switches "on". But, because audio is still present after 30s, it remains activated. It will keep resetting (the relay won't close inbetween these 30s windows because the monostable resets so quickly, that the relay won't even have time to de-energise because of its sluggish magnetic "memory")
I haven't tested this- I just made it up now if I was going to do it myself :wink:
Some of those links above look good- a lot of the kits have a downloadable pdf with schematic too!
Hope you sort something,
Mark
Thanks - I did do a search before posting and came up with some adaptable ideas but nothing specific to the task.
I like your idea and the sound of the word CMOS as the circuit will have to idle waiting for a signal and will probably need a small battery to power it.
I like your idea and the sound of the word CMOS as the circuit will have to idle waiting for a signal and will probably need a small battery to power it.
sismofyt
Well-known member
I have found a schematic. It's an old Elektor schematic. A single LM324 quad some diodes, resistors, caps and a relay. 1-10 min delay time. It's german but very easy to understand, only a single page. DO you want me to scan it for you? Could do it in a few days..
sismofyt
Well-known member
There ain't much text, but we got plenty of germans here :wink: Ohh, wait, I can do german too :green: I'll get it sorted out then..
sismofyt was kind enough to send me some scans of the circuit and the article auf deutsch
Here's the circuit which I redrew:
I typed the text into altavista babelfish and it came out like this:
That does not occur at all so rarely: In the evening before the sleeping going still fast a plate presented and in the morning when waking up stated that the plant "laeuft" still;. That means: Eight (or more) hours unnecessary energy consumption. If the record player does not switch off automatically, then it is added still making more difficult that soon a new needle will be due. In order to make for all mark with the verschwendung a conclusion, Elektor a circuit developed, which does not fall also the sleepiest rear-Fi enthusiast into all too large expenses. With the help of this circuit the plant is switched off automatically after approximately 5 minutes break. How does such function a wonderful energy saver? The input signal comes from the exit of the preamplifier. It is strongly strengthened first of A1 and a2 and reached in this way some volt. With P1 one can stop the reinforcement between 47mal and 4700mal. The sensitivity of the circuit is thus in a large range adjustable. The joke of the circuit consists now of the fact that the plant is already switched off nich at longer music or sprechpausen. In addition still somewhat more than only the stage with A1/A2 is necessary. A3 serves as buffer/amplifier. Its output signal is "umgesetzt" by D1 parallelly and by C6 into DC voltage of the average value of the entrance alternating voltage;. If the tension lies over C6 above a certain value, then the exit of the Schmitt trigger A4 is "high", the relay tightens. If the tension sinks over C6, then the Schmitt trigger switches dei a certain value to "low", and the relay drops. The plant is switched off. The speed, with which the tension sinks over C6, is specified by the attitude of P2. It is connected with the time, which is necessary to be able to switch un the plant off. This time is between 1 minute un 10 minutes adjustable. One can set the automatic shut-off if necessary with S2 out of operation. After switching on of the plant on one must short circuit the relay contacts by means of S1. In this way the plant is only supplied with tension, and which can tighten relays of the switching off automat. The operating voltage for the circuit can be inferred from the plant (amplifier) and, if necessary, aud 12V to lower. In addition best an integrated voltage regulator is suitable. The power input amounts to with 12V for instance 15mA plus relay holding current. Finally still one: The relay tension must agree natural with the operating voltage of the circuit. In addition the maximum relay stream may not exceed 100mA. Otherwise T1 enters eternal hunt reasons.
Hope this helps others. I'll post a pcb layout later if anyone wants one.
Here's the circuit which I redrew:
I typed the text into altavista babelfish and it came out like this:
That does not occur at all so rarely: In the evening before the sleeping going still fast a plate presented and in the morning when waking up stated that the plant "laeuft" still;. That means: Eight (or more) hours unnecessary energy consumption. If the record player does not switch off automatically, then it is added still making more difficult that soon a new needle will be due. In order to make for all mark with the verschwendung a conclusion, Elektor a circuit developed, which does not fall also the sleepiest rear-Fi enthusiast into all too large expenses. With the help of this circuit the plant is switched off automatically after approximately 5 minutes break. How does such function a wonderful energy saver? The input signal comes from the exit of the preamplifier. It is strongly strengthened first of A1 and a2 and reached in this way some volt. With P1 one can stop the reinforcement between 47mal and 4700mal. The sensitivity of the circuit is thus in a large range adjustable. The joke of the circuit consists now of the fact that the plant is already switched off nich at longer music or sprechpausen. In addition still somewhat more than only the stage with A1/A2 is necessary. A3 serves as buffer/amplifier. Its output signal is "umgesetzt" by D1 parallelly and by C6 into DC voltage of the average value of the entrance alternating voltage;. If the tension lies over C6 above a certain value, then the exit of the Schmitt trigger A4 is "high", the relay tightens. If the tension sinks over C6, then the Schmitt trigger switches dei a certain value to "low", and the relay drops. The plant is switched off. The speed, with which the tension sinks over C6, is specified by the attitude of P2. It is connected with the time, which is necessary to be able to switch un the plant off. This time is between 1 minute un 10 minutes adjustable. One can set the automatic shut-off if necessary with S2 out of operation. After switching on of the plant on one must short circuit the relay contacts by means of S1. In this way the plant is only supplied with tension, and which can tighten relays of the switching off automat. The operating voltage for the circuit can be inferred from the plant (amplifier) and, if necessary, aud 12V to lower. In addition best an integrated voltage regulator is suitable. The power input amounts to with 12V for instance 15mA plus relay holding current. Finally still one: The relay tension must agree natural with the operating voltage of the circuit. In addition the maximum relay stream may not exceed 100mA. Otherwise T1 enters eternal hunt reasons.
Hope this helps others. I'll post a pcb layout later if anyone wants one.
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