Would you like to leverage a pre-built module perhaps such as @Hearinspace linked to in #13 above?
Could be modified to interface it with your LED voltage control signal, or something similar could probably be interfaced to the LED voltage. Or, you could make something more or less from scratch.
Another question would be whether you would like the dac to be in mute mode by default or unmuted by default. IOW, do you want the relay to be energized during a mute, or un-energised during a mute?
Could be modified to interface it with your LED voltage control signal, or something similar could probably be interfaced to the LED voltage. Or, you could make something more or less from scratch.
Another question would be whether you would like the dac to be in mute mode by default or unmuted by default. IOW, do you want the relay to be energized during a mute, or un-energised during a mute?
I suppose any thing that might avoid the POP would work for me. And my less tolerant “better side”. Can’t blame her. My speakers are very sensitive, so these pops are really jarring! I was thinking that the relays would be N.O., and closed when energized. How would I modify that device to work off the LED voltage?
Use a transistor to monitor the LED voltage (with a current limiting resistor). Then use that to trigger a timer which controls the relay, maybe such as a CMOS 555:
https://www.ti.com/lit/ds/symlink/lmc555.pdf?ts=1747374344159
Also: https://archive.org/details/IC_Timer_Cookbook_1st_Ed_1977_Walter_G_Jung
https://www.me.psu.edu/cimbala/me345/Lectures/The_555_Timer_IC.pdf
http://www.sophphx.caltech.edu/Physics_5/Data_sheets/555appnote.pdf
Don't know how much help you want or need, but I think its good if you are willing to take this as an opportunity to learn maybe a little more about how to diy this type of thing, then maybe worth doing a little reading. Feel free to ask any questions if you want. Or if that's not your thing then we can help more directly.
What I would suggest to do if you want to use a preexisting module, is read about how timers work, then use that to figure out how the module works. From there its only a short bit more to trigger a timer from your LED signal. OTOH, if you want to make something from scratch then that's fine too. In any case, you need to decide how you would like to proceed from here.
Reason I suggest trying to figure out for yourself as much as you can is because its an extremely useful skill to have once you start to get a little experience under your belt.
https://www.ti.com/lit/ds/symlink/lmc555.pdf?ts=1747374344159
Also: https://archive.org/details/IC_Timer_Cookbook_1st_Ed_1977_Walter_G_Jung
https://www.me.psu.edu/cimbala/me345/Lectures/The_555_Timer_IC.pdf
http://www.sophphx.caltech.edu/Physics_5/Data_sheets/555appnote.pdf
Don't know how much help you want or need, but I think its good if you are willing to take this as an opportunity to learn maybe a little more about how to diy this type of thing, then maybe worth doing a little reading. Feel free to ask any questions if you want. Or if that's not your thing then we can help more directly.
What I would suggest to do if you want to use a preexisting module, is read about how timers work, then use that to figure out how the module works. From there its only a short bit more to trigger a timer from your LED signal. OTOH, if you want to make something from scratch then that's fine too. In any case, you need to decide how you would like to proceed from here.
Reason I suggest trying to figure out for yourself as much as you can is because its an extremely useful skill to have once you start to get a little experience under your belt.
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With muting relays, I've found that NC types (closed = muting on) are more foolproof.
Don't ask me how.
Don't ask me how.
IIUC all you need is having the the output muted all the time, and unmuted when the lock LED is on, with a delay to avoid the initial thump. IMO a simple delay circuit triggered by the LED voltage would do. (ON delayed, OFF immediate). IMO one 74x04 inverter and one 74x123 monostable multivibrator would do. Delay circuits with 74x123 are quite common, I have used it a few times to modify/fix behaviour of home electronics.
This is a trivial simulation of 74123 + 7408 AND https://falstad.com/circuit/circuit...BL69Wca5oaxLVKWfGx2rhwqXv66hrA+geRHLorVMv02IA . It's not ideal, because there may be a collision glitch at ON (before Qneg flips to low) but it would be too short for a relay. For a transistor the circuit would need fine-tuning to avoid the possible tiny glitch
This is the vital information needed.
It may be possible to use little more than a reed relay set up to permanently short the audio out and where the relay opens after the LED has been lit a couple of seconds.
That makes it pretty easy to add a simple mute non invasively.
You add a normally closed relay like a double pole double throw type that has the normally closed contacts wired across the audio outputs. That shorts the output of the DAC so no noises. To open the relay the coil is driven from something as simple as a high gain Darlington transistor with a resistor/capacitor time delay on the base. Even better a FET, but I can't just think of one that has a low gate/source voltage which is needed here let alone have a model for one to simulate. The circuit however remains the same but the FET allows a much higher R value and a lower C.
Like this. Its as simple as it gets. To pursue the idea the supply voltage available is needed to choose a suitable small relay like a reed relay type. The sinple design means it can be made 'dead bug' style neatly (no pcb needed) and the relay glued neatly into a suitable location.
Supply in red here comes up 1 second in and the relay opens another second after that (in blue). With a FET longer delays are easily done with more suitable values. Darlington transistor type shown isn't the best option but would still work. Small outline Darlington's are available though but a small FET would be much better.
R3 and D1 are your LED and supply feed already present.
R1/C1 set the delay.
D2 probably isn't needed in normal use and is to discharge the timing cap on power off ready for instant operation again.
No diode added across the coil because the switching times will be slow and should not cause any back emf. Trying to make it as simple as can be.
Edit... it also seems a high gain small signal transistor might work well too instead of a Darlington. Something like a BC546.
You add a normally closed relay like a double pole double throw type that has the normally closed contacts wired across the audio outputs. That shorts the output of the DAC so no noises. To open the relay the coil is driven from something as simple as a high gain Darlington transistor with a resistor/capacitor time delay on the base. Even better a FET, but I can't just think of one that has a low gate/source voltage which is needed here let alone have a model for one to simulate. The circuit however remains the same but the FET allows a much higher R value and a lower C.
Like this. Its as simple as it gets. To pursue the idea the supply voltage available is needed to choose a suitable small relay like a reed relay type. The sinple design means it can be made 'dead bug' style neatly (no pcb needed) and the relay glued neatly into a suitable location.
Supply in red here comes up 1 second in and the relay opens another second after that (in blue). With a FET longer delays are easily done with more suitable values. Darlington transistor type shown isn't the best option but would still work. Small outline Darlington's are available though but a small FET would be much better.
R3 and D1 are your LED and supply feed already present.
R1/C1 set the delay.
D2 probably isn't needed in normal use and is to discharge the timing cap on power off ready for instant operation again.
No diode added across the coil because the switching times will be slow and should not cause any back emf. Trying to make it as simple as can be.
Edit... it also seems a high gain small signal transistor might work well too instead of a Darlington. Something like a BC546.
Thanks Molly. This is right up my (limited) alley! Would a 3V relay like this work?https://www.alldatasheet.com/html-pdf/1244443/EVER-WAY/HK19F/445/1/HK19F.html
Yes and no. Any reason for choosing that one? Its a very strange data sheet, I can't figure out what is meant by these different resistance figures for the coil. Maybe there are different coil values available in each voltage... which would be kind of odd. You would definitely want the 60 ohm version.
We really need to know the voltage of a suitable rail in the unit that can be used. An unregulated rail is usually perfect. 3v is very low for a relay and it means the coil is correspondingly low in resistance which means it draws considerable current.
Search the forums for Molly. Happens all the time 😉