(I moved this to Project Guidance, seems more appropriate.)
Hi,
I would like to use the digital outs on a nano to switch on or off an audio speaker signal just by disconnecting + or -. What type of MOSFET (or other solution) would be suitable for this, taking into account things like ac signal, impedance?
Thanks!
Can you give some more details about your speaker please.
Where is it getting it's audio from?
What is the signal level going into the speaker?
Does what ever drives the speaker have to be isolated from the Arduino? - I suspect it does.
Do you have a ground signal from what ever drives the speaker?
This project is not as simple as you might think.
There is probably also a better way of achieving the same thing, like cutting power to the amplifier. What type (class) of amplifier is it and what is its power/voltage rating ?
Context: I am making small sculptural prototypes for an interactive sounding art installation. The user control a soundscape by touching objects. It may be that some type of feedback from the object itself is needed to achieve an immersive experience. Or not.
I am about to place an order for electronic components that I will/may need, and that is why I ask around at this early stage (my post about haptic feedback is connected to the same project).
In this prototype I want to use one or two channels of audio and when a user active a sound by touching an object (all) audio is routed to this object (here would be the MOSFET) even if only one voice is affected. There will be somewhere between 3 and 8 objects and each object has its own voice (sound).
This way I do not have to use a multi channel sound card and can stick with one 1-2 channel amplifier for interaction feedback. The major part of the sound image will come from complementary full range speakers. The objects themself only has to be heard vaguely or even just give vibrations under the users hand.
The objects are between 10 and 20 cm in diameter and I will place the speaker inside or behind each object. The speakers are harvested from laptop speakers and hifi speakers.
The audio should be coming from a sound card connected to a Raspberry Pi. I have not decided on amplifier, while experimenting I use random hifi amplifiers.
I work with recycled materials and I always aim for the most low-tech solutions, but I still want to know the "right" way to do it. And in the end nobody except me should risk their health (like getting an electric chock).
Lenghty explanation but I hope it shows how I am thinking. Thanks!
Well it is very different from your original description.
Am I right in thinking that you now want to connect several speakers to one sound source and have all but one disconnected in some way?
It sounds like a job for relays.
Yes, that is what I want to do. I have some relays that should work, but would it not be possible to do it with MOSFET? Or why would it not work?
It’s is simpler to use relays, because the biasing you will have to do to handle the AC signal.
This is because the signal will swing below the negative or ground signal. You might use an analogue data selector but get the type that allows you to add a negative rail. You will need an other power supply or voltage mirror to provide this rail.
The relays I have are quite noisy (the solenoids). If I recall correctly they can handle high power.
Could you recommend relays that would be enough for my purpose and maybe not so noisy?
Look for reed relays they are very quite.
How much current are you switching for the little speakers?
Perhaps Sold State Relays would suffice, such as PVT212, can handle 800mA at high AC levels.
https://www.mouser.com/ProductDetail/Infineon-IR/PVT212PBF?qs=9%252BKlkBgLFf08WIN5p81c8w%3D%3D
I offer 8 of them on a board, turned on by shift register controlled by an Arduino.
Youtube:
Either would do. Note you need a coil to wrap round it.
I would suggest you at least start with a typical Relay Module.
Its a low risk option so you won't have to troubleshoot a more high-tech design. And you may find you can wrap it in some sound deadening material and not have a noise issue.
Else you can later on add a solid state higher tech solution. But at that point you will have a working solution as a baseline.
Reed relays might work but be careful the reed switches in these relays are not very robust. The contacts can stick (actually weld closed) with not a lot of power. When working with electronics there are two criteria:
I have this one, it works, but with lot of clacking. And external power is needed.
The switching will not be rapid but the sound will always be running when switching on and off.
I was thinking that I in some way could use capacitors to make a small ramp in level. Maybe something like that would also protect the switch (reed or not)?
The problem with that is that a capacitor large enough to make a ramp is also large enough to completely remove any signal.
pam8610 has a mute switch, use it for each speaker.
But that would mean using one amplifier for each speaker he has.
1 amplifier is cheaper than 1 relay
After some additional thinking, you might be able to use a 4 quadrant logic level triac. You would have to have the triac connected to ground and the speaker between the triac and the audio output.
However I have no experience with triac's in this type of application.
Triacs are meant to conduct AC power and normally not low level signals. But you do have an AC signal. The "4 quadrant" type of Triac allows you to turn it on with a positive signal to the gate even though the input signal is / can be negative with respect to the common connection.
I have use triacs in a low voltage situation in this project:- RFID Sequencer
This is the schematic of how it is used:-
The triac is a BT131 and is in parallel with the receiver coil. I used it to short out the coil for readers I was not interested in, to prevent the coils acting like passive radiators and making one token look like it was on many readers.
