Choosing the right transistor type

Hello folks,

I'm building a multi function player (MP3, AUX or FM radio), and I'm adding switches which will control what you'd like to use currently (MP3, AUX or FM radio). The way it works is when you choose different modes, you will be controlling supply input of the modules for MP3 and FM radio, and for AUX input, R and L channel.

Long story short, I need to chose a proper transistor type (could have used relays, but they're larger and more expensive) that could control that. Note: the transistors won't control and special high voltages and amps. Also, I need a type that won't have a large voltage drop, because my modules require precise supply voltage.

Also, it needs to be arduino compatible, nothing too large for it.

Any other ideas are surely welcome.
Thanks in advance!

Analog multiplexers?

Don't you mean demultiplexers? As I have a single input, and multiple outputs.

But still, a great idea! Would never come to that idea myself.

One question, are there any voltage drops over a demux/mux?

They are both multiplexers and demultiplexers. Basically, analog switches.

Yes, there will be a voltage drop. But that will also happen with any kind of transistor switch. Only relays can avoid that.

Alright, thanks!
Seems like relays are the way to go, sadly! I have some spare ones anyways, but still.. controlling <100mA with a 10A relay is just pointless, but hey.

Thanks a lot for the help.

You can get much smaller relays, ones that use reed switches and very small coils.

Better still may be changeover relays. More tricky to operate, but the coils only need to be energised for the split-second of changeover, not for the entire duration of the source being selected. That reduces current consumption and noise interference.

PaulRB:
Better still may be changeover relays. More tricky to operate, but the coils only need to be energised for the split-second of changeover, not for the entire duration of the source being selected. That reduces current consumption and noise interference.

Latching relays.

Paul__B:
Latching relays.

Yeah, what he said!

There is no problem to use a MOSFET here. Everything has a voltage drop, even a relay. Choose a MOSFET with Rds(on) in miliohms and with 100mA of current the voltage drop will be in mV range. Comparable to power supply wires. Look into datasheet for Rds(on) @ Vgs 4.5V (or less), and choose a MOSFET with low enough value. Unless you need to switch it often you can take any. ("Often" means a few times per second which would destroy a mechanical relay anyway.)

You are switching power to different modules. That means high-side switches are required. You could build a circuit with 2 transistors per switch or you could buy the switches.

Relays were mentioned but Pololu make a nice line of high-side switches that are probably better than relays for your project.

Also keep in mind that signals going to modules that are powered off might not be a good idea.

MorganS:
You are switching power to different modules. That means high-side switches are required. You could build a circuit with 2 transistors per switch or you could buy the switches.

Why do you need high side switching? I see no reason for this.
Why do you need 2 transistors for high side switch if they have the same supply voltage?

ElCaron:
Also keep in mind that signals going to modules that are powered off might not be a good idea.

If I understand it correctly OP wants to connect OUTPUTS of different modules, only one of them powered at time. Unless the outputs are protected somehow this may lead to real trouble too.

XGamer223:
The way it works is when you choose different modes, you will be controlling supply input of the modules for MP3 and FM radio,

But maybe we are mixing up "power supply" and "audio signal"?

Smajdalf:
If I understand it correctly OP wants to connect OUTPUTS of different modules, only one of them powered at time. Unless the outputs are protected somehow this may lead to real trouble too.

That, and he may have some common control electronics?