Switch on/off MP3 player by using transistor

Have you tried 100 ohm base resistor?

A BJT as a switch needs about 10% of the load current supplied to the base to saturate properly.

Your MOSFET isn't logic-level unfortunately, and some logic level MOSFETs are only good for 5V anyway.

ZTX851 is the best BJT I know for switching.

You don't have a 2N2222A ? That's the common switching transistor - only good for say 0.6A when
driven from an Arduino pin due to the need for 5 to 10% base current of course.

logic-level MOSFETs are the thing to use for higher currents.

I can't work out from the description whether this 3 volt module is being switched on the high side or low side.

Collector connected to MP3 module ground.

Can you supply a diagram ?

Ideally you'd switch it on the high side and use a pnp transistor (or p channel logic level mosfet ) and connect it like this if your Arduino is a 5 volt device:

This circuit is suitable only if the voltage you are switching is lower than than that of the Arduino. It is also inverted so a LOW on the arduino pin switches the module ON.

10k resistor will not work one little bit. 100 ohm like I said, and make it a good switching transistor (much
harder to find in PNP though).

Yes. You are right. I just looked for any diagram which illustrated high side switching. The resistor value must clearly be much lower in this case.

I'm still curious to see how the OP is attempting to connect it all up.

Which Mp3 module.
It probably has a low power standby command.
Leo..

Hi.
Many thanks for your reply.
This is the schematic I'm using.

You should not attempt to switch a module in its path to ground. That is OK with a relay or led etc. but not a module which may have multiple paths to ground.

Connect the grounds of the MP3 player and the Arduino together and make the transistor switch the path between the battery positive and the modules vcc.

Thanks 6v6gt
Something like this?

Can't do that.
An emitter follower will drop >=0.65volt (from 3.3volt), and more with higher current draw.
And the player could still be powered throught the (TX/RX ?) signal pins.

Post#9
I assume a DFplayer (don't have one).
Did you try the module's sleep mode?
Leo..

OK. Post a link to your player so it is clear what the minimum voltage is.

Also, it appears that your circuit is also dependent on the Arduino Uno being powered (by something) to give you 3.3 volts to drive the switching transistor. So it is not completely clear what role the 3.7volt battery has. Or are you intending at some stage to make the MP3 player into a stand-alone device ?

If power saving is an issue, then you should also focus on the Arduino Uno which, also when doing nothing, happily takes c. 50 mA.

OK.

The player needs 270mA and uses a 3.7v battery. I will check the minimum voltage needed.

It will be operated by a 3v3 "timer". This "timer" needs to be powered with, at least, 4.5V. And it uses a internal LDO regulator. It needs about 8mA.

The whole thing needs to be energy efficient. That is the reason I use the step-up regulator only to feed the "timer". I can use the step-up to provide 4.5 volts to the transistor but the system will be less efficient.

Thanks.

That diagram powers the Mp3 player with less than 2.6volt.

How are you controlling it.
I don't see any control/data lines.
The data lines will also power the device.
Leo..

The module will start automatically once powered by the battery (tested and working)
How can I increment the supplied voltage?
Thanks

Switching supply or ground and ignoring control lines might not fully power down the device.
It might even damage it.

If you insist on not exploring the sleep mode of the device, then use diagram#3 on this page.
Leo..

This one Wawa?

Thanks

As a reminder: I need to switch 250mA@3.7v (4.2-3.5v) using a 3v3 signal.

Yes.
Could replace the logic level p-channel mosfet for a PNP transistor if you don't have one.
At a cost of some switch voltdrop.
Q1 collector circuit needs to be changed for that.
Leo..

Thanks.
How much voltage drop will I have?
I will order those references. Any advice about better ones?
Thanks again.

Minimal if you use the right fet. The FDN340P seems to be suitable.
Don't expect to find a small logic level P-channel fet in a through-hole package.

Remember I warned you for the signal lines.
Leo..

Ok

I'm ordering 2n3904 and FDN340P.
R1=660 ohm
R2=1 kohm

Will the MP3 module be activated on uC High or Low signal?

Thanks again.