Can I power 3 ky-038 from Arduino Uno's 5v out?

Basically the question. Can I power 3 of ky-038 from arduino?

Because using an external 9V battery only outputs noise and the sensor keeps giving 1023 or 0 on the analog input of Arduino. The sensors work fine without the battery tho.

For informed help, please read and follow the directions in the How to use this forum post.

The only thing on that module is an LM393 and a led.

The LM393 draws less than half a mA.

Short answer is YES.

This means nothing without explaining what you connected the 9V battery to.

Because using an external 9V battery only outputs noise and the sensor keeps giving 1023 or 0 on the analog input of Arduino. The sensors work fine without the battery tho.

raschemmel:
This means nothing without explaining what you connected the 9V battery to.

Nothing right now. The battery goes into 7805 Voltage regulator that outputs 5V that goes into the mic. And as soon as I do that: the mic's output become random. Jumping between 1023, 600 and other random values

Is the module GND common with the arduino GND ?

Also, I am not seeing the need for the battery.
Why don't you forget the battery and just connect the module V+ to the arduino Vcc and GND to the
arduino GND ?

Is there a connection between the 9V (smoke alarm battery ?) and the arduino ?

If so, that battery is only rated for maybe 300mAh, meaning an arduino (that draws about 55mA) will only run (300/55)= 5.45 hours maximum.

dydx:
Basically the question. Can I power 3 of ky-038 from arduino?

Yes.

Because using an external 9V battery only outputs noise and the sensor keeps giving 1023 or 0 on the analog input of Arduino. The sensors work fine without the battery tho.

Then obviously there is your problem. How is it all powered without the battery?