arduino power necessary?

Hey all,

i'm currently making a pulse oximetre using texas instrument's AFE4490 to gain digital result from my photodiode (NJL5501R),

I want to ask regarding the power. So in my AFE4490 chip, some pins required 3.3V and 5V, however it is already powered by its USB cable. Therefore, I do not use the 3.3V and 5V that is provided in the arduino. But, my system does not give any feedback from the photodiode, though all LEDs both in the arduino and the AFE4490 blinks showing the system is well-powered.

So i am wondering if actually it is necessary to use the power 3.3V and 5V from the arduino for the chip? or it is fine if i rely on the USB cable power on the chip itself?

I know my question is very noobies especially for experts like most of you, but I hope someone is kindly willing to enlighten my confusion.

Stella

I suspect a schematic is going to be necessary. Even just scribbling something on paper and then taking a picture can be very helpful.

Try to keep the image around 1024 x 768. Under Additional Options you can attach files to a post.

@Coding Badly

I agree with you, here you go. :slight_smile:

In this situation powering external source not needed.

stellalaksono: So i am wondering if actually it is necessary to use the power 3.3V and 5V from the arduino for the chip?

It is not necessary.

or it is fine if i rely on the USB cable power on the chip itself?

It is fine.

All three devices (Mega, level converter, AFE4490) need to have grounds (GND pins) connected together.