Speaker interferes with nRf24l01 radio sensitivity, power ripples?

Other Hardware General Electronics
1

I have a project where I have 2 arduino's connected via i2c.
Arduino 1 is used as a sound module that plays WAV files from a SDcard.
Arduino 2 is used as a radio module that sends and receives messages using a nRF24L01+.
Arduino 1 has a AF8002 Audio Amplifier to boost the volume to a connected speaker.
Power is shared between both boards (3.3v) (shared regulated LiPo)

The problem I have is that when I attach bigger speakers the radio does not receive wireless packets. Using small speakers like 8ohm 0.5watt works fine, for bigger speakers like 8ohm 2watt I need to add a larger capacitor the power(1000uf) which works but does not work if going for even larger speakers.

I suspect the issue is due to the speaker causing power ripples that affect the nRF24L01+ sensitivity, it does not affect the nRF24L01 from sending packets just detecting them. Issue is only present while playing sound.

My question is what is the best way to solve this issue? Do I need to add chokes/coils or low pass filters to clean up the power between the boards?

Af8002 datasheet http://www.chinesechip.com/chip/documents/435db5c615b8457e95817a6ccbccf372_0.pdf

2

Try powering the amplifier direct from battery, I think the regulator cannot handle enough current.

3

Sounds like a power supply problem to me, ie. your power supply doesn't have enough amps to drive the speaker.

As you've seen, a capacitor will help smooth out the peaks in demand, but it can't help when there simply isn't enough power.

4

By adding a bigger capacitor (3300uf) it seems to fix the problem and I can us a 3w speaker but is there a better way?

Using unregulated power from the Lipo I was also having the same issue.

5

You need to put an oscilloscope on it to watch the voltage while it's playing. That will tell you where the problem is.

A fast multimeter might also show the problem. Watch the voltage and see if it varies.