Bluetooth distorts analog read? I'm working to make a simple pedometer with Arduino, and after managing to find an algorithm that correctly finds the steps, I added a bluetooth extension (the overly popular and cheap JY-MCU) to check the steps via bluetooth.
I am facing a strange issue, though: when the bluetooth device is powered and waiting for a connection (red led blinking) the analog read function that reads data from the accelerometer goes crazy (thus the pedometer finds a step each second or so). When the bluetooth is powered down or connected to a device such as a mobile phone this doesn't happen.
Did anyone have this problem before? What could be the issue? My setup is easy, you can see it on the image.

I had other sensors as well but since the problem stays even when there are only those two connected I posted the bare minimum setup.
At first I thought I could use some kind of pull-ups to stabilise the signal, but I really have no idea on where to tie them and if they can really be helpful at all...
Any help is appreciated.
You can try decoupling the power for the bluetooth:



The resistor value should be tiny - 10Ω is a good value to use - don't go much higher than that.  The capacitor should be nice and big - I have shown 100µF, but bigger is better - whatever you have that's nice and big.  (Make sure you wire it the right way round - check which pin is marked as -)  You might also want to add a small capacitor (say 100nF) in parallel with the large one.