Not all USB power supplies are created the same
We recently ordered a load of cheap (~£1.50) USB power adapters such as this one and started to notice problems, nanode missing posts, rfm12 problems, emonGLCD crashes and so we ordered another two: one branded htc another ~£4 unbranded one which work well. The more expensive unbranded one specifically outlined that it was better quality in the ebay description.
Using the sampler program we can shed some more light on whats going on here. So first here is the cheap USB power supply:
As you can see a lot of noise, a standard deviation of 6.4.
With the unbranded more expensive adapter the standard deviation is reduced to 1.5!
The branded htc adapter is pretty similar at 1.6
USB power direct from a laptop, should be as good as it can get. A standard deviation of 1.2
Conclusion: its worth ensuring that the power adapter is a good quality one in order to get consistent performance from the hardware.
To engage in discussion regarding this post, please post on our Community Forum.