On Wed, Jul 11, 2012 at 2:37 PM, Tilman Baumann
<address@hidden> wrote:
On 02/07/12 15:56, Gareth Roberts wrote:
I hooked up the oscilloscope and gave it a test.
The ripple is low, not more than I had on the power supply. Noise seems fine to me. But I'm not a expert.
The first really weird thing is, that zero is at 2.5V. Negative pressure is from 2.5 to 0 Volt. (WTF?) And positive windspeed is 2.5 to 5V.
That is bad in two ways. First, for the ADC I would rather have 3.3V[max]. And what is the deal with negative pressure?
And also, there is very little response to actual wind. My relatively powerful desk fan does not even create a recognizable response. Blowing at it does, but only very little.
I would guess that you need insane speeds to saturate this sensor.
To increase accuracy I would have to remove that 2.5V offset. Which would also move me in the range of a 3.3V ADC.
I could hook up a op-amp with one leg on a 2.5V reference. But my wiring is already insane, don't want to make it worse.
I would have to sacrifice LED to get a usable ADC already. I'm beginning to really dislike that whole idea...
Damn. The Eagletree sensor was not that much more expensive. And digital. And calibrated.
Kids, don't try this at home I would say. It's not worth it.