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Barometer module doesn't work with battery/usb


#1

Hi,
when I power my FEZ Spider with the power adaptor from the socket , my barometer module works fine and displays me correct values (temperature & pressure). However when I power it with a 9V battery or USB I get crazy values for pressure (-300 to 1000 hPa) and temperature (-10 to 50 °C). They are not constant, they change after each measurement interval. What’s the problem here?


#2

Not enough power will be my guess. Do you use same power module in both cases?


#3

Yes, it’s the same power module.


#4

Maybe the sensor needs an accurate 5V and using USB will probably not give you that. You can measure the 5V line and compare maybe.


#5

It looks like on its own this module should work fine from any source. But I guess you have some other power hungry modules attached (display at a minimum). This can be a reason too.


#6

@ Gus
I checked the description of the sensor and its supply voltage is in 2.2v-3.6v range.
http://www.hoperf.com/sensor/barometer_sensor/hp03m.htm


#7

Then this is even more strange now :slight_smile: I have no logical explanation.


#8

Hmm I think my display was very power hungry :wink: I changed the code now:
First initialize the barometer, then wait for a short time, then turn on the display and everything works fine :slight_smile:

Thanks