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Using Arduino => Microcontrollers => Topic started by: LuisArduino on Jul 03, 2013, 03:11 pm

Title: Arduino & Xbee - In sleep mode xbee wakes up arduino because of change of voltag
Post by: LuisArduino on Jul 03, 2013, 03:11 pm
Dear All,

I have managed to make my relative and temperature sensors using Xbee and Arduino. However when checking the power consumption I noticed that in sleep cycle mode, the xbee wakes up for a little while and when it does it, the voltage drops a little in the CTS pin and the arduino things this is the wake up signal (CTS = LOW).
I dont know what else to do to avoid waking up the arduino (ATMEGA328P).
Any ideas with decoupling capacitors? maybe?
Thank you,

Luis
Title: Re: Arduino & Xbee - In sleep mode xbee wakes up arduino because of change of voltag
Post by: hiduino on Jul 03, 2013, 09:59 pm
If this a custom board and you don't have any decoupling capacitors, then yes you should always have them on every VCC pin and GND.  It will also help with better ADC readings as well.

Title: Re: Arduino & Xbee - In sleep mode xbee wakes up arduino because of change of voltag
Post by: LuisArduino on Jul 04, 2013, 09:25 am
Hi,

Thank you very much for your comment. I managed to fix the problem by putting another capacitor (100 uF) between the first pin (Vcc) and the regulator ground. Now the microcontroller doesnt wake up when the xbee does in between to remain connected to the wireless network.
One last question,  do you have a recommendation on the size of the capacitors?

Thank you,

Luis
Title: Re: Arduino & Xbee - In sleep mode xbee wakes up arduino because of change of voltag
Post by: hiduino on Jul 04, 2013, 10:34 am
Typical decoupling capacitors are 0.1uF (100nF) ceramic type.  These have much better high frequency response (better noise immunity) than the 100uF electrolytic type capacitors.  They should be close to the IC chip as possible to be the most effective.