Feather 32u4 FONA Current Draw

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bazhip
 
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Feather 32u4 FONA Current Draw

Post by bazhip »

Hey guys, I ordered my Feather FONA and am waiting for it to come and planning my project. Does anyone know the power draw on it when it is idling? Also, can you put it into a sleep mode and/or turn off the cellular radio in code? It seemed from the overview that you could ground a pin to turn it off, but I'm hoping to put it in a deep sleep and wake up briefly once every couple of minutes. Thanks for the help!

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adafruit_support_mike
 
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Re: Feather 32u4 FONA Current Draw

Post by adafruit_support_mike »

bazhip wrote:Does anyone know the power draw on it when it is idling?
It's way too uneven to use a single number, but estimate 125mA to 150mA for an average. The one I have hooked up now is ranging between 10mA and short spikes at 2A.
bazhip wrote:Also, can you put it into a sleep mode and/or turn off the cellular radio in code?
Not directly, but the KEY pin is exposed. You can connect that to a GPIO pin and pull KEY low for a couple of seconds to turn the FONA module on and off.

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bazhip
 
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Re: Feather 32u4 FONA Current Draw

Post by bazhip »

adafruit_support_mike wrote: Not directly, but the KEY pin is exposed. You can connect that to a GPIO pin and pull KEY low for a couple of seconds to turn the FONA module on and off.
Well thank you very much (non sarcastically lol). Could you possible update the Overview page to state that? In the overview, it says pull it low for 100ms. When you pull it low for 100ms, it turns off, but then magically turns right back on about 15 seconds later. It doesn't initialize properly by connecting to the network either. It just says there is no network connection. I figured the overview might be a typo, so I changed it to 1000ms, and same thing.. After rereading your comment, I changed the pull LOW to 2000ms and blamo, turns off and stays off.

That took way too long to figure out, but I'm glad it's working now. By disabling the SIM800H, it brings down the current to ~10mah. Luckily my setup only needs to check for texts about once every 5 minutes or so.

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absolutbeginner
 
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Re: Feather 32u4 FONA Current Draw

Post by absolutbeginner »

Hi bazhip or anyone else,
I try doing the same and wonder why the serial monitor does not show whats happening when re-powering the module.
Just setting an output low and high again to see the changes and programm working.
But when toggeling the KEY to ground and the module turnes off and the same to turn it on again, the serial monitor does not show anything and my output does not change. I fear the module does not start the code.
Instead when I upload my code and start the serial montor, everything works fine. (???)

Any idea?

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amyers
 
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Re: Feather 32u4 FONA Current Draw

Post by amyers »

Its a bit late now, but possibly for future reference, I would look into using the AT+CFUN=? command if you're interested in reducing power and not necessarily turning off the fona.

From the simcom datasheet, modes are:

0 Minimum functionality
1 Full functionality
4 Disable phone both transmit and receive RF circuits

I would think setting # 4 would achieve something similar to a 'sleep mode,' but I haven't tried it yet.

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absolutbeginner
 
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Re: Feather 32u4 FONA Current Draw

Post by absolutbeginner »

Hi amyers,

thanks for your reply, I already tried this and it still took too much power - I don't know the amount anymore.
I had to have no power when turned off, but with an external interrupt wake up and send an email.
Then go to "sleep" (better turn off) again.

I now realized it with an external circuit:
X1.1 is my battery-supply "+",
X1.2 is my battery "-"
X2.1 and X2.2 is an external switch normally open
X4.1 and 3.4 is voltage supply at my FEATHER and
X4.6 is connected to a digital output.
When connecting the battery, nothing happens.
Then closing the switch on X2.1 and 2.2 gives the supply to the FEATHER
After having fulfilled the program (sending an email), the DO is set and the supply is cut from the FEATHER.
To release this circuit I have to release the switch (X2.1-X2.2) by hand and everything starts from the beginning.
By this I hope to be able to use the battery at least one year with one daily email.

Hope this may help others, too.
Attachments
PCB1.pdf
external circuit
(13.83 KiB) Downloaded 101 times

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