Author Topic: Consumption of Moteino 8Mhz and RFM69W  (Read 176 times)

Axamith

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Consumption of Moteino 8Mhz and RFM69W
« on: January 03, 2019, 04:54:44 AM »

Hello, what is the consumption of Moteino 8Mhz version?
I'm designing a device that works outdoors and I need to power the battery (Lithium 3.6V / 2600mAh). RFM69 will be broadcast once every 60 minutes. Due to low power consumption, I turn to RFM69W (45 mA). In the Moteino sleep mode, 100nA (great) is specified. What values is real if RFM is in listening mode?


I was looking at the Moteino R6 scheme and the power is filtered by a 10uF capacitor. Does this capacity cover current peaks when broadcasting? I wondered if it would be appropriate to connect the power supply (capacitor) when transmitting via a pin and a FET (P-channel) so that the energy does not get lost by maintaining the capacitor in a charged state. It makes sense?


P.S. sorry for google english ....

Felix

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Re: Consumption of Moteino 8Mhz and RFM69W
« Reply #1 on: January 03, 2019, 08:45:06 AM »
You don't really need the 8Mhz version. The regular Moteino will give you years of run time at such low transmission rate, with a 2600mAh battery.

The 10uF is there as regulator/power supply capacitor for the board MCU, it cannot sustain large peaks of attached peripherals. The battery instead can handle that, no need for special arrangements. The radio also has a 10uF on its own.

All you need is the Moteino with a CW radio (same as W). Even the HCW is good, when you use it with RFM69_ATC the transmission power can go down to only the necessary level, and help save battery life - this is what I recommend - use RFM69HCW unless you specifically have a very low range without unplanned obstacles.

See this page for transceivers reference: https://lowpowerlab.com/guide/moteino/transceivers/
« Last Edit: January 03, 2019, 09:58:01 AM by Felix »

TomWS

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Re: Consumption of Moteino 8Mhz and RFM69W
« Reply #2 on: January 03, 2019, 08:53:56 AM »
Hello, what is the consumption of Moteino 8Mhz version?
I'm designing a device that works outdoors and I need to power the battery (Lithium 3.6V / 2600mAh). RFM69 will be broadcast once every 60 minutes. Due to low power consumption, I turn to RFM69W (45 mA). In the Moteino sleep mode, 100nA (great) is specified.
I would suggest you use 5uA as a working average current when sleeping, if the radio is in sleep mode.
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What values is real if RFM is in listening mode?
if you use the smallest duty cycle in listen mode, which, I believe, is 64uS RX, ~2.8second listen interval, then figure another 3-4uA for this.  So, in listen mode, you should be able to average current less than 10uA for the whole system.  With a 60 minute interval, the duty cycle will be so low that the 'on' time is insignificant to the quiescent current.  Also figure self discharge of the battery into your calculations because this will be significant.

Quote
I was looking at the Moteino R6 scheme and the power is filtered by a 10uF capacitor. Does this capacity cover current peaks when broadcasting? I wondered if it would be appropriate to connect the power supply (capacitor) when transmitting via a pin and a FET (P-channel) so that the energy does not get lost by maintaining the capacitor in a charged state. It makes sense?
your concern is valid and diligent.  In practice, the existing capacitor appears to be sufficient due to the short transmit cycle and the low ESR of the batteries.  For coin cell powered circuits, I use a 100uF bulk capacitor.
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P.S. sorry for google english ....
No problem.  It's good enough!

Welcome to the forum.

Axamith

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Re: Consumption of Moteino 8Mhz and RFM69W
« Reply #3 on: January 03, 2019, 10:53:04 AM »
I did not think that the capacitor would hold the current peaks of the peripherals, only the RFM peak at the transmission when the take-off rises.

Moteino 8 MHz is essentially Arduino Pro mini without some peripherals (voltage regulator, LED ...). With him I got to sleep 3-4 uA. I also worked with the attached RFM69HW, but I did not get into sleep mode yet because I used a different library. It would not be a problem with your library, I'm about to go through the tests.
If I understand that well, RFM69 is still connected to the power supply (battery). The parallel connected capacitor should cover the transmitting tips. U RFM69W max. 45mA, at RFM69HW max. 130 mA (according to datasheet). And with power management and sleep mode, you're adjusting your energy performance.
In my case, I want to run several transmitters that will send measured data (temperature, weight) once every 60 minutes. So, Atmega and RFM could sleep for 60 minutes (8 second period).
The transmitting distance will be max. 50 meters, rather less. That's why I was thinking about RFM69W.

P.S. in the forum I read about RX, TX. What is going on, I do not focus on it.

Felix

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Re: Consumption of Moteino 8Mhz and RFM69W
« Reply #4 on: January 03, 2019, 01:20:05 PM »
Capacitors are always local and intended to the board they are near to.
Typically small bypass and filtering ceramic caps are there to support the closest devices. In this case the atmega328p MCU. Any peripherals you add have to have their own supporting capacitors. and filtering or they can cause power integrity issues the MCU board and other things attached to the same power bus.
Tom suggested a 100uF, that should be closer to your peripheral (radio module) to support an peaks you expect there.
But in my use I have not had a need ever to add any extra capacitors to any of the W CW HW or HCW RFM radios.
If there was a need for that, since Moteinos are generally used with RFM radios, I would have already included one on the Moteinos themselves, to save the user some hassle.
It's up to you if you really believe and determine you need one, I don't think you need it.
And splitting hairs and trying to save another 1-2 uA is really a diminishing return and low hanging fruit. Focus on other more important things. You have a gigantic LiPo, if you sleep your Moteino properly and transmit once a minute, you will really be bored and with more gray hairs before your battery runs out ;)

Axamith

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Re: Consumption of Moteino 8Mhz and RFM69W
« Reply #5 on: January 03, 2019, 01:34:41 PM »
I do not question the use of capacitors. It's a habit, for example, when supplying GSM modules I gave 1000uF to source covered large peak currents. RFM is obviously slightly different in energy consumption :-)

Felix

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Re: Consumption of Moteino 8Mhz and RFM69W
« Reply #6 on: January 03, 2019, 02:03:33 PM »
I do not question the use of capacitors. It's a habit, for example, when supplying GSM modules I gave 1000uF to source covered large peak currents. RFM is obviously slightly different in energy consumption :-)
For GSM we're talking AMP peaks :), Even those are very short pulses, a few ms so ... not really dramatic. But yes, a nice beefy cap is required to assist your regulator and ensure the power bus is stable and wont dip significantly.

For W/CW they peak in TX at ~45mA, of no concern at all.
HW/HCW peak around 130mA, no concerns there either.