Author Topic: Low power gateway  (Read 2499 times)

mielleriealphonse

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Low power gateway
« on: June 23, 2016, 07:00:42 AM »
Thank's to all the work of felix and all the moteino community I have been able to develop a low power monitoring system. It use a moteino coupled with a TD1208 modem and send data to the SIGFOX network. SIGFOX is a french IoT network covering France and several country around. it works great with very good performance in term of power : 4micro amp most of the time and 20mA during transmission (only 20s of transmission per hour).

The sensors are connected through wire. I am now interested in replacing this wire with a RF link. Of course this can achieve easily with to moteino equiped with a RF69. Source code of node/gateway and documentation are clear. Regarding low power, there is also several example using low power on the node side.

My difficulty is the following : the gateway part (moteino receiving sensors data) will also be battery powered. This system work outside with no power supply. Is there a chance to find a system that can sleep most of the time and wake up to check for reception ? In my case data of the sensor have to be send only once per hour.

I apologize in advance if the subject is already posted somewhere. I have spend days trying to figure out a solution without success.

Salutation from south of France !!
Very sunny here  8)

TomWS

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Re: Low power gateway
« Reply #1 on: June 23, 2016, 07:41:00 AM »
JoeLucid might have some ideas, but the thing that comes to my mind is that if all your nodes are in lowpower listen mode and the Gateway is in some kind of timed sleep mode (either listenMode timer, RTC, or WDT timer) then, when the Gateway wakes up to gather samples, it simply sends a wakeup burst to the nodes, the nodes wakeup and, on a well defined response time based on nodeId or somesuch, each node sequentially reports their samples to the Gateway.

This would be a low power alternative to the Gateway being on all the time, however, the burst (depending on your operating parameters) could be as long as 3 seconds and then, with the Gateway constantly receiving until it has received all the samples, the Gateway power consumption would be relatively high for several seconds which would quickly drain a low mAH battery.

An alternative is to simply deploy a dedicated Gateway that runs off the mains and gathers all samples from your other nodes as well as the Moteino you just deployed.

Good luck and have fun!

Tom

joelucid

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Re: Low power gateway
« Reply #2 on: June 23, 2016, 10:03:38 AM »
In theory you only need to time sync gw and nodes so the gw will be awake exactly when the nodes send. Practically speaking with Moteinos that's not so easy since they don't come with RTCs. So we've been using listen mode to make up for that.

Given that your nodes only send once per hour you could use the inaccurate timing sources the moteinos do possess (the wdt or the rc oscillator of the radio) to sleep around an hour on both nodes and gw. The timing will be off by up to +-10% so now you use listen mode to synchronize:

Put the nodes into listen mode with say a 200ms idle period from 1 hour - 10% to + 10% and wake from the gw with a 200ms pulse. Since the pulse is so short all nodes will be well synced after wake up and you can probably collect all measurements in 500ms or so.

Additional power requirement probably negligible over what sigfox requires. You can manage how the energy cost is split between gw and nodes by selecting the idle period.


mielleriealphonse

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Re: Low power gateway
« Reply #3 on: June 23, 2016, 06:00:08 PM »
Thank you Tom and Joe for your quick answer !

Both solutions sounds realistic to achieve the job.

However the idea to the use the lowpower listen mode seems to be much simpler as all the code is already available. One question remains : the power consumption of burst mode ? Do how have any idea of the value ? If i understand well this is a normal but continuous transmission of several seconds, the power consumption is the TX mode consumption of the RF69 i.e. around 45mA. Is that true ?

Jérôme




Felix

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Re: Low power gateway
« Reply #4 on: June 23, 2016, 10:11:16 PM »
If i understand well this is a normal but continuous transmission of several seconds, the power consumption is the TX mode consumption of the RF69 i.e. around 45mA. Is that true ?

Here's the power consumption breakdown, the RFM69W is at 13dBm output, 45mA, this is just for the RFM69 transmitter, also consider adding the MCU and anything else that is active:



You could run on small LiPos which can deliver a lot more than that, and even 100mA for a few seconds is not a lot for a LiPo, if you have the chance to use a solar panel to charge the LiPo during the day it could practically run forever.

mielleriealphonse

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Re: Low power gateway
« Reply #5 on: July 04, 2016, 04:36:07 PM »
Dear Felix,

I test your library with 2 Moteino equipped with RFM69W. I start from ListenNode_Gateway and ListenNode example and it works as described and perfectly. Very low current in low power mode and wake up on burst mode.

However I face a very big difficulty : the range is less than 50cm.

I test it with sevaral different motenio board. I reduce the connections at the minimum : only 2 moteino Lipo powered. Lipo are full charged and it is 5400Mah lipo, so it should be sufficient. I check the antenna soldering ... I check and test several time, including voltage measurement. But alway the same result : it works but only in a range of 50cm ...

I know that my problem is very vague. But maybe there is there some common mistake that I have probably done.

Jérôme

mielleriealphonse

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Re: Low power gateway
« Reply #6 on: July 04, 2016, 06:08:25 PM »
I have found the common mistake : hardware setup must be set very carefully. Default configuration of gateway example is RFM69HW, I have only RFM69W...

With good configuration it works perfectly !!!

jerôme

Felix

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Re: Low power gateway
« Reply #7 on: July 04, 2016, 06:46:11 PM »
Yay  ;)
Yes very common mishap, not sure how to make this more obvious, unless I make my own radio module that makes it easy to just read the configuration.

TomWS

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Re: Low power gateway
« Reply #8 on: July 04, 2016, 10:33:57 PM »
... unless I make my own radio module that makes it easy to just read the configuration.
I vote for that!