Author Topic: Making a lower power Moteino  (Read 26673 times)

Felix

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Re: Making a lower power Moteino
« Reply #60 on: September 08, 2016, 09:39:02 AM »
I didn't say it won't happen. I plan to make a new Moteino type some time in the (near?) future. I just have to be very careful in what I put on it. IOW it's my job to make sure this will be a desirable node with features (including low power) that will distinguish it from the others, such that people will buy it and find it easy to use at a reasonable price. Otherwise I am wasting my time and money developing something that will be wanted by 10 people who are extreme low power fans. Will it be as described here? I don't know yet.
Sure, 20uA is great, but is 20nA vs 4uA worth the cost/complexity increase and usability decrease? I have to carefully evaluate that. There's a point where going so much lower power makes no sense because batteries shelf life don't last as long as that node could, or because technology changes and may obsolete that hardware, or because the owner won't live 50 years more to see that node deplete its battery.

kobuki

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Re: Making a lower power Moteino
« Reply #61 on: September 08, 2016, 09:51:46 AM »
Yes, I completely understand the reasoning. Though I think a new sister in the existing Moteino family could be sold by its established brand name. Imagine "New moteino using even less power!" :) You're well-known in the field and this relatively small, but ever-growing hobby and semi-pro market. For me the most useful change would be periodic wakeups with a precision timer (+RTC) and the possibility to add batteries below 3.3V like 2xAAA or CR123 without a mod. I agree, going below a certain sleeping power is senseless.

Felix

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Re: Making a lower power Moteino
« Reply #62 on: September 08, 2016, 10:31:11 AM »
Sure, all things to consider.
The one challenge and consistent theme I see is that no matter how wide range of features a board has, someone wants something else.
I guess focusing on low voltage and low power may be the delimiter between the general purpose Moteino which works with inputs up to 16v, and this new node type that can go to 1.8v perhaps.

ChemE

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Re: Making a lower power Moteino
« Reply #63 on: September 08, 2016, 10:49:07 PM »
I echo what others have suggested especially the RTC and Si7021 although the HTU21D has a lower sleep current if the datasheet is to be believed.  Getting back to fuses, would it make sense to fuse them to have BOD disabled so that they resume from sleep faster?  Also what about selecting components that are stable down to 1.8V as a method of further reducing power consumption?  There was some discussion as to whether or not the RFM69 could work at 1.8V but I didn't see anything conclusive.  The picopower uC's are good to 1.8V and the TH sensors are as well.

Felix

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Re: Making a lower power Moteino
« Reply #64 on: September 09, 2016, 08:13:12 AM »
The RFM69W will work at 1.8v "officially". The RFM69HW has an RF switch that requires 2.4v, but others have reported it working down to 1.8v without problems.

kobuki

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Re: Making a lower power Moteino
« Reply #65 on: September 09, 2016, 10:26:20 AM »
I echo what others have suggested especially the RTC and Si7021 although the HTU21D has a lower sleep current if the datasheet is to be believed.

I think putting on all kinds of sensors is not a very good approach. This is the point where it's very hard to satisfy everyone. There exist various easy to use modules and even LPL shields for T/H measurement and other things. Having a general purpose LDO-less board with a(n optional) timer or RTC would be simpler for both the manufacturer and the clients. Maybe solder-clad footprints for adding several kinds of sensors would be nice. For instance, Si7021 and the HTU21D are interchangeable IIRC. Setting clock source or BOD fuses is a somewhat more advanced task but can be done any time after purchase when flashing.

ChemE

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Re: Making a lower power Moteino
« Reply #66 on: September 09, 2016, 04:20:48 PM »
Felix,

You asked on the previous page about battery discussions.  For projects I see myself taking on running for 2 decades outweighs being easily swallowed so I prefer to run off 2xAAA rather than a coin cell.  2xAAA are also almost exactly the same width as a Mote just a bit longer; gives enough room to add a WDT and a footprint for a Si7021 (or Si7034 if we want to go nuts on lowest power).  An arduino+radio that can run on 2xAAA for 10+ years and fits in your mouth; surely that would sell.

PS thanks for the lightning fast processing and shipping of my two TPL5110s!

Felix

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Re: Making a lower power Moteino
« Reply #67 on: September 09, 2016, 05:46:31 PM »
For projects I see myself taking on running for 2 decades outweighs being easily swallowed so I prefer to run off 2xAAA rather than a coin cell.
An arduino+radio that can run on 2xAAA for 10+ years and fits in your mouth; surely that would sell.

PS thanks for the lightning fast processing and shipping of my two TPL5110s!

I agree and would rather do AAA than coin cell which will be a black hole of support for the outraged pack that will discover coin cells won't yield 10km at full TX power and isn't as plug and play as the "industry standards". 2XAA(A) can do all that with the defaults, well even now with a regulator-less Moteino. I like the easy to swallow concept :) Maybe my next company will be Swallow Labs, where everything made is can be easily swallowed, lol.

PS: My pleasure ;)

MoebiusL

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Re: Making a lower power Moteino
« Reply #68 on: September 29, 2016, 10:01:35 PM »
I built a very simple temperature sensor node some time ago that basically reads the temp from a TMP36 and sends it to a base station (a Moteino) every 4 seconds and sleeps (the real application will be sleep for much longer, but I'm speeding things up just for testing).

I've been trying to run Moteino from Li-Po for while, but for long running applications didn't work very well because of the self-discharge I guess. Also tried 2xAA without regulator and was only able to run down to 1.2V per cell as mentioned before on this topic (maybe because the TMP36 needs at least 2.4V). Also tried using 3xAA with the regulator but didn't get much of it either, it's a shame that RFM69 does not support 5V, so I could connect the 3xAA directly!

The idea of running at very low voltages is great, but I think it's challenging to have all sensors and components running at 1.8V... maybe in the future new sensors will lower the working voltage to help us  :D

I'm now testing some boards called Whisper Node, that I got from Kickstarter (https://bitbucket.org/talk2/whisper-node-avr/overview). They are quite similar with the Moteino but there are loooots of tiny components. At the moment I'm running a similar basic temperature node with a single AA cell. The board has a step-up and when things are at sleep consumes a bit over 5uA from the battery, the whole board runs at 3.3V and MCU+temp.sensor seems to be happy.

The one thing I didn't like much is that many pins from the MCU are already used by the Whisper Node itself, like 2 voltage dividers, 2 leds and 2 buttons... it can be handy if you're using those, but won't be my case. Apparently you can cut the traces to free the pins for your own use, but just feels like I'm destroying the board - I guess everybody has different needs as Felix mentioned.

Well I'm just running the board for 3 weeks now and still can't notice a real voltage drop of the battery, I'll try to post something back when I get a bit more results... but I guess a step-up regulator might be the answer for lower voltages. I'll try to get a stand-alone step-up regulator, maybe this one: https://www.pololu.com/product/2561 to replace the LDO on one of my Moteino to do some testings as well...

kobuki

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Re: Making a lower power Moteino
« Reply #69 on: September 30, 2016, 05:22:47 AM »
Interestingly what you write doesn't really coincide with others' experience. Did you measure the power consumption with the original regulator-less boards during sleep? 2.4V is sure to be a limiting factor, though.

MoebiusL

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Re: Making a lower power Moteino
« Reply #70 on: October 01, 2016, 07:44:10 AM »
@kobuki, yes and the consumption was very low, never more than 2-4uAs. The problem with regulator-less is that the whole thing starts to become unstable as the AA voltage drops below 2.4V, even reducing the speed, as seems that the sensor doesn't like it. Even with some good results, at the end it was leaving lots of un-usable energy in the batteries.

That's why I'm doing some experiments using step-up regulator options, to try to extract as much as possible from the Alkaline AAs even if it cost extra 1uA or 2uA during the sleep. But at the end I'm getting a stable 3.3V all the way down to 0.8V on a single cell (I hope, as the tests still running).

perky

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Re: Making a lower power Moteino
« Reply #71 on: October 01, 2016, 07:54:32 AM »
One big problem with boost regulators is their start-up current, it can cause a current spike of several hundred mA if you're not careful. This is a problem when batteries are depleted because their internal resistance shoots up, a large current spike will drop the voltage to below the working threshold which will necessarily require the end point of the batteries to be higher . So you need some kind of slew rate control on the output of the boost regulator, or a programmable soft start.
Mark.

kobuki

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Re: Making a lower power Moteino
« Reply #72 on: October 01, 2016, 07:59:09 AM »
@MoebiusL, have you thought of using some other kind of temp. sensor that can go lower?

joelucid

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Re: Making a lower power Moteino
« Reply #73 on: October 01, 2016, 08:13:26 AM »
I would recommend to ditch the tmp36 for a si7021 and run off of 2x aaa without regulator. Sleep using the radio as wake-up timer gives you around 1.3uA sleep current. This is much simpler, quieter and more power efficient than using a booster. It would operate down to around 1.9v. Prepare not to change batteries in your life if using lithium cells.

TomWS

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Re: Making a lower power Moteino
« Reply #74 on: October 01, 2016, 08:32:14 AM »
That's why I'm doing some experiments using step-up regulator options, to try to extract as much as possible from the Alkaline AAs even if it cost extra 1uA or 2uA during the sleep. But at the end I'm getting a stable 3.3V all the way down to 0.8V on a single cell (I hope, as the tests still running).
I would opt for Lithium AAs rather than Alkaline and a voltage converter as you'll get useful voltage to the end of life without conversion inefficiency and much better low temperature performance.

Tom