Hi All, esp Felix!!
Felix - any thoughts on creating a micro moteino. There have been lost of great examples recently and I am sure there is a market!
Hi gregcope,
I think you may refer to the Tino (https://lowpowerlab.com/forum/index.php/topic,1269.0.html) created by forum user joelucid, I don't really want to steal his idea and go do my own thing based on that. Unless he wants some kind of collaboration.
When you say micro, what defines a micro node other than size?
Yes - was referring to the Tino and others.
I choose "Micro" as a generic term for "little"
I think the main thing that defines a "micro" is coin cell sized. Could be coin cell or Lipo, but just that Penny sized "thing" and probably only a few GPIO pins exposed.
Not wishing to step on any toes, and I appreciate your concern, however people are making these due to a gap in the market.
Just an idea.
I will let joelucid respond and share his thoughts here about that possibility or his vision of Tino.
I think it's a credit to Felix for designing the current Moteino platform and supporting it in a way that encourages others to develop their own creations. Collectively, we all benefit when one person builds on another's work.
Congrats to both Felix and joelucid. There is room and specific applications for everyone.
QuoteI will let joelucid respond and share his thoughts here about that possibility or his vision of Tino.
Sorry - I missed this. Here's the Tino thread for reference: https://lowpowerlab.com/forum/index.php/topic,1269.0.html
I think there are two important use cases for these Tino style boards: long term coin cell operation or energy harvesting for infinite battery life (with Lipo or supercap). I'm not really interested in Lipo by itself because of the high self discharge rate.
Essential for any micro-board is a wireless bootloader: you just cannot use optiboot to upload a sketch because it's not coin cell optimized. The wireless bootloader is also essential so that no headers need to be attached (or heaven forbid pogo jigs be created). And there is just no space for an extra flash chip to support Moteino style OTA updates. See https://lowpowerlab.com/forum/index.php/topic,982.0.html
If you just create a normal arduino app for these nodes you will quickly sit with a dead battery and/or a radio trying to send/receive forever. A lot of additional software is required to enable writing really energy efficient code. E.g:
- Effective sleep code
- Modified RFM69 library
- Listen mode (see https://lowpowerlab.com/forum/index.php/topic,982.0.html)
- Low voltage recovery (sleeping radio and recovering VCC when voltage crashes)
- Minimum voltage reporting for each wake pulse
- Wake pulse length reporting
My vision for Tino is to provide all of this software together with the HW to have a really great out of the box experience: Just unpack your Tino (coin cell already soldered on), attach a separate USB wireless programming adapter to your laptop, compile a sketch using the Arduino IDE, upload wirelessly and run.
HW wise I want to make a couple of additions:
- A RTC or a HW watchdog timer (will reduce power consumption by another order of magnitude).
- And I'm hoping to add some circuitry that will add a fully programmable boost converter to the board to support higher voltage applications (I need this for a sprinkler controller and for a PIR sensor).
The boost converter would be implemented using the 328p to avoid another chip. It would not generally power the Tino or the radio itself to avoid efficiency losses. But it would support powering higher power circuits by charging a cap in short bursts over an extended period of time and the pulsing the joules into the circuit during short wake periods.
If I can fit these components it likely means only one contact header for expansion.
In the end Tino should be usable for most battery use cases (considering coin cells come in up to 1000mAh :) ). And it will likely be the most power efficient Arduino clone on the market today.
I really have been doing all this just for fun for myself. But I have to say it's so much fun working with Tinos I've been thinking sporadically about making them available to others. I also think there's a lot of misunderstanding in the market wrt coin cells - so many people think what Tom and I have been doing is just not possible.
One of my constraints is that I don't want to manufacture the HW myself - I have way too many left hands for that ;). So I'd have to partner with someone for that piece.
So what do you say? Is this interesting? Would you want one? Am I missing anything important?
Joe
QuoteOne of my constraints is that I don't want to manufacture the HW myself - I have way too many left hands for that ;). So I'd have to partner with someone for that piece.
Felix might be able to help?
QuoteSo what do you say? Is this interesting? Would you want one? Am I missing anything important?
I think there would be allot of interest (for a given value of allot in this space).
Ok, I measure some cautious interest.
QuoteFelix might be able to help?
Not sure if this is a really good fit for Felix manufacturing operation. It's certainly seems too early to seriously consider. And selling small self produced batches is not really interesting from my perspective as I have said.
I think I'll just keep on going, letting fun dictate the direction. If something comes together that might appeal to a larger audience I might start a kickstarter campaign to gauge interest in the larger community. There is significant work that would be required to make Tino and the software around it foolproof - and it only makes sense for me to do that if that interest is measurably there in reasonable size.
QuoteI think it's a credit to Felix for designing the current Moteino platform and supporting it in a way that encourages others to develop their own creations. Collectively, we all benefit when one person builds on another's work.
I have to strongly agree with that. Moteino really hits a sweet spot. Thank you Felix!
Joe
Thanks guys for your thoughts.
One particular aspect of my "manufacturing operation" is that I need to keep it as simple and optimized as possible. I cannot spend too much time on a single unit of anything I make. It has to be "designed to manufacture" as often the term is thrown around by the industry. I look at the tiny coin cell nodes as even more artisan creations because they would require quite a bit more manual attention (it looks like).
I am optimized to assemble and test lots of boards in a short amount of time. Hand assembly is where I don't have a lot of capacity, hence part of the reason I sell kits and not ready made products. One of the most significant time burners is soldering the radios to the Moteinos and loading them with test sketches, that probably takes double the time to assemble the board (less reflowing which is a fixed amount of time but only requires me to drop a panel in the oven).
Hi Felix,
Big picture is clear. However a couple of questions / comments:
Quotebecause they would require quite a bit more manual attention
In what regard other than support do you think would they require more attention? I know I'm having trouble making them without bridges, but I've so far attributed that to my little experience with reflow. Do you think these problems come necessarily with the small size?
QuoteOne of the most significant time burners is [...] loading them with test sketches
Now at least for the test part you could probably save time using the wireless bootloader.
Joe,
Re small pitch/bridges - yes & no. It depends on design, stencils, reflow profile etc.
You have to burn a bootloader and fuses to the atmega and that has to be easy and fast. Then you have to solder the RFM radio, and on top of it the battery holder. That is quite a bit of work, what if someone wants 200 units in 2 days, can you do that? It's a question you have to be prepared to answer. So all is assembled before you have a chance to properly test and see if anything fails, and if so the unit is basically scrap. To reduce that to a minimum you have to have a great design and a great assembly and test procedure.
I think it's related to the subject. I've never used any of their products, but this thread hints at something that should already available and as low power alternative, directly targeted at battety operation, and looks very interesting. Till now, since a year already, it's all promises and no delivery, sadly. Here. (http://forum.anarduino.com/posts/list/15.page)
Interesting Kobuki, thanks for the pointer. They also use an RTC to get sleep power very low. However the modules with 3.3V LDO regulator are hardly coin cell compatible.
Actually the combination of 3.3V LDO, supercap and radio module looks very weird to me. If it runs with coin cells there must be no 3.3V LDO. If this is optimized for batteries other than coin cells why add a supercap? If the battery is empty and you have a radio module the server can just send a new stamp when the node had its battery replaced.
Yeah, dunno about the supercap either. Maybe the LDO is there to allow adding components with more stringent power requirements?
It's not exactly "micro", but when it's going to be available finally, it should rock as a battery-operated, ultra low-power device (https://hallard.me/category/ulpnode). It might be interesting in your pursuit for a better LP node - all design choices are documented, bootloader and other code is available, so might be useful to gather ideas. The node itself in its current form looks like a xmas tree with all the bells and whistles (even a Groove socket is included), but that should make life easier for beginners or users that only wish to have a customised remote node for anything.
Only unfortunately the core idea is based on a misunderstanding of ohms law:
https://lowpowerlab.com/forum/index.php/topic,1269.msg8530.html#msg8530
Hmm, but he does use a cap for storing power... See here (https://hallard.me/ulpnode-low-power-secret).
Quote from: kobuki on September 15, 2015, 07:01:21 PM
Hmm, but he does use a cap for storing power... See here (https://hallard.me/ulpnode-low-power-secret).
The cap is only there for sleep, it's pretty small. I think it's a combination of a wake-up device plus sleep power provider. The piece I would implement in Tino by using a ultra low power HW watchdog timer.
Some more thoughts on the effectiveness of the booster:
Obviously at best Vout * Iout = Vin * Iin because of conservation of energy. Therefore Vout/Vin = Iin/Iout and every increase in Vout needs to be paid for by increasing Iin. Now when the internal resistance RI of the battery is low that's no problem. However when it is large the increased current will reduce Vin, working against the booster. So for a given RI where's the sweet spot? Let's call the coin cell open voltage Vbat and equivalent input resistance of the booster Rin.
Then Vin = Vbat * Rin / (RI + Rin) and Iin = Vbat / (RI + Rin). For a given Rin we extract a power of Vin * Iin from the battery which becomes:
Vbat * Rin / (RI + Rin) * Vbat / (RI + Rin) = Vbat^2 * Rin / (RI + Rin)^2
The derivative is
- Vbat^2 ( Rin - RI ) / (Rin + RI)^3.
It has a root at Rin = RI. Therefore you extract the maximum power from the coin cell at an Rin that's equal to the internal resistance. You can then decide how to transform that power - btw, converting it to 3.6V is hardly going to prolong the lifetime because 328p/radio use more power than at lower voltages.
At first that seems to imply that as long as Vin doesn't break down to around 1.5V without the booster you could still get some gains using it. But graph the extracted power at http://www.derivative-calculator.net/#expr=b%5E2x%2F%28a%2Bx%29%2A1%2F%28a%2Bx%29 and you'll see how flat it is around it's maximum. I don't see this even compensating for the booster efficiency losses.
All this is consistent with the fact that ultra low average pulsed loads can extract close to, if not more than, nominal capacity from a coin cell (see the listen mode thread for sources).
In the end you want to provide a platform with as little conversion losses as possible (including booster and cap charging losses), run it at as low a voltage as possible and support developers in writing code that creates the shortest possible pulses and the lowest average loads.
Of course a booster does make sense for certain scenarios (I want to include one using the 328p). I'm looking at 1) providing a larger voltage at low power (scenario PIR sensor) and 2) providing high power pulses by precharging a cap (sprinkler controller). But powering the radio and the 328p using it is a step back in efficiency.
Joe
The author of the blog has already spent a year refining his designs. While your calculations are probably correct, I doubt he's some fool experimenting for naught for a year. I especially like the idea of being able to use a single, common AA cell for operation. You both have different design ideas but only time will tell which one works better or at all. The solution in the blog can be further refined or fixed. Such as your own designs with Tino. Neither one is a finished, well tested, available product (vs. the Moteino, which already is). There are other projects that follow a similar design (using a boost converter), albeit without a cap AND have a pretty long battery life. Even many common battery-operated consumer devices do. They can suck a 1.5V cell down to 0.8V or less until they demand another set of batteries.
@Joe: reflecting to your latest edit. As a consumer, I only care about battery life (and price). If I'm not bothered with swapping batteries for like 1-1.5-2 years, then I think it's fine :) Whatever solution lies inside.
@kobuki,
I'm just trying to learn from these projects and incorporate the best ideas in my design. ULPNode has already convinced me to put a ultra low power HW watchdog on the Tino to at least match its sleep power consumption. Looking critically at all aspects from a coin cell perspective. Necessary for me, you can just pick up the final product as you say :-) - at least the ones that ship at some point.
Now this is also a sport - so 2 years battery life are unacceptable to me :-)
Oh yeah, btw, boost converters are great for single non coin cell operation.
Yeah, as a consumer, my needs are different. As an engineer, my interests are again different, although I'm no EE design expert guru at all (I have an SW engineer background instead), only a hobbyist wanting to learn. You might not be satisfied with 2 years "only", but is it worth the effort to achieve a lot more? I think in this case it's worth thinking about the "what is good enough?" approach :) You might be able to produce something that only last 2 years on this coin cell... But you already have a product then, ready to be refined. And the world doesn't stop, so we might see some new type of battery within 2 years, existing ones increasing in capacity while maintaining the same size, etc - so I'm not saying it will, but it at some point might become pointless, trying to achieve a significantly higher goal in the short term. Please just think of it as me thinking out loud, I'm not trying to argue with your aims. But I also expect the IoT world and thus battery-operated technological advances explode in the following years (well, explosion has already begun, in fact...)
BTW, should you ever start selling Tinos, expect me to be one of your first customers ;)
QuoteYou might not be satisfied with 2 years "only", but is it worth the effort to achieve a lot more? I think in this case it's worth thinking about the "what is good enough?" approach
Yeah - if it were only so easy once you've been bitten by the bug. I blame Tom for turning me on to this :D - but hey, I'm pretty sure I could stop if I wanted to ...
Quote from: joelucid on September 16, 2015, 09:40:05 AM
You might not be satisfied with 2 years "only", but is it worth the effort to achieve a lot more? I think in this case it's worth thinking about the "what i
Yeah - if it were only so easy once you've been bitten by the bug. I blame Tom for turning me on to this :D - but hey, I'm pretty sure I could stop if I wanted to ...
In the words of Etta James:
QuoteIt's a world full of trouble and a world full of pain,
I'll take the problem, but I won't take no blame.
:D
Tom
QuoteI doubt he's some fool experimenting for naught for a year.
I came back to this topic today as I wanted to check if an ultra low power voltage supervisor might be superior to the ULP watchdog timer I'm planning to use on my TinoV2. After all being able to get an interrupt on low voltage would be a nice feature on top of providing a regular wake signal.
After I couldn't find anything remotely interesting I checked what the ULPnode uses. Turns out it's the http://www.onsemi.com/PowerSolutions/product.do?id=NCP302 with a quiescent current of 500nA! That's more than my total energy budget for TinoV2 including 328p sleep current, WDT, measurement, radio sleep and TX.