Not sure if others would have interest in this, but I'm designing a PCB for an easy-to-solder TH node. As presently conceived, it would have 3 surface mount components (an LED on the front and a resistor and capacitor on the back), plus a DIP atmega328p, a header to accept an inexpensive si7021 TH breakout board, an FTDI header, and an RFM69HW. The idea is that it would run at 8Mhz and be powered by two AA batteries, so it's sized to be compact but still easy to solder. The same thing could be achieved with wires and some of the other boards out there, but this might be a little tidier if a TH mote is what you want as either the starting point or the end-point.

PCB dimensions are 0.65x2.55 inches. i.e. it is narrower than a typical AA battery holder, but roughly the same length.

The LED and resistor are optional, and you could forego the capacitor as well if you wanted a truly bare bones TH solution. However, the pads are there if you wanted to utilize them. Also, you could skip the si7021 BoB if you wanted just a generic mote.

I had hoped that someone would make an easy to solder board like this for the RFM69HW, but I got tired of waiting and finally decided to just make my own.

I found a good place to do range testing.... too bad I didn't bring the gear!

@OldSurferDude If I have a question about something I generally post the question. Sometimes someone will answer it, and all is good. But on those occasions where no one answers it to my satisfaction, and I later do figure it out myself, then I return and post the answer to my own question. I think if everyone followed this protocol, it would help. What I see across forums (not just mysensors, but just about all forums everywhere) is people who post questions with a "Thanks in Advance" attitude, but who never bother to close the loop if they do find the answer. Or they never confirm whether or not someone's suggestion worked or didn't work. The result is that when searching for an answer, one has to search through a lot of posts which don't contain any useful answers. So, I would encourage everyone to return and post answers to their own questions, if no one else already has, because in all likelihood someone else will have the same question in the future. I think that one small change might make a huge difference.

Good news! Last night I did some accelerated load testing on the supercap. First I charged it to 3.6v and then I hooked up an RFM69HW mote which woke up once a second to do 3 things: 1. check the voltage level, 2. turn on an LED for 1ms to simulate a sensor load, and 3. transmit a packet containing the voltage data using the RFM69HW.. Bottom line: 14,111 packets transmitted before running out of juice.

Not bad for a first attempt.

Yesterday received the PCB. Today assembled for testing this battery-powered nRF52-based passive infrared motion detector:

Made this 12 button keypad. Requires only one analog pin to read which button is pressed, and any button press can also wake an arduino from sleep:

Consumes no power when no button is pressed.

For sure, the store shelves are pretty much overflowing with smart home products and IoT these days, much more than in the past. Is it just diffusion of attention, or do people just buy what they need now in complete systems or something? Or buy stuff that has phone apps instead of a hub? Or has Home Assistant taken over? Or Amazon Alexa? Not much in the way of new postings compared to the past. If anything, I thought there'd be more activity due to more and more IoT interest generally. If anything, it seems like Mysensors has a more robust and complete system now than in years past, and it's broad enough to include just about everything. What gives? Have off the shelf prices dropped so far that the economics no longer favor rolling-your-own or something? i.e. buy rather than build? Where's the new frontier? Is it now AI and system level stuff? I'm really curious. I mean, not all that long ago Google bought a thermostat company (Nest) for over a billion dollars. There's clearly been a sea change, and I'm just wondering what changed.

A pair of lithium AA primaries is hard to beat because:

1. Unlike alkaline's, they don't leak.
2. Have a look at the discharge curve: https://data.energizer.com/pdfs/l91.pdf By the time they drop to 2.4v, if not before, you'll want to replace them.
3. Obviously much longer life, both shelf life (20 years!) and energy capacity.

I think running 8Mhz from the internal RC is a no-brainer: wake up time is less than 4us. So, if your node wakes up often, you'll save a ton of energy over time.

The best time to take your battery measurement is immediately after a Tx. That will give you the most conservative reading. Save that measurement in a variable and then send it in your next transmission. Switch on your ADC just before Tx and take your first ADC measurement during Tx, because you have to throw out the first measurement anyway. That way you can take a fresh (and valid) ADC measurement just after Tx before the voltage rebounds.

Hope that helps!

Here's the version that I most recently assembled:

As you can see, the 15F supercap is now on the board itself. It works fine.

I've since made a few refinements and have sent the new files off to be fabbed. The newest version of the PCB will measure roughly 22mm x 22mm.

Reporting back: I have my BambuLab X1C printer setup and have printed with it for about a week. It's fantastic: it's fast, and the prints come out perfectly every time. Truly an appliance: it works with only minor setup straight out of the box. I'd say it's a quantum leap better than my Prusa MK3S, which I guess I should try to sell while it still has value.

I would think that it's the ambient air temperature that affects how much condensate you collect, together with how much fuel was burned. After the initial warm-up that gets you to steady state, wouldn't the efficiency be constant?

If the acidity is a problem, you can run the condensate over a bed of acid neutralizing rocks before it goes down your main drain. It's a thing.

Some kind of through-beam sensor might work: https://www.amazon.com/Optical-Endstop-Photoelectric-Control-Printer/dp/B07MFT8NWJ/ref=asc_df_B07MFT8NWJ/?tag=hyprod-20&linkCode=df0&hvadid=241938907421&hvpos=&hvnetw=g&hvrand=9189408107204898573&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9028292&hvtargid=pla-664653941028&th=1

I once was interested in the same sort of thing for monitoring the effluent from a reverse osmosis filter at the air-gap to confirm that it wasn't wasting a lot of water. In my case there turned out to be an easier way.

If it drips slow enough, maybe a simple photocell and led could be used to count each drip as it drops in-between. Use arduino analog input to look for a drop in the light intensity. i.e. a simple electric eye.

@gregvp said in Fork of BigClive AA Battery Trickle Charger:

I have a project on my list to make a NiMH capacity tester using as the load a boost regulator loaded with a range of resistors. But at my current rate of progress through the list, I'll be dead first.

Luckily, if you want to do some testing before you die, you can get pretty decent load testers for cheap these days. Not sure how accurate they are in an absolute sense, or how accurate you would need them to be for your particular purposes, but for anything I do they seem "good enough" and provide repeatable capacity numbers.

https://www.aliexpress.us/item/2255800047204598.html?spm=a2g0o.productlist.0.0.1e963f191wOpcX&algo_pvid=8930e84c-2b17-4afd-9458-68d1aabbc9bc&algo_exp_id=8930e84c-2b17-4afd-9458-68d1aabbc9bc-20&pdp_ext_f={"sku_id"%3A"10000000947167753"}&pdp_npi=2%40dis!USD!13.43!9.67!!!!!%402101d8b516678388477845208e191c!10000000947167753!sea&curPageLogUid=kEzSSWx2qqOU

I agree with your comments regarding the likely use of niMH batteries. Not sure what load to pick, but I do need to pick some kind of reference load--maybe 1C?--so that I have some way of gauging whether or not the cells kept 24/7 in the forked BigClive trickle charger degrade noticeably more than cells which aren't. In the end I suspect Calendar aging will be the biggest effect, but I won't know for sure unless I run the experiment.

@mfalkvidd As near as I can tell, there's is commonly a conflation of ideas that really should be separated. According to Dave Jones here:
EEVblog #515 - Battery Ionic Resistance Investigation – 27:52
— EEVblog

internal resistance (at least in the case of a 9v battery) 1. is quite small, and 2. doesn't vary much if at all over the life of the battery. Apparently it is what's measured with the 1kHz signal. However, what is much larger than that is what he calls "ionic resistance", which has to be measured under load. So..... I'm not sure which of those two, or what mix of those two, the battery charger is measuring. I've tried two alternate battery chargers for measuring "IR", but they each appears to measure different numbers.

The number I rely on the most is usuable mah in a battery that's arrived at by a constant current discharge, and I use an OPUS BT-C3400 to measure that. Its a repeatable number, and it's definitely a useful number. However, I'm unsure as to what value the "IR" number has, but I'm collecting it anyway in case I/we eventually figure it out, or else figure out how to measure it in a way where it has actual usefulness. So far it seems like "ionic resistance" is the more useful concept, because it indicates how much the voltage drops under a particular current load, and, anecdotally, that voltage drop does seem to be less when a battery is new or almost new as compared to when it is older and closer to failing.

Plainly, the voltage drop is greater the greater the current draw, so I'm developing skepticism that there really is a single number that represents battery health in that regard. Perhaps the only number that matters is the voltage drop that a particular application experiences from the current that it happens to draw? At the moment, I'm leaning toward that hypothesis. i.e. there is no single context free number that has meaning. Instead, maybe pick your own test conditions that have meaning for your particular application, and measure that instead. Not entirely sure though. Everybody knows that you should measure battery voltage under load, but exactly what load and for how long it should be applied before taking the voltage measurement..... I'm not aware of any standards in that regard.

Actually, the closest thing I've found to answering this question comes from putting LiFePO4 batteries under high load and seeing how they respond:
The Final Word On Grade B - Lifepo4 cells Grade A vs Grade B - SFK – 33:33
— Sun Fun Kits LLC

In that video a guy who claims to have tested thousands of LiFePO4 batteries claims it to be the method he uses to separate "Grade A" cells from "Grade B" and below cells. First he fully charges the battery, then he hits it with a 100a to 200+a load to see how it reacts. If the voltage in a cell then sags below 3.2v during that load test, then according to him it's not a "Grade A" cell. He also looks at how quickly a cell "snaps back" to inits initial voltage after the loading stops. My point is: he's looking at battery dynamics; he's not measuring a single number to determine how "good" a cell is. On the other hand, I would imagine that any sort of dynamic could be reduced to a number using mathematics....

So.... that's how a pro does it. Unfortunately, his method is more like a comparison of battery dynamics, centered around what is EVE certified as "Grade A" rather than arriving at a single hard number, but even so it's an enlightening youtube video--better than the meandering eevblog youtube video IMHO.

I suppose I could come up with a similar test for NiMH batteries, but it would be derived from a similar method of making dynamic comparisons against "known good" high quality Eneloop cells rather than referencing a single IR hard number spit out by a battery charger. That is.... unless someone here has a better way. If so, please post!

@mfalkvidd Presently, I'm just reading the IR value off the charger (see photo above), on the assumption that whoever designed it knew what they were doing (not always a good assumption). For instance, in the above photo you can see that it is reporting 72millohm on the cell in position #8 (the rightmost cell). By changing the slot selection, I'm able to read the millohm measurements off of each of the other cells in slots 1 to 7 as well.

Reporting back:

I purchased brand new Amazon Basics that I'll use to trial this charger:

I'll be recording both their internal resistance and capacity prior to the start of the test, and then measure them again somewhere down the road to see how they do or don't degrade relative to a control group of cells from the very same batch of brand new Amazon Basics NiMH rechargeable batteries. Not sure how long will be long enough to trial this method of charging. Any suggestions? Otherwise, I'll just re-test them whenever the spirit moves me to do so and report back at that time.

I understand that BigClive meant for this to be a simple design and a simple project, but depending on how the trial goes a a refinement might simply be to insert a circuit which charges them for, say, an hour or two each day rather than charge them continuously. Of course, you can easily buy off-the-shelf timers to accomplish that already, so that might be another way to arrive at an equivalent solution without needing to make any changes to the circuit board.

Anyhow, I rather do like the idea of having fully charged AA batteries always available.

Is battery internal resistance a meaningful measurement? I ask because I have yet to find a battery charger that measures internal resistance in a repeatable way. Is there a better, more repeatable wayt to measure it? As you can see from my markings in the photo above, the reporting internal resistance on each of gthe batteries is already all over the map, with a low of 52milliohm and a high of 90milliohm.

@mfalkvidd If things go sideways in the "you know where" region of eastern Europe, such that they affect Sweden, feel free to open a thread and ask for help. I'm sure everyone on this forum will do their best to get you any information or other resources you might need to adapt to events as they develop.

This youtube is perhaps a little tangential, but I found it both informative and entertaining to watch. It makes an argument for why you'd want to have a stand-alone GPS (no, not the usual "connected" one in your phone) for use in emergency scenarios:
Why Everyone Needs a GPS – 27:34
— T.REX ARMS

This youtuber also has a great sense of humor and demos some interesting products.

FWIW, the Red Cross recommends everyone should have paper maps as a backup, but these days who keeps up-to-date paper maps anymore? What this youtuber describes might make more sense as an alternative to paper maps, and he gives a compare/contrast as to why.

Although he didn't cover it, I'm fairly sure there's a way to download google maps to your phone so that you can be stand-alone that way, and this method wouldn't require any added expense (provided you have enough spare storage in your phone).

The same guy also did an interesting overview of emergency radio communications, which is very much on-topic for this thread:
An Introduction to Radios and Emergency Communication – 21:25
— T.REX ARMS