Powering mote 24/7 using only a supercap and solar
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@gohan seen those for 15 USD/10 and for 6USD/5
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You are right @Ed1500, I receive so many shipments from AliExpress that now the postman is fed up with puting non-delivery notices in my mailbox, now he leaves the packages at the management office of my building, where they advance the tax for me when needed
@NeverDie yes I have some local shops, with very cheap delivery options, less than 1$ a;nd delivered the next day when they have stock. But unfortunately the inventory is pretty limited, I use them when the price difference is not worth the wait from AliExpress.
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@gohan yes, saw those. please keep us informed abt yr experience with those
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@NeverDie Oh dont worry, plenty of local online shops here for electronic components plus distributors for adafruit and similar.
However, I can order in china and have it delivered to my door often for less money than just the gas would cost me to drive to a local store, or to have it delivered from a local webstore.
The only thing is that sometimes I have to wait 2-3-4 weeks
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These look quite inexpensive:
https://www.aliexpress.com/item/30-x-ultra-capacitor-2-7v3f/32570929215.html?spm=2114.10010108.1000023.15.qq5cZ7
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@NeverDie indeed. but 2.7 Volt is a just a bit of a difficult value to work with and putting them in series makes the capacity drop, but I think one could run the attiny 13-25-45-85 from 1.8V so that might be a good combo
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Or, maybe this then:
https://www.aliexpress.com/item/Universal-Capacitors-Ultracapacitors-2-7V10F-super-capacitor-10F-2-7V-low-ESR-fast-charging-small-power/32688216790.html?spm=2114.10010108.1000013.4.G3WV1v&traffic_analysisId=recommend_2088_2_81019_new2&scm=1007.13339.81019.0&pvid=1ecf1af6-9158-4f9f-99ff-acaa16690ce2&tpp=1
It's just a wild card as to whether they actually perform according to the advertised specs, though. That's why I think it's helpful if we all share what we're actually using, and whether it meets expectations or not.
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@Ed1500 said in Powering mote 24/7 using only a supercap and solar:
@NeverDie indeed. but 2.7 Volt is a just a bit of a difficult value to work with and putting them in series makes the capacity drop, but I think one could run the attiny 13-25-45-85 from 1.8V so that might be a good combo
Yeah, and the RFM69--which is what I use--runs as low as 1.8v as well, so it's possibly a good match.
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@NeverDie 10F now we are talking. But yes I very well understood yr request to share experience. I acn only say thet the 1.5 F's i had performed well and with an RC network thrown together, they seemed in the right ballparc... but apparently seller now sells 1F and I cant vouch for those
The supercap is still a very viable alternative for smaller devices, so I will probably buy more in future and thus interested in which ones are good or not
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@NeverDie ah yes it does, but the RFM is usually connected to a microcontroller
So that is limited choice
i wonder if 1.8 Volt would seriously affect the range of the RFM69 (running mine from 3.3)
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Maybe a small booster to 3.3v could be used, since power efficiency shouldn't be a huge deal since the you will have the panel charging most of the time
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@Ed1500 said in Powering mote 24/7 using only a supercap and solar:
@NeverDie ah yes it does, but the RFM is usually connected to a microcontroller
So that is limited choice
i wonder if 1.8 Volt would seriously affect the range of the RFM69 (running mine from 3.3)Interestingly enough, the lower voltage doesn't seem to affect the range.
ATmega328p's can run at 1.8v also. In theory it should be set to run at 4mhz, but neither I nor anyone I know of has had problems running at 8Mhz down to 1.8v. If you run with BOD off and internal 8Mhz resonator, it only consumes about 150na while sleeping. That's why I haven't bothered going to ATtiny's. Maybe there are other reasons to do so though?
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So, I just ordered this:
https://www.aliexpress.com/item/3PCS-fala-capacitor-2-7v10f-super-capacitor-high-current-Low-ESR-fast-delivery-2-7V10F-ultra/32715563451.html?spm=2114.13010608.0.0.qFbHqn
and this:
https://www.aliexpress.com/item/CNIKESIN-2PCS-Fala-Capacitor-2-7v10F-Super-Capacitor-High-Current-Low-ESR-Fast-Delivery-2-7V10F/32804681189.html?spm=2114.13010608.0.0.qFbHqnfrom the same seller that gohan used. It's a risk, but if either of them check out, I may buy more of that brand.
I'll make a posting after I receive them to say whether they seem to be good or not.
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I recently purchased one of these:
https://www.aliexpress.com/item/Mega328-Transistor-Tester-Diode-Triode-Capacitance-ESR-Meter-MOS-PNP-NPN-M328/32685741297.html?spm=2114.01010208.3.92.KtC8xSand, for the price, it seems to do a decent job of measuring capacitance and ESR.
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@NeverDie I have used Attiny's mainly for their size. Pricewise, compared to a pro mini clone it is a bit foolish, unless you use the smd versions.
I had an attiny+ 433Mhz transmitter built in one of those garden lamps with a moisture sensor at the base where it sticks in the soil. Worked well, Not ideal, but it was nice to play around with
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@NeverDie interesting. May get one too
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@Ed1500 I got the bigger brother of that one. Look at the workshop discussion. I can't wait to start testing this stuff with all the voltage regulators I got and see how much energy I can actually store in the same 2 caps both in series and parallel
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@gohan keep us updated
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@gohan said in Powering mote 24/7 using only a supercap and solar:
Look at the workshop discussion.
Uh, what workshop discussion would that be?
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@gohan said in Powering mote 24/7 using only a supercap and solar:
Well, after much digging, I think I finally found your post. Is this what you're referring to?
Is it better than the one I posted?
I'm thinking of possibly getting one of these:
http://www.ebay.com/itm/261114892135
if only because the company that makes it also makes a popular low budget signal generator.I don't know that I actually need it though, except to verify that stuff purchased from Aliexpress actually is what it purports to be.
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Actually I went for the 2017 version on aliexpress that also has a pulse generator
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If anyone interested for some ideas of supercaps protection https://youtu.be/NsTAyD2i3rc
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@gohan said in Powering mote 24/7 using only a supercap and solar:
If anyone interested for some ideas of supercaps protection https://youtu.be/NsTAyD2i3rc
Useful video if connecting capacitors in series. If using just one capacitor, though, I wonder whether there's any advantage to using the described shunt regulator circuit compared to simply using a 2.7v LDO voltage regulator?
By the way, if your supercap's will be in a higher than room temperature environment, you may have to de-rate their max voltage. In general, supercaps won't last as long at high temperatures. Worth checking the datasheet for the details if that's a possible concern.
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I'll experiment when I'll get the small adjustable dc-dc converters and see how they go.
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@NeverDie The unforgettable "guy with the swiss accent" videos
Though very useful information, not so applicable to me as I am using 5,5V capacitors on a regulated 3V3 line
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I think the Swiss guy presents an interesting notion, and it's worth watching for that. However, I think his part choice of the TL431 is a poor fit for my solar application. According to the datasheet (cf page 6 of http://www.ti.com/lit/ds/symlink/tl431a.pdf), the minimum cathod current required for regulation is between 0.4ma and 1ma. From indoors, that's generally more current than I'm receiving from the solar panel! Now, double that, because you'll need two of them.
Also, it can't handle very high currents either, which is, I presume, why the Swiss guy resorts to the transistorized circuit and/or the chinese supercap protector PCB circuit.
HOWEVER, I notice that TI has a more recent successor to the TL431, called the ATL431, which appears to address both of those shortcomings: http://www.ti.com/lit/ds/symlink/atl431.pdf
Also, the ATL431 price would be much less than the Chinese transistor supercap protector board. The ATL431 price is about 58 cents, quantity 1 (http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=229180358&uq=636316574771858018)
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@NeverDie Oh that is good to know, thanks
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Has anyone seen this solution for balancing the supercaps?
Active Balancing Supercapacitors With SAB Mosfets – 06:12
— Mad Electron Engineering
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@gohan
Sounds better than the Andreas Speiss method. Thanks for posting it!
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Has anyone figured out how to do use this chip?
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@gohan said in Powering mote 24/7 using only a supercap and solar:
Has anyone figured out how to do use this chip?
I haven't pursued it, because I haven't heard a strong argument as to why two or more supercaps are better than one for powering a mote. The economics of supercaps seems to favor a one supercap solution.
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Well it is all related to what voltage you need to store I'd say: if you need to use more than the standard 2.7v you need more caps in series (for example if you want to make a 12v pack for your car)
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@gohan
Well, if you need more than 400F... maybe then. I'm sure there's a crossover point somwhere if the storage requirements get high enough. At that point, though, it would seem you're doing much more than powering a sensor mote.Anyhow, I look forward to seeing what you come up with. Maybe you've found an interesting use-case that I haven't even considered.
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not for near future... I am still preparing a bunch of other things
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I notice Julian Ilett seems to enjoy playing around with these 700F supercapacitors:
Julian's Postbag: #99 - SuperCapacitors and Computer Chips – 17:13
— Julian IlettEbay seems to have the lowest price: https://www.ebay.com/itm/1pcs-2-5V-700F-Automobile-Super-Farad-Capacitance-NEW-L85/262714791208?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
Anyone here tried them? I'm curious as to their self-discharge rate when they're not being charged.
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Also, although I'm doubtful about the brand, these 500F supercaps might be interesting because they're relatively inexpensive:
https://www.aliexpress.com/item/1PCS-AMS1117-5-0-DC-DC-Step-Down-Voltage-Regulator-Adapter-Convertor/32328707306.html?spm=a2g0s.13010208.99999999.269.QVr0W1
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so far what I saw is that good branded supercaps have much better self discharge compared to the cheap ones
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Am noticing that on Aliexpress you can now get an entire LTC3558 board for about the same price as just the ltc3558 chip on digikey.
https://www.aliexpress.com/item/GY-LTC3588-LTC3588-Energy-Harvester-Breakout-LTC-3588-Energy-Harvest-Collector/32755828984.html?spm=a2g0s.13010208.99999999.277.HJ7HHPSo, for low light energy harvesting, it might be interesting.
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@neverdie I think the size is a killer for me. I watched Julian's video and also remember this one:
Using capacitors instead of a car battery for 3 years and counting! – 06:57
— CatrinisinGreat caps and the price is really good too.
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@alexsh1 I purchased one of the 700F supercaps after my prior post just to see, and sure enough it has a pretty terrible self-discharge rate: about 0.4-5v per day. With a boost converter, maybe it would be good for powering an LED garden light at night.... Not sure what else it might be good for.
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@neverdie That's really bad - 0.5V a day. Questionable quality I guess?
I can see that similar capacitor AVX branded is much more expensive:http://uk.farnell.com/avx/sccy1kb707plble/super-cap-700f-2-7v-weldable-pin/dp/2856928?st=700F
Prices are coming down gradually. I suppose soon enough we may see AVX priced more affordably.
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Cypress Semiconductor has an interesting energy harvesting chip intended for wireless nodes:
http://www.cypress.com/file/219311/download
The chip looks a little easier to solder than some of them.
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@neverdie said in Powering mote 24/7 using only a supercap and solar:
I notice Julian Ilett seems to enjoy playing around with these 700F supercapacitors:
Julian's Postbag: #99 - SuperCapacitors and Computer Chips – 17:13
— Julian IlettEbay seems to have the lowest price: https://www.ebay.com/itm/1pcs-2-5V-700F-Automobile-Super-Farad-Capacitance-NEW-L85/262714791208?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
Anyone here tried them? I'm curious as to their self-discharge rate when they're not being charged.I charged up this supercap 5 months ago and then set it aside. Checking it now, it still has 0.6v left on it. I thought it would be at zero! So, maybe it really did hold a useful charge for much longer than I thought....(?)
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On the cheap supercaps I have they hold the 0.6v, they don't go to zero
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@gohan said in Powering mote 24/7 using only a supercap and solar:
On the cheap supercaps I have they hold the 0.6v, they don't go to zero
Interesting. So, if we were to put a few high Farad garbage Chinese capacitors in series, using a balance circuit, such that each just holds 0.6v, then I guess we could actually hold a meaningful charge for a very long time? Then, using my new efficient boost converter, we could drain most of the energy out of them:
https://www.openhardware.io/view/628/Efficient-Low-Current-Boost-Converter
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Apparently the answer is yes:
My 6 series 2.7V 500F supercapacitors w protection board for 16.2V 83.333F unit – 03:16
— electronzapdotcomIt also nicely illustrates that what's really needed is charge balancing across supercaps, not merely overcharging protection. Otherwise you are much more limited by the weakest supercap in the series chain of supercaps.
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what I meant is that they don't actually go to 0v even if you short them as you will always be able to measure some small voltage. I am no expert but my bet is that that 0.5/0.6v is kind of their bottom line where they don't hold any more useful energy below that.
For balancing there are SAB Mosfets that help to keep all the supercaps on the same voltage, but the reverse charge issue is the same for all series circuits, also LiPo worn out batteries can get to 0V and then getting reverse charged with all the consequent risk of fire.
