💬 The Harvester: ultimate power supply for the Raybeacon DK
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@NeverDie Well, round shape has property of manhole cover - it can't fall through :-)
Another thing I'm thinking about is to get rid of CR2032 and build it on a 3rd party module and a supercapacitor. This way It can be much smaller, but number of other drawbacks may come. Smaller size usually means worse radio performance. Also, the smaller the board, the higher integration required thus severely impacting production cost. This especially may affect expansion modules which are usually a DIY thing.
@Mishka If you do decide to try for a smaller design, there exists a tiny (3.2mm x 2.5mm) 11mF supercap that's rated for 10,000+ charge cycles and that might perhaps be just barely enough capacity to do some minimum amount of work:
https://www.sii.co.jp/en/me/datasheets/micro-battery-2/cpm3225a/
or possibly one of the variants that the same company makes.
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Hi, i am actually building a similar PCB for Energy Harvesting with SPV1050. What about the 196 HVC ENYCAPâ„¢ from Vishay like MAL219691262E3? Seems for me as a good Super Cap with acceptable dimension...
@Sebastian-Walther said in 💬 The Harvester: ultimate power supply for the Raybeacon DK:
Hi, i am actually building a similar PCB for Energy Harvesting with SPV1050. What about the 196 HVC ENYCAPâ„¢ from Vishay like MAL219691262E3? Seems for me as a good Super Cap with acceptable dimension...
Dividing this into pro's and con's, one pro would be, as noted in the datasheet, "No cell balancing necessary."
Although you could work around the issue, one con would be that the ESR's look rather high, which could bite you especially hard if doing high power radio Tx's.
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@NeverDie Well, looks like that is the space mission panel :space_invader: :space_invader: :space_invader: Won't be cheap anyway. On the other hand recently I seen a lot of news about so called nighttime photovoltaic power, who knows how fast it can be delivered to market.
In a meanwhile, I had a chance to play with the Harvester board. Please don't consider everything below as any serious test or a comprehensive review - I just rather tried to understand how the modules are working and what can I get from them.
Following our prior discussion, I've assembled one board in buck-boost mode (the original PCB), and have tweaked another one to the boost configuration. The only solar panels I have are:
- IXYS KX0B25-02X8F. Single panel is annoyingly weak so I connected two of them in series.
- The SCNE SC-1338 from the test above.
- SORBO SB-3077. A big (79x40) panel from solar torch. Didn't tested it like the other two, but noticed about 6V from it.
For the load there is 1500µF 4V tantalum capacitor installed. V_uvp threshold has been set to 2.2V, and V_eoc to 3.2V. Please also note, the MPPT resistor values were set to V_oc=12V (which is too high for all the tested panels) and no adjustments were made to them for any of the tests.
Most of the tests I made in the evening at home where LED lights are the most common source. I used light sensor on my phone to measure light illuminance. Looks like it gives more or less sensible values; such, 50 lux corresponds to a dim light, 250 lux is an office light or indoors illuminance in cloudy day, 1000 lux is outdoors light in cloud day - similar values I've seen in tables over the Internet. After checking illuminance I placed solar panels in the same area and measured most important voltages:
- V_pv - PV panel voltage when it is under load (but see my comments)
- V_store - voltage at the spv1050 store capacitors (2x47µF)
- V_out - voltage on the output capacitor (1500µF)
For low light conditions I waited several minutes for the capacitors to charge and read values only when the system became saturated (or at least look so). Results and my notes are represented in the following table:
The spv1050 datasheet provides quite detailed description on how it works. The only interesting question was - what happens in buck-boost mode if the harvester cannot maintain V_store voltage anymore due to low illuminance. I found that store and the load will be connected as long as V_out>2.2V. After that, spv1050 will shut down the DC/DC and connect PV to the store. I think DC/DC was on because panel voltage raises up from 0.25V to 0.52V when the store disconnects from the load. Why is it 2.2V and not 2.6V as specified in the datasheet, I don't know.
Another interesting test was how much time it will require to charge the 1500µF capacitor to 3.2V. For that I tried different panels with both buck-boost and boost boards. Please note, since the boost board has 4V limit (due to the tantalum capacitor) and pair of the IXYSes are capable to produce up to 8V, I've skipped this couple. The results are in the table below:
You was absolutely right when expressed the concern on the SolarBit panels - they work much better in the sunlight. The SCNE seem also prefers full spectrum to my LEDs.
Evaluate whether this is a good or bad result is possible when considering the load itself. Accordingly to the Nordic, the nRF52840 will consume about 32µC
per heavyweight BLE event, for example, when running at 2.2V (lowest possible value for the spv1050) and sending +8dBm advertisements. For tiny packets it may be as low as 5µC.The tantalum capacitor stores 1500µF*3.2V = 4800µC - exactly this amount was delivered by the spv1050. This roughly equals to 150 advertisements, or 960 connection packets. If ignore other waste (like sleeping current) and assume 5 minutes as an average result on SCNE-alike panel (indoors, daylight), the system should be able to advertise once every two seconds or send small data packets once every 1/3 second without discharging a battery.
Of course, more light means more power, and there is the night too, but with proper panel and correct location I think it should be possible to maintain positive power balance.
So which configuration to prefer - boost or buck-boost? I still have no simple answer.
The boost is good when you're working in low-light conditions and can keep it low-voltage. I also have impression that the spv1050 is sensitive to the current it can get from a panel. Therefore a couple of single cell panels (i.e low voltage, high current) might be the right choice. On the other hand, it's risky to attach high voltage panels to the boost harvester - neither battery not capacitor will tolerate 6V.
The buck-boost configuration has no such drawback - any panel you may find on attic will very likely to work. Another advantage you might have noticed is that it delivers faster. When fast is fast enough - it depends. But in the low-light when it may took up to 30 minutes to charge a 1500µF capacitor the boost advantage is not so obvious.
@Mishka said in 💬 The Harvester: ultimate power supply for the Raybeacon DK:
Well, looks like that is the space mission panel
I found a place that sells these more exotic cells in quantity 1: https://www.solarmade.com/store/category/solar-cells
BTW, according to the news, the company that makes the highest efficiency solar cells (>30% efficiency) laid off its workforce in December, so who knows if those cells will ever be manufactured again.
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@Mishka said in 💬 The Harvester: ultimate power supply for the Raybeacon DK:
I'll be grateful if you will share your findings.
Yes, of course. I ordered it just today, so I'll update you after it arrives if I learn anything from it. I suspect the wiring issue you flagged may allow the width to be reduced but prevent the length from being shortened. Anyhow, if not this one, then probably some other solar cell exists that can be trimmed to fit after-the-fact--hopefully one with good efficiency!
As for the cypress solar beacon, it actually does a little more than just that: it broadcasts the temperature and humidity from a couple of onboard sensors. Nonetheless, Cypress describes it this way: "The Solar BLE Sensor is ultra-low power and works with just solar energy." ... and yet, isn't that a small battery I see on it? Maybe it's rechargeable, and cypress opted for that so as to save space as compared to a supercap? I haven't looked into it, but that's my guess.
I'd say they did a good job of squeezing it down to the size of quarter. It makes me wonder just how much smaller it could be made. Interestingly, even though the solar panel takes up a lot of board real estate, it's not much worse than a coin cell battery. So, if it could still run on a solar panel that's even smaller, then the whole thing could be shrunk even more, and then solar would be an even more tangible bonus than merely not needing to change batteries.
@NeverDie said in 💬 The Harvester: ultimate power supply for the Raybeacon DK:
... and yet, isn't that a small battery I see on it? Maybe it's rechargeable, and cypress opted for that so as to save space as compared to a supercap? I haven't looked into it, but that's my guess.
I think I may have found the part: https://www.digikey.com/product-detail/en/elna-america/DCK-3R3E224U-E/604-1007-ND/970168
The picture seems to match. So, not a battery after all, but rather a supercap (one with rather high ESR). Likely 220mF, or thereabouts. -
Powerfilm makes a thin film solar cell which they say is good for energy harvesting at 200 lux and less. According to their flyer, at 200 lux it says the expected power is 220uW for the panel included in their Nordic nRF52832 solar development kit. However, at 100 lux the expected power is not 110uW (which would have been my guess), but instead only "1,430uW"! (Even though it's a USA based company, I'm assuming they're using the European convention of a comma instead of a period for decimal notation)
https://www.powerfilmsolar.com/media/cms/Indoor_Solar_Development_Kit_with_N_A90DF4062ABC1.pdf
Since they're "official" datapoints, I thought it worth reporting, not for the absolute magnitudes (which presumably should be a function of panel size) but for the relative magnitudes. I'd be curious if other types of solar cells also degrade as quickly when going from 200 lux down to 100 lux or whether some manage to do a lot better in terms of energy made available for harvesting. If not, then without resorting to larger panels it sounds as though somewhere around 100 lux or higher is the practical limit for small footprint sensors.
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Looks good, I am wondering about the high power, cannot imagine :thinking_face: because meanwhile I tested the ECS300, used in Enocean products, also designed for low light (200 Lux) with amorphous crystalline cells. But the MPP is only about 160µW @ 1000(!) Lux.
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Looks good, I am wondering about the high power, cannot imagine :thinking_face: because meanwhile I tested the ECS300, used in Enocean products, also designed for low light (200 Lux) with amorphous crystalline cells. But the MPP is only about 160µW @ 1000(!) Lux.
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Looks good, I am wondering about the high power, cannot imagine :thinking_face: because meanwhile I tested the ECS300, used in Enocean products, also designed for low light (200 Lux) with amorphous crystalline cells. But the MPP is only about 160µW @ 1000(!) Lux.
@iiibelst said in 💬 The Harvester: ultimate power supply for the Raybeacon DK:
I am wondering about the high power, cannot imagine because meanwhile I tested the ECS300, used in Enocean products, also designed for low light (200 Lux) with amorphous crystalline cells. But the MPP is only about 160µW @ 1000(!) Lux.
I suspect it's primarily a size thing. The ECS300 is lower power at least in part because it's comparatively tiny: just 35mmx12.8mm and with a short-circuit current of 6.5ua at 200 lux.
https://media.digikey.com/PDF/Data Sheets/Enocean PDFs/ECS300_310.pdf
If only we knew the actual size of the PowerFilm panel used in the demo, then we'd be able to directly compare the relative efficiencies of the ECS300 against the powerfilm. Even so, there's likely to be a lot of slop in these numbers, because they are each probably doing their 200 lux measurements using different light spectra (i.e. whatever shows off their product in the most favorable light, so to speak). -
Regarding capacitor selection for the SPV1050 and nRF52. The undervoltage protection for the SPV1050 is 2.2V. At the same time, nRF52 works starting from 1.8V. The maximum allowed voltage drop should be no more than:
U_drop = 2.2V - 1.8V = 0.4V
Taking in account, that the nRF52840 can draw up to 25.8mA at 1.8V when transmitting at 8dBm, it means that supercap ESR should be no more than this value:
ESR = U_drop / I = 0.4V / 25.8mA ≈ 15.5 Ω
On the other hand, the online power profiler states that a single BLE advertisement event charge is 38.22 µC at 1.8V and 25.53 µC at 3.6V which roughly equals to max energy consumed:
E = q * V
E_3.6 = 25.53µC * 3.6V = 81.11 µJ
E_1.8 = 38.22µC * 1.8V = 68.8 µJAnd, for the worst case, assuming the energy as derived above and 0.4V as acceptable voltage drop, the minimum required capacity must be:
E = 1/2 * C * (Vh^2 - Vl^2)
C = 2 * E / (Vh^2 - Vl^2)
C = 2 * 81.11µJ / (2.2V^2 - 1.8V^2) = 102 µFOf course, it's required that the solar cell must be able to charge the supercapacitor between BLE events.
Also, I've noticed that in buck-boost mode the SPV1050 tends to charge the store and hence the battery to higher voltages. Such, the Harvester board has limited the U_eoc to 3.2V, but on the sun I can often observe it up to 3.5V. For this reason I'd recommend to slightly lower the U_eoc and ensure that the connected battery or the supercap can handle the voltage.
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@NeverDie said in 💬 The Harvester: ultimate power supply for the Raybeacon DK:
... and yet, isn't that a small battery I see on it? Maybe it's rechargeable, and cypress opted for that so as to save space as compared to a supercap? I haven't looked into it, but that's my guess.
I think I may have found the part: https://www.digikey.com/product-detail/en/elna-america/DCK-3R3E224U-E/604-1007-ND/970168
The picture seems to match. So, not a battery after all, but rather a supercap (one with rather high ESR). Likely 220mF, or thereabouts.@NeverDie Yeah, you're very close. Cypress has mentioned it in the datasheet. The PV panel is AM-1606C and the supercap is DCK-3R3E204T614-E.
It's also interesting to see that they have installed a second pool of ceramic capacitors to workaround high ESR of the supercap.
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I'm looking now at the ADP5091 boost chip by Analog Devices. It doesn't have a buck mode, but its boost mode is maybe just a tad more compelling than the spv1050's. It cold boots at 0.38v with 16ua of current, and after cold boot completes it can run on as little as 80mv. The pin pitch on its chip is 0.5mm as compared to 0.4mm for the SPV1050. Comparing it to the SPV1050 is perhaps splitting knits, but comparing it to every other chip on the market it does seem to require the least amount of power of any chip that I'm aware of.
https://www.analog.com/media/en/technical-documentation/data-sheets/ADP5091-5092.pdf
Analog Devices claims that its efficiency is 80%, so if running in buck mode is an option, I'm guessing that a buck converter would beat it. On the other hand, if there's enough light to provide the voltages for a buck converter to run on, then I'd wadge there's plenty of energy to be had regardless. At least, that's how I'm starting to look at it. I think the justification for a boost architecture is that it's preparation for the worst-case scenario, in the event that it ever occurs. I haven't yet decided whether it's like preparing for a once in 10,000 years flood or not. Perhaps it's just not practical. It's probably not a bad idea to have at least one to experiment with though.
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@NeverDie Cutting panels should just work. I'm unsure how do you attach wires to it though. I'll be grateful if you will share your findings.
This Cypress BLE sensor looks very sexy. It's definitely not so flexible as the Raybeacon, but it no doubt sets the tone and is ahead in both design and technology. I'm now thinking should I switch my nRF52 board from simple two-layers to high density interconnect and WLCSP - the aQFN-73 still not too easy to solder anyway, but it imposes serious space constraints.
I like the size and shape (still considering rounded square though) - it's about what I expect from a battery operated embedded development board. Also, I found the board area is enough to build a custom DIY module using 0603 components. But routing and component placement on the main board is somewhat tight. Maybe issue a "pro" version - with all features of a development board, but integration level of a BLE module? At least it will allow place the buttons symmetrically :)
@Mishka said in 💬 The Harvester: ultimate power supply for the Raybeacon DK:
@NeverDie Cutting panels should just work. I'm unsure how do you attach wires to it though. I'll be grateful if you will share your findings.
Closing the loop on your question, it looks as though they can be cut:
https://www.ebay.com/itm/0-5W-0-5V-High-Efficiency-Back-Contact-DIY-1-6-Cut-Sunpower-Solar-Cell-36pcs-lot/291858971298?hash=item43f4267aa2:g:hsAAAOSwxp9W5tui
I've read that cutting them with a laser is the recommended method. I only just came across this, and I haven't yet found a vendor selling just one solarpower solar cell lasercut into six pieces like that yet, although the above ebay auction demonstrates that you can buy them in bulk that way. -
Powerfilm makes a thin film solar cell which they say is good for energy harvesting at 200 lux and less. According to their flyer, at 200 lux it says the expected power is 220uW for the panel included in their Nordic nRF52832 solar development kit. However, at 100 lux the expected power is not 110uW (which would have been my guess), but instead only "1,430uW"! (Even though it's a USA based company, I'm assuming they're using the European convention of a comma instead of a period for decimal notation)
https://www.powerfilmsolar.com/media/cms/Indoor_Solar_Development_Kit_with_N_A90DF4062ABC1.pdf
Since they're "official" datapoints, I thought it worth reporting, not for the absolute magnitudes (which presumably should be a function of panel size) but for the relative magnitudes. I'd be curious if other types of solar cells also degrade as quickly when going from 200 lux down to 100 lux or whether some manage to do a lot better in terms of energy made available for harvesting. If not, then without resorting to larger panels it sounds as though somewhere around 100 lux or higher is the practical limit for small footprint sensors.
@NeverDie said in 💬 The Harvester: ultimate power supply for the Raybeacon DK:
somewhere around 100 lux or higher is the practical limit for small footprint sensors.
I'm realizing now that this is hogwash because today after getting my lux meter out of mothballs I'm noticing that my solar calculator works just fine down to around 15 lux, which is when its LCD starts to fade out. It suggests that powerfilm probably just isn't one of the better performing solar cells out there.
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@NeverDie said in 💬 The Harvester: ultimate power supply for the Raybeacon DK:
somewhere around 100 lux or higher is the practical limit for small footprint sensors.
I'm realizing now that this is hogwash because today after getting my lux meter out of mothballs I'm noticing that my solar calculator works just fine down to around 15 lux, which is when its LCD starts to fade out. It suggests that powerfilm probably just isn't one of the better performing solar cells out there.
@NeverDie Wow! Are you sure the lux meter is working properly? 15 lux is about as low as 25 cm from a candle fire which is awfully low.
So, since the ADP5091 is also on the list now, I think it becomes necessary to put all the mentioned power harvesters side by side so we can compare at least basic parameters. Please take a look to the Google Spreadsheet listing some of the tiny harvesters. Please note, The Analog Devices has about ten harvesters which may be described as "tiny", but so far the sheet is covering only ADP509x series. I'm going to add the LTC series later.
From brief analysis, it looks like the Startup Input Voltage and the Startup Input Power are placing the major constraint on PV panel. Of course, the panel should be also able to supply voltage required to cold-boot the harvester. Such, under the low-light conditions (50 lx to 100 lx in a dim room) power capabilities of both of my panels are simply not sufficient to bootstrap the SPV1050: the IXYS is too weak and works starting from 150 lx, and the SCNE is good for boost, but still require 150 lx to reach 2.6V at STORE (the data is for the charts I've posted earlier):
Therefore any panel which can reach required voltage and provide enough power should make the harvesting IC work. Please also note, that after cold-boot almost any harvester can work on a lower power (usually 1.5 - 3 times lower than it was required to start).
Also, in the table there is a class of super-tiny harvesters, namely the Cypress S6AE102(3)A and Ricoh R1800K. They can charge a store by harvesting source with less than 1µW capability. At the same time, the EM8500 looks like the most sophisticated embedded solution with lots of features. The rest of harvesters are quite nice ICs for a modular system.
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@NeverDie Wow! Are you sure the lux meter is working properly? 15 lux is about as low as 25 cm from a candle fire which is awfully low.
So, since the ADP5091 is also on the list now, I think it becomes necessary to put all the mentioned power harvesters side by side so we can compare at least basic parameters. Please take a look to the Google Spreadsheet listing some of the tiny harvesters. Please note, The Analog Devices has about ten harvesters which may be described as "tiny", but so far the sheet is covering only ADP509x series. I'm going to add the LTC series later.
From brief analysis, it looks like the Startup Input Voltage and the Startup Input Power are placing the major constraint on PV panel. Of course, the panel should be also able to supply voltage required to cold-boot the harvester. Such, under the low-light conditions (50 lx to 100 lx in a dim room) power capabilities of both of my panels are simply not sufficient to bootstrap the SPV1050: the IXYS is too weak and works starting from 150 lx, and the SCNE is good for boost, but still require 150 lx to reach 2.6V at STORE (the data is for the charts I've posted earlier):
Therefore any panel which can reach required voltage and provide enough power should make the harvesting IC work. Please also note, that after cold-boot almost any harvester can work on a lower power (usually 1.5 - 3 times lower than it was required to start).
Also, in the table there is a class of super-tiny harvesters, namely the Cypress S6AE102(3)A and Ricoh R1800K. They can charge a store by harvesting source with less than 1µW capability. At the same time, the EM8500 looks like the most sophisticated embedded solution with lots of features. The rest of harvesters are quite nice ICs for a modular system.
@Mishka said in 💬 The Harvester: ultimate power supply for the Raybeacon DK:
Wow! Are you sure the lux meter is working properly? 15 lux is about as low as 25 cm from a candle fire which is awfully low.
I used a cheap consumer grade lux meter to take the measurement, but it's consistent with what Dave Jones reported for the same solar calculator. He did a youtube video on it, and he showed it worked at around 20lux at a coarse level and probably a bit less.
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@NeverDie Wow! Are you sure the lux meter is working properly? 15 lux is about as low as 25 cm from a candle fire which is awfully low.
So, since the ADP5091 is also on the list now, I think it becomes necessary to put all the mentioned power harvesters side by side so we can compare at least basic parameters. Please take a look to the Google Spreadsheet listing some of the tiny harvesters. Please note, The Analog Devices has about ten harvesters which may be described as "tiny", but so far the sheet is covering only ADP509x series. I'm going to add the LTC series later.
From brief analysis, it looks like the Startup Input Voltage and the Startup Input Power are placing the major constraint on PV panel. Of course, the panel should be also able to supply voltage required to cold-boot the harvester. Such, under the low-light conditions (50 lx to 100 lx in a dim room) power capabilities of both of my panels are simply not sufficient to bootstrap the SPV1050: the IXYS is too weak and works starting from 150 lx, and the SCNE is good for boost, but still require 150 lx to reach 2.6V at STORE (the data is for the charts I've posted earlier):
Therefore any panel which can reach required voltage and provide enough power should make the harvesting IC work. Please also note, that after cold-boot almost any harvester can work on a lower power (usually 1.5 - 3 times lower than it was required to start).
Also, in the table there is a class of super-tiny harvesters, namely the Cypress S6AE102(3)A and Ricoh R1800K. They can charge a store by harvesting source with less than 1µW capability. At the same time, the EM8500 looks like the most sophisticated embedded solution with lots of features. The rest of harvesters are quite nice ICs for a modular system.
@Mishka This is probably worth adding to the list: https://e-peas.com/products/energy-harvesting/photovoltaic/aem10941/
If we add that, I think we have a pretty complete list for a first pass. The e-peas is pretty expensive though, so we could drop it for that reason.
Since covering the worst case seems to be a relevant concern, I think it's important to identify which one can start-up and begin harvesting at the lowest lux level.
15 lux doesn't seem all that dim to the eye. Setting aside the explanation that our eyes have great dynamic range, I still think we should be able to harvest from less than that. I mean, people are able to harvest from fairly weak radio waves, which have far less power.
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@Mishka This is probably worth adding to the list: https://e-peas.com/products/energy-harvesting/photovoltaic/aem10941/
If we add that, I think we have a pretty complete list for a first pass. The e-peas is pretty expensive though, so we could drop it for that reason.
Since covering the worst case seems to be a relevant concern, I think it's important to identify which one can start-up and begin harvesting at the lowest lux level.
15 lux doesn't seem all that dim to the eye. Setting aside the explanation that our eyes have great dynamic range, I still think we should be able to harvest from less than that. I mean, people are able to harvest from fairly weak radio waves, which have far less power.
@NeverDie Added, thanks! Quite interesting the IC implements some kind of Cuk converter. On the bad side it seems stocked nowhere, but the e-peas only.
Looking for reasons why the Cypress BLE sensor has chosen a Panasonic cell I found the catalogue which also contains number of interesting charts. Such, the chart on page 3 explains why a calculator cell is more efficient in artificial light than the IXYS thing (BTW the IXYS datasheet has it pretty flat on the range from 400 nm to 1100nm).
This all makes me think that there are basically two combos to choose from:
- an amorphous cell and 3µW harvester
- a monocrystalline cell and 15µW harvester with voltage adjusted to panel assembly
But to be honest I'm quite surprised how well performs the SCNE cell I have extracted from the noname calculator.
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@NeverDie Added, thanks! Quite interesting the IC implements some kind of Cuk converter. On the bad side it seems stocked nowhere, but the e-peas only.
Looking for reasons why the Cypress BLE sensor has chosen a Panasonic cell I found the catalogue which also contains number of interesting charts. Such, the chart on page 3 explains why a calculator cell is more efficient in artificial light than the IXYS thing (BTW the IXYS datasheet has it pretty flat on the range from 400 nm to 1100nm).
This all makes me think that there are basically two combos to choose from:
- an amorphous cell and 3µW harvester
- a monocrystalline cell and 15µW harvester with voltage adjusted to panel assembly
But to be honest I'm quite surprised how well performs the SCNE cell I have extracted from the noname calculator.
@Mishka said in 💬 The Harvester: ultimate power supply for the Raybeacon DK:
This all makes me think that there are basically two combos to choose from:
Not quite. After closer look I've found the AM-5610 outdoor panel of suitable size - only 25x20mm. The panel is capable to produce up to 18mW.
Other interesting panels are: AM-1606 as used on the Cypress BLE, 15x15mm, AM-1456 which is close to SolarBit by size, 25x10mm, and AM-1312 which is exactly of the same size the SCNE I have.
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@Mishka said in 💬 The Harvester: ultimate power supply for the Raybeacon DK:
This all makes me think that there are basically two combos to choose from:
Not quite. After closer look I've found the AM-5610 outdoor panel of suitable size - only 25x20mm. The panel is capable to produce up to 18mW.
Other interesting panels are: AM-1606 as used on the Cypress BLE, 15x15mm, AM-1456 which is close to SolarBit by size, 25x10mm, and AM-1312 which is exactly of the same size the SCNE I have.
@Mishka I suppose the SC-3722-9 may be too big for your project, but it's worth mentioning because it performs pretty decently under indoor lighting, and you can extract them for cheap from $1 solar keychains, which are widely available. That's all subjective though. I'm not sure how they compare by the numbers.
