Supercap Solar Powered Mysensors nodes as cheap as possible
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Now voltage stays between 2 and 2.4V (it should be 2.62V but I need to adjust the buck converter and add 0.2V as they are lost though the diode now). I don't understand why the voltage is so unstable now during discharge hours -
@xydix In what sense do you mean optimal? I think what separates our approaches is that gohan wants to buy readymade parts off aliexpress and, if possible, connect them with dupont wires. So, if that rings true for you, then you will probably find his approach more optimal.
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@xydix In what sense do you mean optimal? I think what separates our approaches is that gohan wants to buy readymade parts off aliexpress and, if possible, connect them with dupont wires. So, if that rings true for you, then you will probably find his approach more optimal.
@NeverDie Doesn't matter for me. I have seen your boards on openhardware for solar panels. Interesting.
In many cases an custom PCB get pretty expensive if you just want 1 or 2 board because buy all components required, these are often is selled in 10 pcs or more.
In my case, I want something that works, then if i can get away with just an LDO on an protoboard im fine with that.
I try to build as cheap nodes as possible.
Then if i can find cheap stuff in aliexpress that is doing the job, thats fine.
Have you had any good results useing solar panel indoors? -
@NeverDie Doesn't matter for me. I have seen your boards on openhardware for solar panels. Interesting.
In many cases an custom PCB get pretty expensive if you just want 1 or 2 board because buy all components required, these are often is selled in 10 pcs or more.
In my case, I want something that works, then if i can get away with just an LDO on an protoboard im fine with that.
I try to build as cheap nodes as possible.
Then if i can find cheap stuff in aliexpress that is doing the job, thats fine.
Have you had any good results useing solar panel indoors?@xydix said in Supercap Solar Powered Mysensors nodes as cheap as possible:
Have you had any good results useing solar panel indoors?
Definitely yes. A typical $1 6v solar panel together with an LDO and diode works fine. At least for me. Gohan is exploring something altogether different, and I'd rather not derail his thread. So, if you want more detail, just read the thread I wrote previously.
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I'll let go until Saturday, then I'll do the voltage adjustment and try to discharge the supercap and see if is is able to recover from that condition. If it doesn't I'll need to find a piece of hardware that will have to hold the booster from switching on until a minimum voltage is reached and also add some dynamic sleep time that increases as the voltage decreases below certain levels
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@NeverDie Doesn't matter for me. I have seen your boards on openhardware for solar panels. Interesting.
In many cases an custom PCB get pretty expensive if you just want 1 or 2 board because buy all components required, these are often is selled in 10 pcs or more.
In my case, I want something that works, then if i can get away with just an LDO on an protoboard im fine with that.
I try to build as cheap nodes as possible.
Then if i can find cheap stuff in aliexpress that is doing the job, thats fine.
Have you had any good results useing solar panel indoors?@xydix said in Supercap Solar Powered Mysensors nodes as cheap as possible:
@NeverDie Doesn't matter for me. I have seen your boards on openhardware for solar panels. Interesting.
In many cases an custom PCB get pretty expensive if you just want 1 or 2 board because buy all components required, these are often is selled in 10 pcs or more.
In my case, I want something that works, then if i can get away with just an LDO on an protoboard im fine with that.
I try to build as cheap nodes as possible.
Then if i can find cheap stuff in aliexpress that is doing the job, thats fine.If you want the barest minimum of parts, I've also done it with just a solar panel, a diode, a supercap, and mcu+radio. That's it. Then the trick is to have your mcu monitor the voltage on the supercap. As the voltage approaches the limit, the MCU turns on the radio receiver to burn off extra current, so that the voltage never exceeds the supercap's limit (usually 2.7v). It works.
Having said all that, though, I'm interested in what Gohan will come up with. I'm sure his approach will work too. :)
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I'm kind of stuck in finding any ready made product for balancing, so I'm looking at the ALD810026 sab mosfet chip and mount it on a 8soic to dip adapter. It's the closest I could get without the need to print out a pcb. What do you think?
@gohan said in Supercap Solar Powered Mysensors nodes as cheap as possible:
ALD810026
I haven't tried to do balancing, so you're guess is probably better than mine. The guy with the swiss accent had a circuit for it. Your solution sounds better than his though because his only worked while charging to maximum charge whereas yours maybe balances after-the-fact and/or to less charges as well?
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Yes, he used those pcbs from aliexpress that do overvoltage protection, but those are sized for much bigger caps and wouldn't fit much into small boxes. For what I could understand the sab mosfets work while the supercap discharges to keep voltage even across them, so you have to be careful not to apply a higher voltage than the maximum combined of the caps in series. If I could find a way to make a overvoltage protection with some simple components I'd be fine with it.
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Not long ago someone (was it you?) posted a link to a youtube video where some guy had a charge balancing circuit that wasted very little power, IIRC. He's probably selling it now. Maybe you could just buy one of those?
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I maybe up to something: I used a MCP1700 ldo and on Vout a diode + a schottky in series to drop the voltage ( could have used just the diode, but the Vout was 2.7x volts so for supercap longevity I added the schottky to have a safe margin) and it is charging even with panel pointed away from the sun. I'll see how it goes tomorrow, but I am pretty happy with the results so far. If it works I think i can't go cheaper then a LDO + 2 diodes :v:
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What is the cost? Also, it's not clear to me how much usable charge you're getting.
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1.5€ for solar panel, 1.7€ for 100F supercap, 1€ for booster and some cents for MCP1700, diodes and a small PCB. A fully charged supercap gives 3 days of working time, with send every 10 minutes of temp. hum, TX rssi, RX RSSI, battery voltage and battery percentage
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Sounds sorta roughly like the kind of circuit used in solar garden lamps, except you've replaced the typical rechargeable battery with a supercap and are boosting to a higher voltage than they typically do. I wonder whether any of them do boost to the same voltage that you're targeting? Perhaps the brighter ones, for example? Those solar garden lights typically have a single, inexpensive integrated circuit that does it all.
