Node running on supercaps and a solar panel.
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@neverdie I think you are right. I have tinkered with your other boost converter - https://www.openhardware.io/view/279/Adjustable-Boost-Converter-with-Pass-Through
MCP1640's quiescent current is much higher 19uA.
Now, I'll try to run it from the supercapacitor directly. Pity that anything below 1.9V is going to be wasted (nrf24l01+ is unstable around 1.9V)
@alexsh1 said in Node running on supercaps and a solar panel.:
MCP1640's quiescent current is much higher 19uA.
Or, better yet, just turn it on prior to your sensor readings, and then turn it off.
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@alexsh1 said in Node running on supercaps and a solar panel.:
MCP1640's quiescent current is much higher 19uA.
Or, better yet, just turn it on prior to your sensor readings, and then turn it off.
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@alexsh1 said in Node running on supercaps and a solar panel.:
I managed to find a very small, but efficient solar cell smaller than in the photo.
Please do tell: what did you find? And where?
@neverdie sure - this is the one i am very much happy with. Previous one was not supplying enough juice to charge fully supercaps.
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@neverdie you mean like using a mosfet or something?
It is used to supply 3.3v to atmega328p, I do not think I can just turn it off.@alexsh1 said in Node running on supercaps and a solar panel.:
@neverdie you mean like using a mosfet or something?
It is used to supply 3.3v to atmega328p, I do not think I can just turn it off.Sorry, I meant switch to "pass through".
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@alexsh1 said in Node running on supercaps and a solar panel.:
@neverdie you mean like using a mosfet or something?
It is used to supply 3.3v to atmega328p, I do not think I can just turn it off.Sorry, I meant switch to "pass through".
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That is something you can do by leaving the supercap on a desk for 24 hours and a multimeter 😁
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Did anyone try using 3V solar cell for 2.7V caps?
Seems a perfect fit - no need to use two supercaps in series -
@alexsh1 said in Node running on supercaps and a solar panel.:
@neverdie you mean like using a mosfet or something?
It is used to supply 3.3v to atmega328p, I do not think I can just turn it off.Sorry, I meant switch to "pass through".
@neverdie Did you make any estimates running your mote on supercap? I cannot understand how come on RFM69HW (lowpowerlab), this guy managed to extract 14,111 packets transmitted https://lowpowerlab.com/forum/projects/a-solar-supercap-powered-moteino/
This is on 15F supercap.
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@neverdie Did you make any estimates running your mote on supercap? I cannot understand how come on RFM69HW (lowpowerlab), this guy managed to extract 14,111 packets transmitted https://lowpowerlab.com/forum/projects/a-solar-supercap-powered-moteino/
This is on 15F supercap.
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@neverdie I am not questioning his numbers. I am trying to understand why with a normal transceiver (non-H) I am getting so much less. I must admit also that with BQ25570, I have 2x10F in series, which makes it 5F in total only vs 15F.
I should wait until my 30F cap runs out of juice and see how many packets I extracted
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If you are happy with your setup to power the node, why are you bothering that much to send that many more packets if you actually don't need them anyway?
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If you are happy with your setup to power the node, why are you bothering that much to send that many more packets if you actually don't need them anyway?
@gohan However, in the nutshell you are right. With a small solar battery (53mm x 30mm, 5V 0.15W), this is what I get:
and today is an extremely cloudy day (no sun at all). Harvesting works really well.
I implemented a voltage divider yesterday with 1.8M / 470k resistors. Now I can monitor voltage in Domoticz:
voltage at 22:00 yesterday - 4.797V
voltage at 12:00 today - 4.887V -
Try running with your fuses set to xFF xDA xC2, That way your BOD will be turned off, you'll be running from the internal 8mhz resonator, and you'll be waking from sleep in <4uSec.
@neverdie I have already all that. I am using this node https://www.openhardware.io/view/76/Stamp-size-MySensor-node
Let's see when I have final results. I have this supercap AVX 30F with ESR = 0.02ohm (vs Vishay 15F ESR=1.8Ohm used with Moteino and BQ25570 at lowpowerlab)
EDIT: Another point is signing/encryption. This would affect supercap charge as the node would be transmitting more data to GW.
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@gohan However, in the nutshell you are right. With a small solar battery (53mm x 30mm, 5V 0.15W), this is what I get:
and today is an extremely cloudy day (no sun at all). Harvesting works really well.
I implemented a voltage divider yesterday with 1.8M / 470k resistors. Now I can monitor voltage in Domoticz:
voltage at 22:00 yesterday - 4.797V
voltage at 12:00 today - 4.887V@alexsh1 I use a total of 20F 5.5V supercaps and they discharge much more during night most likely because the buck/boost converter is not very low power and supercaps are chinese quality, but as far as I can get 36/48h of runtime without solar charge I should be fine
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@alexsh1 I use a total of 20F 5.5V supercaps and they discharge much more during night most likely because the buck/boost converter is not very low power and supercaps are chinese quality, but as far as I can get 36/48h of runtime without solar charge I should be fine
@gohan As you may see from the graph above my self discharge + sleep/tx consumption during the night dropped voltage from 4.851V at 21:00 (I charged supercaps initially) to 4.549V at 08:00. This is the rate of about 0.3V per 12 hours, I estimate that I have around 10 days without any charging before I run out of energy.
It took 4h 25mins on a cloudy day (see another graph) to get 2x10F in series supercaps fully charged to 5.047V
