Node running on supercaps and a solar panel.
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I have got my hands on 30F 2.7V supercapacitor.
With it was charged for the first time, it only lasted sending 2583 times (1 time a minute voltage and an 20ms LED pulse and then sleeping; sleeping consumption is 4-5uA). The number is a bit disappointing. It is however connected via boost MCP1640 to provide the node with a stable 3.3V. I may try to get the supercapacitor connected directly to the node to see if I can extract more packets.
@alexsh1 said in Node running on supercaps and a solar panel.:
I may try to get the supercapacitor connected directly to the node to see if I can extract more packets.
That's your best choice, unless you're also running a PIR or something that requires a higher minimum voltage. In that case, you could switch to this boost converter, which has only 7ua quiescent current:
https://www.openhardware.io/view/285/33v-Boost-Converter-with-Pass-Through -
@alexsh1 said in Node running on supercaps and a solar panel.:
I may try to get the supercapacitor connected directly to the node to see if I can extract more packets.
That's your best choice, unless you're also running a PIR or something that requires a higher minimum voltage. In that case, you could switch to this boost converter, which has only 7ua quiescent current:
https://www.openhardware.io/view/285/33v-Boost-Converter-with-Pass-Through@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)
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I bet you will see a proportional drop according to the number of values you want to report. I am still stressing it a bit, so I think there may be margin to save some power by sending less important values with a lower frequency
@gohan Just to let you know. I have been running this node with Si1132 + Si7021 + another sensor (reporting more than 6 values every 5-10 mins) for weeks now. I have just measured the caps = 4.8V (peak is around 5.2V) - it is late at night. In the morning the voltage will go up. I managed to find a very small, but efficient solar cell smaller than in the photo.
The key is to have a low sleeping consumption, i.e. all sensors must sleep properly. In this case you get 4-8uA sleeping current and can live on supercaps for days without recharge.
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@gohan Just to let you know. I have been running this node with Si1132 + Si7021 + another sensor (reporting more than 6 values every 5-10 mins) for weeks now. I have just measured the caps = 4.8V (peak is around 5.2V) - it is late at night. In the morning the voltage will go up. I managed to find a very small, but efficient solar cell smaller than in the photo.
The key is to have a low sleeping consumption, i.e. all sensors must sleep properly. In this case you get 4-8uA sleeping current and can live on supercaps for days without recharge.
@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?
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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
