Author Topic: Weathershield + solar panel + supercap  (Read 640 times)

Kilo95

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Weathershield + solar panel + supercap
« on: June 17, 2019, 10:06:55 AM »
I've been running a WS +solar panel+ supercap for a year and a half without any issues. my solder joint on the solar panel gave way over the weekend and the supercap discharged completely. I resoldered the joint and placed it back in the sun and it showed 5v after a while per my DMM. I cant seem to get it to stay connected to the gateway anymore though.

1. My WS is ~150ft from the gateway. Usually runs RSSI mid to upper 90s.
2. Tried unplugging power, plugging back in near the house and moving it out to the usual location incrementally over 15 min. still drops out.
3. I'm using one of the ChemE PCB dipoles.
4. If I d/c power and reconnect to reset out at the spot I usually have it installed, it shows up in the gateway once or twice and then drops out.

any thoughts?

ssmall

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Re: Weathershield + solar panel + supercap
« Reply #1 on: June 17, 2019, 10:58:11 AM »
Are you using ATC?  Sometimes when I work on a node I do that in the house and the communication is fine.  When I move the node to it's final spot out in the yard somewhere, the node stops communicating for a while till it dials up the transmission power enough for the gateway to receive the transmission  then it works just fine.

Kilo95

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Re: Weathershield + solar panel + supercap
« Reply #2 on: June 17, 2019, 11:10:14 AM »
It's been a year and a half since I programmed it.  I'm 99% sure the answer is yes. That's why I was trying to move it out incrementally so it would never completely drop out. It's been 13 hrs since it last reported in to the gateway.

ssmall

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Re: Weathershield + solar panel + supercap
« Reply #3 on: June 17, 2019, 12:17:34 PM »
It doesn't take that long for mine to come back.

HeneryH

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Re: Weathershield + solar panel + supercap
« Reply #4 on: June 17, 2019, 02:35:30 PM »
Slightly off topic...  what are you folks doing, if anything, to have a clean power cutoff and activation when the cap is going above or below the acceptable power level.

Right now I have no extra logic so my cap will gradually discharge until the Mote goes unstable in some way and eventually shuts off.  On charge, the cap gradually charges and at some point the Mote has enough power but has gone sufficiently berzerk that it doesn't properly run.

I need to turn the power switch off on the power shield until I can measure enough charge on the cap then throw the switch on to get it to boot.

It would be nice to have some logic that cleanly cuts or applies power at the threshold.

ssmall

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Re: Weathershield + solar panel + supercap
« Reply #5 on: June 17, 2019, 02:50:21 PM »
I have gone a different route.  I took a regular Moteino and removed the regulator and bridged the gap Vin and Vout on the regulator with solder.  I then changed the fuses so that the Moteino runs at 8Mhz.  I use 2 AA batteries with a Moteino and WeatherShield and it lasts at least a year without any issues.  The temp got to -30 Fahrenheit this winter where I live, no problems.

The conversion process I have gone though is no longer necessary now that Felix sells them in his store.

HeneryH

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Re: Weathershield + solar panel + supercap
« Reply #6 on: June 17, 2019, 03:06:37 PM »
I see a similar question at https://lowpowerlab.com/forum/moteino/what-happens-when-the-power-goes-out/
Slightly off topic...  what are you folks doing, if anything, to have a clean power cutoff and activation when the cap is going above or below the acceptable power level.

Right now I have no extra logic so my cap will gradually discharge until the Mote goes unstable in some way and eventually shuts off.  On charge, the cap gradually charges and at some point the Mote has enough power but has gone sufficiently berzerk that it doesn't properly run.

I need to turn the power switch off on the power shield until I can measure enough charge on the cap then throw the switch on to get it to boot.

It would be nice to have some logic that cleanly cuts or applies power at the threshold.

Felix

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Re: Weathershield + solar panel + supercap
« Reply #7 on: June 18, 2019, 09:21:13 AM »
When you have the LDO, and also the radio/flash, you have to account for those components.
They have VCC limits and a dropout for the LDO.

Also, the supercaps take a "long" time to charge from a solar cell when depleted. So having the Moteino/load attached during charging from depletion will not work well.
Either you charge the supercap from a PSU, then connect it to the solar cell and Moteino so the cell can sustain it, or charge it fully from the cell and then attach the Moteino.

HeneryH

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Re: Weathershield + solar panel + supercap
« Reply #8 on: June 18, 2019, 09:58:53 AM »
When you have the LDO, and also the radio/flash, you have to account for those components.
They have VCC limits and a dropout for the LDO.

Also, the supercaps take a "long" time to charge from a solar cell when depleted. So having the Moteino/load attached during charging from depletion will not work well.
Either you charge the supercap from a PSU, then connect it to the solar cell and Moteino so the cell can sustain it, or charge it fully from the cell and then attach the Moteino.
Both of which are fundamentally incompatible with unattended operations. Unless there are external circuity added to make it behave this way.

Felix

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Re: Weathershield + solar panel + supercap
« Reply #9 on: June 18, 2019, 10:03:06 AM »
Both of which are fundamentally incompatible with unattended operations. Unless there are external circuity added to make it behave this way.

Yes and no.
You already have to go out there and physically install the mote, correct?
So I meant ... you have to do that charging of the scap once. Before you deploy the mote/supercap/solar cell. That's because we assume you have a fairly small solar cell, otherwise this pre-charge would not be required, a huge solar panel would quickly charge your scap regardless if the Moteino in BOD draws a few mA.

So the idea is you have to start from a charged state. Or else if the solar cell is too small it might not be able to charge the scap while the Moteino is in BOD.
« Last Edit: June 18, 2019, 05:23:58 PM by Felix »

HeneryH

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Re: Weathershield + solar panel + supercap
« Reply #10 on: June 18, 2019, 02:02:09 PM »
I suppose you are right that in practice, if you pre-charge your cap, then under normal operations the solar panel should keep the levels safe.  Normally, the levels should not drop below safe levels so not much of a worry.

Kilo95

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Re: Weathershield + solar panel + supercap
« Reply #11 on: June 19, 2019, 09:31:51 AM »
Thanks for all the advice.

I do agree that it is a supercap power issue. I left it up near my house outside and it stays connected until the SC is depleted (3.35v). I have a very high degree of suspicion that the solar panel is getting weak or going bad. I replaced it with another small one I had (I've ordered some more and will make a 2-3 panel array when they arrive). Right now I'm just using a single 6v (not sure of the amperage) panel. I'm pretty sure that's my issue. We haven't had much sun lately. It's been very cloudy here. I'll check back in once I can confirm this. Thanks again

Felix

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Re: Weathershield + solar panel + supercap
« Reply #12 on: June 19, 2019, 10:40:19 AM »
If you use my Gateway software, which can log the voltage, or anything else that can graph your scap voltage, you can watch as it charges/discharges every day (when solar cell gets enough sunlight).

Kilo95

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Re: Weathershield + solar panel + supercap
« Reply #13 on: June 20, 2019, 08:50:50 AM »
I do use your gateway software. It d/c to around 3.7v last night after being in the sunlight and not turned on yesterday all day. Never dropped out this time. I believe the issue was the scap wasn't completely charged and with the single solar panel and completely cloudy days, the scap wasn't getting charged all the way. I believe we're good now. Thanks!

Felix

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Re: Weathershield + solar panel + supercap
« Reply #14 on: June 20, 2019, 09:02:33 AM »
In which case it's a combination of a few factors:

- keeping the Moteino in low enough sleep power
- large enough scap
- large enough solar cell to harvest energy on sunny days, that can keep the mote going with 1-2 days of overcast