Node running on supercaps and a solar panel.

[alexsh1]

@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

[NeverDie]

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.

[alexsh1]

@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.

[gohan]

@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

[alexsh1]

@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

[gohan]

You are using a very efficient circuit and good quality supercaps, I loose about 1V in 12 hours

[alexsh1]

@gohan Did you try to measure your sleeping current?

[NeverDie]

@alexsh1 said in Node running on supercaps and a solar panel.:

I am using this node https://www.openhardware.io/view/76/Stamp-size-MySensor-node

If anything, you should have an advantage, since the nRF24L01 transmits at a faster bitrate, and using significantly less Tx power also.

[NeverDie]

Are you using the passive mode option for mysensors? If not, that could be part of what's draining you.

[alexsh1]

@neverdie said in Node running on supercaps and a solar panel.:

passive mode option for mysensors

I did notice there is an option:

#define MY_PASSIVE_NODE

What is the passive node option please?
I am not using it and yet I do not have any problems with draining

EDIT: I see now

    All transport-related checks and safety-mechanisms are disabled. 
    Requires that MY_NODE_ID is set, MY_PARENT_NODE_ID and MY_PARENT_NODE_IS_STATIC are optional. 
    Singing, registration, and OTA FW update are disabled. 

[alexsh1]

In my view disabling transport related checks is not an option.
Singing, registration, and OTA FW do take a lot of power. Especially OTA. It is slow and takes a lot of up time.

[NeverDie]

It sounds like you're happy already. Good luck!

[gohan]

If I remeber well, passive node is used when you have a very tiny node, with low memory that only send data one way, like RF433

[alexsh1]

@gohan OK, but I think the key here is to get consumption down to something meaningful - 5uA or something. The only down side when not using a passive node is that if GW is disconnected, node would not go to sleep, but will be trying to connect to GW. define MY_TRANSPORT_UPLINK_CHECK_DISABLED would disable the node sending more than MY_TRANSPORT_STATE_RETRIES times message

[gohan]

even if it drains the battery when the GW is dead, it is no big deal as you just have to wait for some sunlight

[alexsh1]

@gohan True! I was more talking about super small nodes working on CR1632. I have a few of these.

[alexsh1]

Another interesting set of graphs (voltage scale is wrong - please ignore):

This is with signing:

This is without signing:

[gohan]

It looks a little irregular to me, doesn't it?

[alexsh1]

@gohan Well, the point is that signing does take more tx time. Therefore, voltage does drop upto 0.2-0.3V.

I am not sure about irregularities though

[gohan]

Maybe it has to do with the harvesting chip. My graph looks like a sawtooth from day to day.