There is a fair amount of discussion about solar powered nodes.
If there is enough interest I’m willing to do a ‘most for least’ budget build / walk through.
I’m thinking a solar flood light and LILYGO® TTGO ESP32-Paxcounter LoRa32 V2.1 1.6 as the starting point.
I like this board because it has the SD-Card option, and I hope well will be able to use that for message store and forward as well as possibilities that open up with a revised web interface.
This could easily evolve into a community information radiator.
There are few use cases requiring WiFi and solar on the same device, so for the overwhelming majority of solar uses cases NRF52 makes a lot more sense.
I may demo such a build, but first I think I want to collect some real world data on how much runtime an esp32 setup can have on very cheep solar setups. Half the cost is only one reason, the other is what kind of expanded uses with the wifi are possible.
I had this funny idea the other night. What if, when playing hide and seek with your buddies in an English home in the summer, you stepped through the back of your Uncles wardrobe into a snow covered forest. Whatever you stepped through is gone, you have no way back to shelter and the known. You check your phone, no cell service, and wifi isn’t connected. But there is a single wireless network. SSID is simply Connect2Me (Shout out to Allice in Wonder land fans). You connect to the wifi, your phone opens a web page and you think it is a logon page. But its not, its a Wanted Dead or Alive poster for a White Witch on a sleigh known for offering strangers candy. Next to the Poster was a link to another website: narnia.wiki
Going to need a pretty big panel and solar management system to run a ESP32 with WiFi running, without wifi and ESP32 I have found you need at least a 10 watt panel to get to 30 days, so you are going to need 2-3X that at least to run WiFi.
Very interested yes, thank you.
I already own a lot of ESP32 LoRa devices (Lora32) for various good reasons, including historical availability of the hardware, low price delivered in my area, historical support of Meshtastic, versatility of the ESP32 chip etc.
Hopefully, power consumption on this platform will get low enough that solar powered relays will be doable.
As far as I am concerned, I am looking for strict remote relay mode, therefore no need for display, bluetooth, wifi and so on. Only radio listening and repeating.
This solar setup ran ESP32 + wifi reliably with a 30w panel. It also worked in <0c conditions which is something to consider in much of the world. Freezing temps are a challenge for lithium chemistries.
Thank you for the link with the detailed setup.
However, a 30W panel is really a lot, this will take a lot of space, be very visible, may be stolen, may be exposed to high wind etc.
We should keep in mind that LoRa at its core is a low power radio technology. We are talking about something like 0.1W during Tx time.
ESP32 offers various sleeping modes and tweaks that can bring down the power draw down to about 10mA.
A remote relay node does not need much more than LoRa radio listening, and repeating.
Yes as I said this was for Wifi. You’ll also find that in practice you need more solar than the paper calculations suggest, dust covers panels, batteries take longer to charge, circuits are less efficient than the spec sheet etc etc.
For a Nrf52 and not using wifi you could of course go smaller. I’d still pay attention to how lithium charges in sub 0c temps if that is a consideration in your part of the world.
ESP32 sleep tweaks have proven very buggy in practice and I have never seen a node run at 10mA for very long unless the router is the only node on the mesh.
I have a growing collection of ideas for a series of related projects.
Along the lines of ‘most for least’ my first project in this series will not have 24/7 really cold or very hot operating conditions in mind.
First build will likely be day light hours only, with the idea for easy to connect a USB battery bank to expand operation time regardless of solar input. This can provide a lot of initial function for low cost, but in an emergency activating the node is just a USB connection away.
I’m thinking of this first project as a community node more than an individual user. Could be a singe home / family, or a remote village. The main goal is to make information available.
The final stage of the first phase would be two or more community nodes working together to cover wider, but still local area.
The second phase goal would be linking distant community nodes possibly using a ‘relay node’, but also mobile devices that travel between places that have Store and Forward plugin enabled. Think about that for a second, someone who needs to travel between two places not direct radio range could sneaker-net messages between villages. Not ideal, doesn’t meet 1st world connective standards, but in places and times where traditional systems are not available it could be as big or bigger than the Pony Express was back in its day.
Another use case that came to mind again is events like Burning Man.
I think a key part of the ideas forming as I think of this is no app downloads required. It really should be as easy as connecting to a Wi-Fi network with a phone that has a web browser. For events like Burning Man that could be a huge difference in how many people are able to interact with and via the projects.
This thread is turning in to a place for me to keep various ideas and see what others imagine.
Maybe some of the coders can help grow an idea I had. Would it take much code wise to enable / disable features, or trigger sleep timers when the esp32 reads specific voltage ranges? First thing I’d like to implement would be turn on/off wifi based on battery voltage. I envision when exposed to sun light even modest solar setups can manage the various power requirements, but as light fades maybe the device switches in to relay only mode, no wi-fi or Bluetooth. This preserves the communications aspect, and maybe a button press could allow someone to enable wifi for a set period of time.
Unfortunately, I have no experience in programming with ESP32 sleep states to give a hand now, sorry.
10mA is well within the theoretical specs of the MCU (which is a ESP32-PICO-D4 on my TTGO LORA32 boards). Actually, they are supposed to be able to go even lower, about 1mA in light sleep state, with ULP coprocessor and RTC active. Don’t they get that low in your experience ?
Maybe some settings for power-constrained nodes would help to keep them asleep as long as there is no message to repeat. For this type of nodes, in my opinion, led blinking or presence relaying could be disabled if users don’t need it, in order to same power and keep MCU asleep as long as possible.
What do you think about it ?
I actually beside the power consumption, hope the phone app could have capability to transfer very low resolution photos someday. I know this is not easy for Lora… But I still want to try to optimize the RF design to achieve lower time on air with acceptable coverage. Maybe I expected too much
I don’t think trying to do low power ESP32 is very productive as most solar or battery use cases will have WiFi off, and if you do want to do WiFI you are going to need a road sign sized panel. The NRF52 boards use 10x less power (vs a ESP32 with wifi off) and don’t sleep at all. ESP32 sleep code has been buggy and problematic from the start (both for meshtastic and other projects).
Honestly is_router as currently set up is pretty useless for any stationary mesh, it is only helpful if you have stationary nodes that are totally out of range of all other nodes and receive no packets for extended periods of time.
I am new here, but my thoughts are a 12v panel charging a 12v gel filled battery. Then car usb 12v plug charger to step down to 5 volts in usb cable. USB cable to back of tbeam. This setup is common for wildlife feeders that are self sustaining for over a year.
What is wattage needed for device?
Battery is 96 watt hours. (8ah x 12v) and $25.
12v panel is 10 watts for $35 or 20watts for $50
Battery probably shouldn’t be drained below 50% to facilitate maximum health. More could be hooked up in parallel if needed.
Also, I posted a question on relay nodes, because I am very new to Meshtastic. Can any mods unlock that post? Some bot has hidden it.
The feeders probably use a very predictable amount of power as I imagine the whole thing just runs on timers. Meshtastic is pretty random and depends on activity. A stationary ESP32 node in range of other nodes probably uses ~60mA if wifi is off ~200mA with wifi on. I just don’t see the point of forcing the square peg into a round hole when you can use a nrf that maxes out at about 15mA
I just mention wildlife feeder battery, because once setup they are very robust and last for years without maintenance. They are also extremely common in any rural hardware store.
.2 amps x 12v x 24 hours = 57.6 watt hours per day which is ball park territory for a 96 watt hour battery.
Also they use the same setup (although slightly larger) on automatic gate openers that aren’t connected to meter. They move a substantial load at many sporadic intervals.
Indeed NRF52 is certainly technically superior for low power use case.
However, I suspect ESP32 is the most widely owned platform for meshtastic users. Improving behavior on this target will improve experience for a lot of meshtastic users. I would be interested to have figures about it though.
