The Krahôs are a sovereign people that inhabit the savannas of Brazil. Most of their villages are isolated without electricity or any form of communication. During the pandemic communicating with each other has become crucial to saving lives.
Together with them we’re planning on creating the above mesh using Heltec Lora devices, connected to 10W panels and battery, as relay nodes placed on strategic hilltops. In the villages people will connect T-Beams to phones to send messages using the Android app.
These were chosen because of the availability in Brazil, without having to wait for stuff from China. Unforunately the moxon antenas aren’t available here, so would have to either find a place to 3D print them or wait…
I’ll also be ordering a pair of Rak4600 boards, pointed out by @sam_uk as super power efficient, but not counting on them and ready to wait as they’re coming from China.
Thanks for the support @geeksville! Getting any message over these 43Km, even if it takes a minute, is amazing for the price it’ll cost.
Direct messaging isn’t really required for now, every device will represent a village. But certainly would be great in the future. On that, I’d love to see this get integrated as a transport for distributed protocols, most specially Secure Scuttlebutt. I believe slowly syncing json files is realistic for this kind of protocol, and ideal for creating a bridge over the WWW using a GSM module, and connecting to great existing apps such as Manyverse and Ahau. Social networking over LoRa. Won’t be sending pics or videos, but still great for sharing stories. Building a SSB mqqt plugin would be the way I suspect.
Starting to explore the code-base in hopes of tweaking and collaborating. Going to sleep isn’t a bad idea, but I’d like to chage the range according to needs.
Waiting for a few more confirmations that this is a good plan before ordering the parts. Will be around $400 USD buying everything in Brazil but the moxons and rak4600, which will be coming from China.
I’m not sure what the projected consumption of the ESP32 based boards will come down to with a repeater mode but I would assume 2200mAh is a little on the small side for a deployment that could be quite chatty. With that much solar at your disposal you could charge a larger battery to help on those overcast weeks.
With your nodes being relatively close together with good line of sight you may be able to up the throughput using the medium range settings. This makes messaging flow more like what you expect of a service today. I was able to get 100km with the long range settings using moxon’s that weren’t positioned optimally.
You will also likely need some kind of solar charge controller to take full advantage of the 10W panel and directly connect it to the battery. The onboard charge I/C of the Heltec is only 500mA.
Like the idea! The Moxon’s may work for the end nodes but for the ones inbetween like stated above you need something else. Closest I can think of is a simple half wave dipole antenna , has a front back radiation pattern that is equal, the but is “has no gain”. They are cheap however and also easy to make yourself, used on drones a lot too.
The solar panels show as 12/24 volts, the boards need 5v.
Have a 4w 5v solarpanel that plugs into the boards usb. Often not enough sun around here, really need 10w.
My TTGo Lora 32 ( V2.1.6, firmware 0.9.5) lasts about 2 days on a 1500mAh battery, that is with very little Tx.
About the antenas, it makes a lot of sense to have omnis instead of directional for the relays, and making DIY antenas would actually be ideal (lowest price, and ready materials). @PA7John do you have any resources on building such dipole antennas? Are there any other antennas we could DIY?
About energy/solar, that’s a great point about the 10W at 12V, I’m looking now at this 5W 5V panel, but it has the same price as the 10W, is it worth it? To use the 10W I’d need a step-down and probably worth doubling the batteries, is that right?
The 100Km were with a line a sight I assume, right?
You’re all very awesome, thank you once again for sharing your knowledges and experiences!
Hi @luandro – I really dig this project! I’m eager to help think things through if I can, as your project has a lot of overlap with projects I’m hoping to try out myself …
I don’t have any particularly useful input yet I don’t think – but, if you haven’t seen Andreas Spiess’ stuff on Youtube, it’s all really nicely done, and he has all sorts of useful tutorials around LoRa ranges, antenna design, etc …
Found that 5v panels are usually more expensive then 12v in my area.
Looking at your 5v panel it has a build in usb convertor, that will need some waterproofing!
There are panels that output 5-6 volts directly
Considering the remote location in general you want as few points of failure as possible, or as few components as possible?!
The Swiss guy has some good video’s, personally I’m looking into pcb dipoles atm
Many DIY can be googled “868mhz, Lora antenna, etc” have a look and see if there is something that suits the project, also omi directional builds
Very good point @PA7John. Any tips for waterproofing? Silicon around it?
For antennas I’ve been looking at this tutorial for building omnis. I’m guessing they would be the ones with most gain, is that right? Seems like an art, but with enough practice I think we can do it.
Frequency 915 MHz
Latitude -8.39175535 °
Longitude -47.74225488 °
Latitude 08° 23’ 30.32"S
Longitude 047° 44’ 32.12"W
QRA GI61DO
UTM (WGS84) 23L E197990 S9071337
Elevation 272.5 m
Base Antenna Height 1 m
Base Antenna Gain 3.5 dBi
Base Antenna Type omni
Base Antenna Azimuth 0 °
Base Antenna Tilt 0 °
Mobile Antenna Height 2.0 m
Mobile Antenna Gain 3.5 dBi
Tx Power 0.01200 W
Tx Line Loss 0.0 dB
Rx Line Loss 0.0 dB
Rx Threshold 0.220 μV (-120.2 dBm)
Required Reliability 60%
Strong signal margin 10.0 dB
Weak signal field 12.8 dBμV/m
Strong signal field 22.8 dBμV/m
Weak signal covered area 502 km2
Strong signal covered area 220 km2
Weak signal population reached 1032 pop
Strong signal population reached 454 pop
Landcover used Yes
Two rays method used Yes
Radio coverage ID RM7FEA1377749C_2
Generated on 9/1/2020 4:36:06 PM
I probably gave up on 915MHz. And I chose a lower frequency, not higher than 433 MHz. Without very high-quality and sophisticated equipment, you will not get a normally working antenna in a frequency of 915 MHz and all the energy will simply heat the equipment instead of flying in the right direction. At 433 MHz, there is a hope that you will buy or make a working antenna. And of course you need to raise the repeaters as high as possible, the trees absorb these frequencies very efficiently.
@skyde that’s interesting. It seems I can find LoRa boards on 433Mhz as easily as I can find 915Mhz here, would just make the T-Beams I already have useless for this specific experiment.
This would be a big change of plans, can someone else confirm changing to 433mhz would be a better idea? @geeksville@PA7John@dafeman@sam_uk
This will happen in a savanna region, so I’m hoping trees won’t be a huge problem for now. But in the future I intend to implement such networks in the amazon, which will have big problems with trees.
50km is quite achievable with direct line of sight. In your settings you have your TX power set too low. It should be 0.10000W. Rx Threshold can be set to 0.035uV to correspond with -136dBm. Your base antenna will likely be higher than 1m (up on a pole I assume) and if you get those big collinear antennas they are 5.8dBi.
I’m thinking on a good day with EByte E22-900M-22S radios, 5.8dBi antennas and direct line of sight we will see 150km+.
I’ve never used 433MHz to compare to 900MHz sorry. I guess on paper it should achieve better results. However there is greater abundance of 900MHz products around.
The Heltec I was looking at uses a XS1278 radio, also found this TTGO LoRa V1 which uses the SX1276.
Update: These TTGOs with Lora+Gps+baterry just showed up. I’m guessing they are always the best choice? With these and a 5w 5V panel I have a kit ready for deployment, correct?
I can’t say for sure. I’m starting to think we should work on a device spreadsheet in the wiki.
In some cases there will be a trade off between low power and higher transmit range.
In some areas there are rules on transmit power, that may or may not be enforced. Each use case will be different. Maybe in a remote area with little risk of interference (especially if you are likely the only one operating devices in that freq range) transmitting higher than what is legal may be worth it to make a repeater reach remote areas but I strongly suggest using that as an option of last resort.
