Meshtastic is a wonderful project for creating decentralised text-based communication networks for local communities using low power (and low cost) Lora radios. Fun fact — the Meshtastic logo appears to reference the chirp modulation used by Lora.
The best way to learn about the project is to explore the forum, join the Discord server and the Reddit community, follow #meshtastic on Twitter, Instagram and on your ActivityPub network of choice, and find recent videos on YouTube.
There are various community efforts to build local networks already:
- Meshtastic Ukraine with around 400 active nodes in the 433 MHz range.
- Austin Mesh in Texas, USA with weekly Friday check-ins (also available globally through the MQTT gateway).
- Iffy Books events and resources (including this incredible zine about Meshtastic).
Network Map
Here is a map of all active nodes connected to networks that relay messages to the official MQTT endpoint. This map is created by a forum user and shared in this thread.
How to Build a Network
Following the learnings from the solar-powered Raspberry Pi security camera project, I want to build solar-powered repeat nodes (with REPEATER role) to place in high enough places to enable coverage for everyone in the area. Since repeat nodes are invisible to the network and can’t send health or sensor data, another node with SENSOR role would be connected to the same battery and would broadcast the health of the repeater node along with temperature and humidity at very long intervals for maximum power savings.
I’ve decided to use Heltec WiFi Lora 32 (v3) ($20, schematic diagram) for the repeater nodes as they use ESP32-S3FN8 for the main controller and SX1262 LoRa chip with an IPEX1.0 antenna connector. This type of connector is really practical for bringing the antenna outside of the enclosure as the larger SMA connector cables are usually harder to bend and require more space in the case.
It also features a TP4054 charge controller and a voltage divider connected to an ADC pin for monitoring the battery voltage which is useful for telemetry. I’ve yet to figure out if it has any over discharge protection.
It is reported that RAK4631 WisBlock Core (similarly priced) with the nRF52840 microcontroller and the same SX1262 LoRa radio uses significantly less power compared to ESP32 devices so it is probably a better choice for pure repeater nodes. However, I wanted something that is more universal with a screen and a case for this prototyping phase.
Power Requirements
There is a great thread on the forum with several posts linking to the following resources that outline the effective power requirements:
- Meshtastic ESP32 airtime and current draws (Google Sheets)
- NRF52840DK+SX1262 Meshtastic airtime/current draws (Google Sheets)
- Meshtastic Power Consumption Tests (Google Sheets)
- How To Calculate Solar Panel and Battery Size (Google Sheets)
The general consensus appears to be that ESP32 powered devices without any bluetooth, screen or GPS attachments need 0.1W on average.
Solar Power
For the initial prototype I found this 4W (D4W) solar panel (affiliate link) with an integrated case for six 18650 battery cells. Using only three cells provides plenty of room for additional electronics like the LoRa board.
In general it is best to oversize the photovoltaic panels significantly to ensure that required charging voltage is reached even when there is low solar radiation (such as during winter).
And here is a close-up of the circuitry:
U3) for charge control, FP6276B (U4) boost controller for 5V output and XB5352A (U5) batter protection chip only for the solar input.Battery Undervoltage Protection
The board appears to use XySemi XB5352A (datasheet PDF) battery management chip U5 (the SOT-23-5 component to the right of the “on” switch) which handles over-voltage (4.30V for VCU with 4.10V recovery VCL), over-discharge (2.40V VDL with 3.0V recovery VDL), over-current (3.2A IOV1), and over-temperature protection. However, this chip is placed on the solar input so there is no under-voltage or over-discharge protection on the battery side.
Configuring the Solar Powered Repeater
And here is the case fitted with Heltec Lora 32 v3 with INA219 connected to pins 41 and 42 (confirmed this with the Arduino Core library and the usage in the Meshtastic firmware) for measuring the battery voltage and current over time and reported over Power Telemetry. Note that simply attaching the device to the board will make the firmware use the INA219 bus voltage reading also for Device Telemetry (which is not documented).
Next Steps
- Document the measured power consumption of Heltec Lora 32 v3 when used as Meshtastic
REPEATER. - Document the device configuration for optimal performance.
- Document the INA219 usage and setup.
Hi Kaspars – this is Will from Austin Mesh – thanks for mentioning us! We have a meeting tonight and I’m excited to keep building out the network. We’ve found that it’s better to over-spec both the batteries and solar panels. Our “version 5.0” solar repeater uses a 12 watt panel and a 6,400 mAh battery (parts list is on austinmesh.org). One of the main problems with the RAK chips is if the voltage falls to a certain level it will put it into a permanent fault state, so it’s best to have a battery that cleanly shuts off power if voltage falls below a certain level. The simpleest way we’ve found to do this is with the Voltaic Systems iot battery packs. The other way we’ve tried is to use a an 18650 battery and use a cutoff chip that shuts power if voltage drops below 4.25v: https://www.etsy.com/listing/1421193059/10-li-ion-battery-protection-modules-pcm
Hey Mr. Martian. Although I am not from Texas (anymore) I wanted to pick your brain if I may. I am very new to LoRa, but I can’t get enough. I am attempting to build a solar powered Lora system. Although my town is so small, if you blink you’ll pass it, I do want to build something for close family. Within 5-10 miles to start with. I have purchased some equipment so far, but I keep getting conflicting designs and I’m totally lost. I was wondering if you or someone you may know, would be able to reach out to possibly help with pointers and what not. I figured maybe email or messenger might be more prompt would bug everyone on this thread lol. With having to order most things from overseas, I’d rather not take 6months to build due to ordering and returning wrong parts and whatnot. Thanks in advance brother.
One thing that I have been unable to find is where to find places to put the nodes. What are legal ways to place nodes in an area to get significant coverage? I live around Wichita, Kansas, which is relatively flatter than most areas of the country, but I’m unsure of how to go about setting up nodes to provide coverage? How do you go about it? Also, I’m using a “hide my email” which is why it looks strange, but this is to keep spam at bay, I hope you understand. I appreciate your time.
That’s a great question. I’m also unsure about this here in Europe. I have the opposite problem of high density buildings and needing to place the nodes on roofs to allow for any decent coverage.
The most practical examples I’ve seen on YouTube and the Meshtastic Discord channel are nodes higher up in mountains placed in wilderness or attached to trees.
ask for forgiveness rather than permission. if authorities somehow manage to identify you as the owner, tell them you’re working with search and rescue to provide a wide-range capable communication network for their teams
Hey Kaspar.
Im currious how many nodes that one repeater can serve ? is it ok for 12 nodes for 1 repeater ?
I appreciate your time.
Personally I haven’t tested this but it should be possible to serve dozens of nodes by a single repeater. The hardcoded limit in the firmware is 100 nodes. However, the air time limits usually are more important — all nodes (including repeaters) are permitted to have a 10% duty cycle (depending on the radio frequency) so a network with lots of traffic can easily saturate that.
Nice node build and website, I recently discovered Meshtastic and started a website and YouTube Channel all about it, a mix of guides and tutorials, news and articles