re: Which one of you made $10k last month mining Helium?

My Helium miners won't be here for a long time, so in the meantime I picked up a Mikrotik LoRaWAN gateway that works with TheThingsNetwork (TTN) to get my feet wet with building nodes.

I used an Arduino Pro Mini and a HopeRF RFM95W radio to do my testing/prototyping. My test node is currently out in the back yard reporting the temp, humidity, and battery voltage in 5 minute intervals.

LoRa has a range measured in miles, but that is with optimal conditions... outdoor gateway with high gain antenna mounted as high as possible, high gain antenna on the node, line of sight, etc. My gateway is the cheap indoor variety, small low-gain built in antenna, my node's antenna is just a piece of wire, and it's outside with several walls and a building blocking line of sight, but it's still sending data just fine.

I was able to fit temp, humidity, battery voltage, and a test value all into just 8 bytes, so transmission times are very low. Airtime is reported as 370ms per message, and I'm not sure how long it takes to read the weather sensor but I believe total wake time is less than 1 second per 5 minutes. It has been running on battery for a couple hours, and it looks like it has lost about 0.01 volts in that time, but most of that could just be error. I'll have to give it a couple days to estimate total runtime a little better. It is also just a 1,000mah lipo battery pack, so I could swap that out for 3 AA's and get 5-10X more battery life. I also removed the pro mini's power LED because it draws a lot of current, even during sleep mode.

There are quite a few details that need to be just right to build a DIY LoRa node. It took me a while just to find a good sample sketch to work from, and even after that it took me a while to figure out that I needed to adjust the radio channels it was using. I had the right channel plan (US 915mhz), but you then have to choose the right sub-band. I read a bunch of pinout charts and example circuits to wire up the radio. You have to snip the antenna just the right length (3-1/16"). There are tons of pre-built nodes that are basically plug and play, or breakout boards to make a DIY build easier, but I went the breadboard route as I tend to do just so that I could learn as much as possible.

On the network side, you have to write a function to unpack your message. It involves bit-shifting (which I still don't quite understand) to convert the received hex into decimal values, and then you package them up into a JSON-style object. From there you have several integrations to choose from, so you can send your data to the TTN cloud storage where you can retrieve it via HTTP endpoint, or you can send it to AWS IoT, or MQTT, or a couple other options. From there it's up to you how to process it further. Maybe you write a web/mobile app to consume it. Maybe you hook it up to home assistant and do some automations with it. Whatever.

So now that I have a basic node platform, I can put together pretty much any type of sensor I want pretty quickly and cheaply. Check the weather like I've done, soil conditions, battery status (like on a generator, boat, sxs, whatever), gps location, door/window/gate status, water level, vehicle presence, PIR motion, vibration/accelerometer, light level, tank/container level, etc. Anything you want to measure, you can do it hundreds of times per day for like $20 in parts. And you can cover dozens or hundreds of square miles with just 1 cheap gateway.


Crazy stuff, and it's fun.