ISM Communications for Arduino

If you want to wirelessly communicate between devices, WiFi and Bluetooth are obvious choices. But there’s also the ISM (industrial, scientific, and medical) band that you use. There are inexpensive modules like the SX1278 that can handle this for you using LoRa modulation, but they haven’t been handy to use with an Arduino. [Jan] noticed the same thing and set out to build a shield that allowed an Arduino to communicate using LoRa. You can find the design data on GitHub. [Jan] calls it the LoRenz shield.

According to [Jan], the boards cost about $20 to $30 each to make, and most of that cost was in having PC boards shipped. LoRa lets you trade data rate for bandwidth, but typical data rates are fairly modest. As for range, that depends on a lot of factors, too, but we’ve seen ranges quoted in terms of miles.

Depending on where you live, there may be legal restrictions on how you use a radio like the SX1278. You should understand your local laws before you buy into using the ISM bands. We aren’t sure it would be wise, but the board can coexist with three other similar shields. So you could get 4 radios going on one Arduino if you had too and could manage the power, RF, and other issues involved. The breakout board the module uses has an antenna connector, so depending on your local laws, you could get a good bit of range out of one of these.

[Jan] promises a post on the library that makes it all work shortly, but you can find the code on GitHub now. If you look at the code in the examples directory, it seems pretty easy. You’d have to sling some software, but the SX1278 can support other modes in addition to LoRA including FSK and other data modulation techniques.

We’ve seen other LoRa shields, but not many. If you are interested in other wireless technologies, we’ve talked about them quite a bit. If you want a basic introduction to LoRa, [Andreas Spiess’] video below is a good place to start.

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Two Great Radios Taste Great Together

[Johan Kanflo] sent us his latest recipe: a blend of one part RFM69 sub-gigahertz radio transceiver with one part ESP8266 module. The resulting dish looks absolutely delicious!

We’re all charmed with the ease of use that the ESP8266 brings to the table — plug it in and you’re talking to your existing WiFi network — but we hate the power consumption for battery-powered applications. WiFi is a power hog. And although ISM-band radio modules make point-to-point communications cheap and power-saving, getting them to talk with your computer takes an adapter.

So [Johan] combined the two radios and made a sweet ISM-radio-to-WiFi bridge. His demo application takes whatever data is sent over the ISM band and pushes it to an MQTT broker on his WiFi network. Hardware and firmware are up on GitHub.

We’ve been wanting a device like this for our home network for a while now. Kudos, [Johan] for making it so easy!

Wireless sensors without a microcontroller

While cruising the Internet one day, [Raj] found a really cool pair of RF transmitters and receivers manufactured by Dorji Applied Technology. These modules – the DRF5150S and DRF4432S – work just like any other ISM band transmitter receiver pair with the addition of inputs for analog and digital input pins. [Raj] put together a tutorial for using these radio modules, perfect if you need a very simple wireless connection for your next project.

[Raj]’s tutorial for using the Dorji sensor modules shows the transmitter has two operating modes. The first mode is a simple data transmitter, connected to a microcontroller through a UART connection. The ‘sensor’ mode doesn’t require a separate chip; the on-board STM8L151 microcontroller reads analog values on two pins and sends them over the air to the DRF4432S receiver module.

After programming the transmitter to function as a wireless sensor with an app released by Dorji, [Raj] plugged the transmitter into a breadboard with a battery and digital thermometer. The receiver module is plugged into a USB -> UART module, and data is pulled down from the sensor in a terminal.

[Raj] wrote a small app in Processing to display the data coming from the sensor. He has a wonderful animated thermometer showing the temperature reading of the sensor, the battery voltage and the strength of the wireless signal. Pretty easy, and a very helpful tutorial if you need an easy way to build a wireless sensor.