TTN Node Dry Contact

Hi all,

I need to build a sensor.
All it needs to do is to register a magnetic reed switch in either n.o or n.c position. Dry contact. No power. Just continuity. Seems like an impossible incredibly expensive offering… People are crazy for the prices they are asking for something like this.

I am assuming the TTN Node can do this? Can I just connect 2 wires to where the button is and when contact is made it registers when the switch closes?

This is going into an existing case. I was wondering if I can purchase just the pc board and not the weatherproof cover.

There has to be a cheaper board/option to do this simple thing? It shouldnt cost 60 bucks a board. More like 10 maybe 20 dollars.

I am greatful for any help.

It’s possible to do this with around $20 worth of parts (for example both Murata and ACSIP offer SMD modules which combine the radio with a suitable STM32L0 mcu), but they still need to be put on a board, and you need a battery or other power source. And tuning the software is non-trivial.

Or you can buy an RN2483 AT-command set module implementing the LoRaWAN stack (or use the similar mode of the Murata module), and pair it with your own processor of your choice to inject configuration and read the switch; that might be a little simpler, but ultimately less flexible and higher cost than running the LoRaWAN stack in your own processor.

Most of the boards being sold have some sensors on them so that they are useful as demos by themselves. Of course you don’t need that, in the long run, but right now, don’t discount the NRE of making a custom board for an idea not yet proven for your application needs and circumstances.

Likely it’s best to get something off the shelf to use as a proof of concept; if the idea works well enough you want it in quantity, then you can approach a vendor to build you a barebones version with the extras depopulated, or you can design your own.

Don’t forget to budget for gateways, unless you are in an area where you know there is coverage.


if you want a cheap easy ready to go solution with outdoor housing.

if you want a cheaper experimental solution, you can try boards with RFM95 tranceiver,

868MHz LoRa Radio Node SX1276 2.4G Wireless Transceiver Board RFM95 For Arduino

Parts wise it shouldn’t. Add the overhead of CE and LoRaWAN certification and suddenly things look different. Oh, don’t forget commercial entities require some profit as well. Looking at TV programs where entrepreneurs rescue failing companies there should be at least 50% margin after finished product. :smile: