Looking for simple LoRa Tx/Rx combo to indicate switch position - Page 1
Forum section: electronics / projects

author: calzap
author_rank: Frequent Contributor
timestamp: April 30, 2025, 07:03:32 am
content: Looking for a LoRa transmitter that can indicate when a switch is in the on position (will actually be NO contacts of a relay). If necessary, any voltage can be supplied via the contacts although detection of closure w/o voltage would be simplest. Will wire a test switch in parallel. Transmitter will be in a fixed location. Just about any voltage is available to power the transmitter.Receiver just needs to sound a buzzer and turn-on a LED when signal of switch closure from transmitter is received. Needs to have power and silence switches. And should be portable and lightweight so it can be moved around. Pocket size would be ideal. Obviously needs to be battery powered. Low battery indicator would be a plus, but simple power-on LED is OK. Distance to be up to 300 m. Frequency must legal in the U.S. I can take care of case, switches, buzzer, battery holder and LEDs.Suggestions?Mike

author: JoeyG
author_rank: Regular Contributor
timestamp: April 30, 2025, 09:50:37 am
content: LoRa or LoRaWAN?LoRa is the RF modulation scheme - LoRaWAN uses LoRa RF modulation scheme as part of the RF network protocol where end nodes connect to a LoRaWAN gateway.What your application receiver /gateway?902-928MHz has some government FCC hopping restrictions any modulation scheme has to be compliant to.

author: voltsandjolts
author_rank: Unknown
timestamp: April 30, 2025, 09:52:08 am
content: Wireless doorbell?

author: SteveThackery
author_rank: Super Contributor
timestamp: April 30, 2025, 10:24:04 am
content: Quote from: voltsandjolts on April 30, 2025, 09:52:08 amInteresting you mention that. I've used the guts of wireless doorbells for various roles in the past, including sending a time signal to various slave clocks around the house. They are a cheap and convenient way of sending basic signals over short distances.HOWEVER, I don't think many of them have a 300m range, so probably not suitable.Another issue is that none of the wireless doorbells I've used send a "button released" signal, so you might have to arrange for it to send a "pressed" signal every few seconds while the switch is operated, and the remote receiver infers a "released" signal when the signal has stopped for longer than a few seconds.

author: BadeBhaiya
author_rank: Regular Contributor
timestamp: April 30, 2025, 10:49:40 am
content: I may be incorrect, but I don't think you can buy LoRa Rx-Tx pairs like you can with 433MHz/868MHx OOK/ASK modules.afaik LoRa modules are almost always transreceiver chips that you need to operate using a microcontroller.

author: fchk
author_rank: Frequent Contributor
timestamp: April 30, 2025, 10:53:17 am
content: Quote from: calzap on April 30, 2025, 07:03:32 amI'd suggest using LTE. A Pi with LTE hat would be the transmitter - sending messages on timer or on change. Your phone would be the receiver.

author: dzwer
author_rank: Contributor
timestamp: April 30, 2025, 11:53:07 am
content: Quote from: BadeBhaiya on April 30, 2025, 10:49:40 amEvery LoRa module on market can transmit and receive messages!You can buy 2 modules and configure them to work on only one frequency for Tx and Rx.One module will be your switch - Tx.The other module will be your receiver - Rx.Implement on the Tx side to expect confirmation from the Rx side with N-repetitions, but if you are on DR0/SF12 you will cover 300m very easy.If implemented properly, the transmitter can work on batteries for years...The receiver should work in Class C where the average consumption is about 10-15mA.For the receiver you will need a proper rechargable battery.Here is all in one solution:https://lilygo.cc/products/t-beam?variant=42204035154101

author: calzap
author_rank: Frequent Contributor
timestamp: April 30, 2025, 03:36:33 pm
content: Thanks for the replies so far. I thought of a wireless doorbell. I could do latch circuits on transmitter and receiver. But the range is too short. Looks like using the LoRa modules by Lillygo would work, but they appear to be designed for use by someone already experienced with LoRa and MESH with poor documentation and steep learning curve for beginners.I would only need one reception on the receiver and would then go to the transmitter to reset. The setup is to provide a wireless signal when the trouble LED lights on an irrigation pump controller. When the signal is received, a person must investigate and would reset the transmitter. In other words, it’s a one-shot episode for each transmit/receive event. The setup would be used about every fifth day during six months of the year.It may be the simplest approach will be to mod one of a pair of FRS transceivers. I can have the pump controller LED circuit activate transmission on one transceiver … many have a bell tone button which could be rewired. I think some have a corded push-to-talk button, which would make things even simpler. Because the receiving transceivers would not be modified, multiple persons could carry them.Mike