Need wireless switch position indicator - Page 1
Forum section: electronics / general

author: calzap
author_rank: Frequent Contributor
timestamp: June 26, 2023, 09:54:54 pm
content: I need switch position (on/off) indicator that can send data wirelessly at least 500 m. Switches will either be SP switches or relay outputs and are part of a pumping station controller. Absolute minimum is one channel (flow switch) but two data channels (flow switch and motor power) plus “communicating OK” channel would be better. Data update doesn’t need to be any faster than once per minute. Receiver needs to be small enough to carry on a person. A plus would be receiver having an alarm if switch opens. Transmitter can be any size. There will be few trees or buildings between receiver or transmitter. But signals need to penetrate building with outer walls consisting of wood frame with fiber-cement siding and sheet rock interior. Building has lots of windows. Transmit frequency and power need to be legal in the U.S. I have a U.S. amateur extra license but would prefer not to use amateur frequencies.Basically, we want to be notified if the pump shuts down unexpectedly. As it is now, we must inspect periodically and visually.Prefer off-the-shelf equipment but can modify. Any suggestions?Mike in California

author: Kim Christensen
author_rank: Super Contributor
timestamp: June 27, 2023, 12:48:24 am
content: Have a look at something like the Zetron SentriDial which can call a list phone numbers, etc. Or the SentriVoice to trigger a radio.You'd still have to supply the radio link, pager TX, or phone line.

author: Buriedcode
author_rank: Super Contributor
timestamp: June 27, 2023, 05:08:52 am
content: Yeah I'll second a GSM module for very infrequent transmits - get it to send you a text. A prepay sim card will last a long time, and as the transmitter has plenty of power available it'll be fine.The toruble with say, a 315/915MHz system (in the US?) is, you may get the range out of it, but the reciever will have to be constantly listening, which uses up power, which means regularly recharging the portable monitor, where-as every has a phone thats always listening.

author: Berni
author_rank: Super Contributor
timestamp: June 27, 2023, 06:57:45 am
content: GSM does sound like the way to do it if the number of transmitters is reasonably low (since each needs a SIM card)With a large number of transmitters the running cost of the SIM cards and all those GSM modems might add up. So for those perhaps something like LoRA might be better suited. It uses ISM band frequencies and is designed to send small amounts of data at low data rates over long distances while also being low power.If you want to minimize development time you could use Xbee modules with a tiny 8bit MCU next to it that periodically pumps the status out serially. For the receiver side you could use a Android phone that has a USB to serial cable plugged into it that goes into a receiving Xbee module. Then just write a small app that parses the serial data, displays it on screen or makes an alarm. (Oh heck to start with as a proof of concept, you could just use a serial terminal app to print the raw serial data to screen)

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 27, 2023, 01:15:47 pm
content: How about LoRa?

author: calzap
author_rank: Frequent Contributor
timestamp: June 27, 2023, 02:48:18 pm
content: Quote from: NiHaoMike on June 27, 2023, 01:15:47 pmYeah, LoRa or maybe DASH7 should work. Any suggestions on hardware?Mike