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Edited: Jun 18, 2020

RS485 for long distance

Hi Angelo,

I'm studying the installation of your system, but I need to reach relays at "long" distance point (let's say 50 meters, with margin).

Currently, I was testing your project on a desk driving relays on GPIOs, but it is not suitable for my installation.

I think the best way to send commands to this distance is to use RS485.

I was wondering if you already studied this case ?

The idea is to use either a USB dongle

(I have no idea how peripherals connected on USB could be integrated in your project)

or a pi hat (driven through I2C).

If this integration is possible, then it would need a configuration layer with address(and probably a second driver layer to implement required commands of these relays boards)...

I would like to know if you're interested in this integration ?

Another solution for me without modifications of your software would be to add an interface board (arduino ?) to translate GPIO states/edges from your software to RS485 commands. But I think if all can be integrated on the PI board and in your software, that would be a great addition.

PS: links in this post are just samples to illustrate, it needs to be checked for real compatibility

Regards,

Jerome

9 comments

9 Comments

hydrosys4

Aug 14, 2021

For People interested in setting the MQTT, here the guide:

hydrosys4

Aug 14, 2021

Ciao,

Thanks for sharing, this is very interesting. As expected the WiFi at 2.4GHz is quite sensitive to walls and obstructions, anyway in line of sight seems that hundreds of meters are reachable, and this is a good news (Just as note worth to mention, the line of sight in telecommunications usually does not refer to the sight but to the first Fresnel ellipse which should not have obstacles). Also the test with the Dish antenna on router side was very interesting. I definitely did not expect such good results.

In the latest SW version I've developed a solution using the 433MHz (HC-12) transmitter (for sensors) this can exceed above 1km. Below the link.

Long Range Wireless Sensors with HC12, but not LoRa

andrea.milano

Aug 15, 2021

Replying to

Ciao Angelo, I missed the long range wireless post. I just bought a property in south Italy with 3.000sqm of nice soil. This is the perfect solution for distances like 2/300m. Thank you for all your efforts. Indeed.

andrea.milano

Aug 07, 2021

Ciao Angelo, I was looking on ESP distances for other reason and found a couple of interesting videos: https://www.youtube.com/watch?v=7BYdZ_24yg0 https://www.youtube.com/watch?v=KYLN9qH0C84

Will Waterston

Jun 21, 2020

I'm using 24VAC valves, so they aren't so susceptible to voltage drop over distance as are DC devices. If you are using one of those online calculators to determine voltage drop over distance per wire gauge, make sure its calculating for AC, not DC which is more common.

For the ESP there are some higher level programming tools, like ESP Home where you can basically 'add modules' and they write the code for you, not sure

how good or flexible they are, I have never used them.

When I get some time I'll build a project for ESP that can control GPIO via MQTT and publish it, that will give a better idea to our benificent host as to how it might be utilised.

jerome.gombart

Jun 19, 2020

Hi,

thanks for your answers. Different options now...

1. power wires over long distance as you did Will

2. wireless with wifi

3. wires for communication over long distance as I imagined at first.

2 & 3 are more flexible in terms of adding sensors, or more valves etc... 1. is easiest and faster...

I have no experience with ESP8266...

hydrosys4

Jun 19, 2020

Thanks for the feedback.

So in your case there are 30m of cable. Until the voltage drop is kept under certain values nothing prevents the cable to work at any distance.

I ordered a couple of the inexpensive ESP8266, but I never worked with them before, anyway doesn't look so complicate as there are plenty of information on internet.

The devices have a small antenna and I suppose quite low power, anybody has idea what what might be the range of this devices?

The main issue I have with the ESP8266 is that they require "programming Skills" to set them, in particular the WiFi network parameters. This is not so good for my project as the implementation principle is to try to keep things easy.

I'll try to check if the ESP can be directly wired to the raspberry and flashed using the hydrosys4 configuration.

Ideas about this point are welcome.

hydrosys4

Jun 18, 2020

Hi Jerome,

I see the issue there, 50m is quite long. Some time ago I evaluated a similar problem and my conclusion was that wireless was indeed the best solution.

Wireless has itself a whole bunch of other problems but is way more flexible, it does not require long cable installation and maintenance.

Back to your question, I plan to integrate MQTT in my system in the future so to control some Actuators/Sensors in the WiFi coverage range.

For longer range, I was thinking about transceivers at low frequencies like 433 MHz or 866 MHz but haven't had much time to evaluate a good solution.

Regards,

Angelo

Will Waterston

Jun 18, 2020

Replying to

I still think MQTT is the best solution. This way you can have a separate board such as a simple ESP8266 based board which costs next to nothing. The ESP can pub/sub on MQTT and you can interface whatever extra hardware you need onto the ESP, which could be 433, wifi, lora or use the GPIO straight off the ESP.

My situation is similar. I have my valves about 30m away, but the standard 7core irrigation cable driven off the relays seems to work fine at this distance, especially since they are 24VAC powered. However, I'm also looking at locating capacitive moisture sensors at the same distance, I don't know if that will work. But, it would be easy to have the sensors on an ESP and data sent back to hydrosys via MQTT.