πŸ’¬ Building a wired RS485 sensor network



  • @wimd
    thank you very much , i test this and i hope this is answer for me. because i am tired really 😞
    thank you my friendπŸ™



  • @wimd
    i test with "PA_HIGH" and "PA_MAX" (for nodes and gateway) but this is more bad.
    (for example for 10-15 meter with 2 wall)
    in default PA for 10 command i have 2 error
    in PA_HIGH for 10 command i have 8 error
    in PA_MAX my connection is disconnect completly
    can you understand where is problem? i think this is related to power supply of radio (because when i want more power for more distance so radio can not have a good connection) but i providing enough power for radio. i use a adapter 5v 2A and connect this to a radio adapter(reglator 5 to 3.3) even use a 4.7u capacitor for radio. similar to photo:
    0_1484474385522_photo_2017-01-15_13-28-34.jpg



  • @Reza You have exactly the same problem as I had when I first found MySensors in march last year.
    I got a couple of radio and started to play with them. All worked fine as long as they were not more than 5m away from each other. I dropped the idea at that time.

    2 months ago I saw the possibility on the website to build a wired network. I started again. With the order for the RS485 bricks I ordered also some radios but now with antenna and amplifier. The only improvement I got was now up to 7m.
    I managed now to connect with my greenhouse that is 12m away but had to place a repeater in between but the connection is no reliable.

    The discussion that is now ongoing is not related anymore to a RS485 network. I suggest you start an new topic specific for your radio issue. Or we both did do something wrong or the hardware that we buy does not meet the specification for transmitting distance.

    Let me now if you started a new topic.




  • Mod

    What are the main advantages of rs485 over I2C bus?



  • @gohan
    I2C bus is designed for short distances, obviously between circuits on one PCB.
    Max allowed capacitance i2c bus is 400pF. CAT5 cable has nominal 52pf/m.
    Ideally you can communicate to distance 8m.
    It is very short bus for home network, I think.
    Or we need some "hacking" for i2c bus, for example at page 4 in this document:

    http://www.nxp.com/documents/application_note/AN460.pdf

    For each node we need one bus expander ( P82B96 ) and two CAN bus drivers ( PCA82C250 ).
    7 + 2*0.5 US$ ( ebay )
    Plus second pair of wires.
    Or buy this: http://mayhewlabs.com/products/i2c-power-extender
    You can read bus length, number of nodes and speed limit, there.

    But, interesting idea.
    With some smart "node addressing" and multi-master i2c bus I can imagine, that on some places you do not need processor.
    For actuator simply use PCF8574 for example.


  • Mod

    So basically for 10-15 meters distance it's better and cheaper to use cheap rs485 modules, right?



  • @gohan
    Yes



  • @wimd thank you friend . i started several topic about this issue , but dont found any answer so i delete all topics. also i dont start new topic because friends are sad for my topics and admin told me dont start any topic 😞
    i have exactly this problem. now for 10 meter i must use a repeater ! for 10 meter ! ! ! ! this is strange ! i use 4.7u capacitor and more. i use radio adaptor. i use reglator module. use 3 type of radio . in sketch use PA_MAX and PA_HIGH ... but effectless. so you told me if i want change my network to wiring with RS485 , i will have same problem again ? i can not found any way for this problem .
    now please let me for read this topic perhaps i can found any way for this problem . thank you



  • @Reza I have written earlier that I didn’t have any problem with RS485 on a cable of 10m but did not trail longer yet.
    If you make trails with the wired network, make sure that you define your node id number

    #define MY_NODE_ID <X>```


  • @hek I was wondering if it could be useful to have an extra sensor that a bridge between the wireless and wire network.
    This bridge is made between the SPI dealing with the wireless network and the hardware serial that is dealing with the wire network.
    It would allow you to connect a remote wired network.

    IF the CE pin for the radio (9) could be user defined, a 2nd thought (based on the bridge idea).
    Can’t something similar be done for the serial gateway and make that one suitable for wired and wireless network in the same gateway?


  • Mod

    Cable will always be better that wireless, so if you can go with cable. I tried NRF24 but with those smd modules I can't get more than 6-7 meters. I have to try to add a longer antenna



  • @gohan
    In some cases 'with cable' is the better option. In some cases wireless is the better option. I totally disagree with you on your statement that cable will be ALWAYS be better than wireless. that's nonsense!

    There are good NRF24 modules out there and there are worse variants, maybe fake ones. I've bought from several ebay stores throughout time. I found out the hard way that some perform good with a 100uF capacitor attached (the simplest variants, costing no more than $0.85), and other perform better with a smaller size capacitor (4.7uF). I get distances with these modules over more than 25 mtrs. with all kinds of obstructions (even faraday alike) in between. All it takes is some (hobby) time to find out what works best (e.g. move a node 1 meter to the left or right or align the antenna somewhat...)
    I never ever modified an antenna, never needed to do so. I once bought 2 nrf24L01+-PA-LNA antenna's for wider coverage as I thought I would need that for better/wider coverage, but now, 2 years later, they still are lying around in my workshop.

    Maybe good to say that these distances can only be achieved with a speed set at 250 kBs and this is only possible using the nrf24L01+ modules!

    If I can, I use wireless, as it is cheap, simple, and convenient, but the best reason for going wireless is that I don't need to use a cable! Simple as that.

    For the sake of staying somewhat on topic ("Building a wired RS485 sensor network")...
    There are occasions in which a wired (RS485) network would be the better choice. In my opinion one occasion is when you need instantly acknowledge that a command really was delivered to a node.

    BR,

    Boozz



  • @wimd
    how long wiring can i use between a node and gateway with rs485 (without repeater)? how many node can support ? delay for send and receive for nrf24 is more or rs485 ? thank you



  • @boozz
    how detect a fake radio with a original radio ?


  • Mod

    @boozz

    I said it's better because in terms of stability and reliability you can't beat cable and I also added that if he can use a cable to go with it otherwise wireless it's still an option, but as you said it takes time and trial and error to make good use of those nrf24 especially for the reason that there are lots of clones on the market that behave slightly differently from one another and thus adding more complexity to the project.
    In addition once you have a cable you can also use it for power.
    Of course cable is not the universal solution for all the problems, but if I had to choose between a wired or wireless security system I'd choose wired and if I would need to have a temperature sensor that reports data every now and then I'd go most likely wireless



  • @gohan
    My reaction was only based on your last post in this tread ☺, I totally agree with you on the wired security system where wireless is not an option.



  • @Reza
    There are many options for detecting fake radio's. For me it works best to test them in a node that has a good working radio attached (preferrably far as far away from its parent node as possible) and exchange it with the suspected fake one.

    There's also a thread in this forum that describes a method to test the quality of nrf24L01+ connections. It's a quality meter. I know for sure you can find this one using the search function.

    By the way; about the wiring distance between a node and gateway: the fastest way to get an answer is to get multiple answers on such questions is using an universal search engine: www.google.com


  • Mod

    @boozz
    What are the codes on the NRF24 chip of the modules you consider being the best performing?


  • Admin


Log in to reply
 

319
Online

7.0k
Users

7.9k
Topics

84.4k
Posts

Looks like your connection to MySensors Forum was lost, please wait while we try to reconnect.