Node not working after adding some wires and a capacitor



  • Hello
    This was going to be a post about how one of my nodes suddenly stopped working after I modified the circuit, but I made some measurements and at least I have some guessings to confirm with you.

    My circuit is composed of:

    • Arduino nano clone
    • NRF24L01
    • A button
    • double side protoboard or perf-board
    • some spare wires

    At first the circuit was working perfectly. It was communicating with the gateway almost instantaneously. Then I decided to wire some pins and connect them to some "spike connectors" on another part of the board and I also realized that I forgot to connect a capacitor so I connected a 16v 47uf capacitor.
    After that I started to get some errors on communication. The gateway was able to see messages coming from the node, but the node was not seeing the answers back.
    I made some test with similar arduinos using jumper wires and the same gateway and everything was still working.
    Then I made some measurements on the failing node, and I saw that the radio was getting 3.226v
    I made some more measurements on the other working arduino and the radio was getting 3.447v. So I think the problem is the voltage drop. I took the arduino apart, without any radio or anything else and it was still output 3.2 volts on the 3.3 volts output.
    What can be motivating this ? I worked perfectly for an entire week, so I don't know what could be happening.

    Thanks in advance.


  • Mod

    @danielo-rodríguez Supply range for nRF24 according to the datasheet is 1.9 to 3.6V, so you are in the safe range.
    Maybe one of your jumper wires has a bad contact?


  • Mod

    @danielo-rodríguez the new wires, were they added close to the nrf antenna? Could you post a photo of your board. Having anything conductive close to the antenna can have a bad effect on transmission and reception.



  • @mfalkvidd I was to provide pictures yesterday, but my post was being moderated and I was not able to update it. Happy to provide them now:

    wires
    board
    back

    Something important to note is that, yesterday making the tests again all other nodes were failing with the same problematic. I'm starting to think that has some randomness on the gateway involved... but then why it sometimes works for some nodes but does not work for other nodes?
    I'm using a wemos D1 mini as gateway.


  • Mod

    @danielo-rodríguez with that much stuff almost touching the antenna, transmission will be very bad.

    There should be at least a few centimetres free area around the antenna. Easiest way to check is to put 1-2 extra headers for the nrf (to get it higher up) or to use dupont wires instead of the header.



  • @yveaux said in Node not working after adding some wires and a capacitor:

    @danielo-rodríguez Supply range for nRF24 according to the datasheet is 1.9 to 3.6V, so you are in the safe range.

    Thats good to know, thanks for that information.

    @mfalkvidd said in Node not working after adding some wires and a capacitor:

    @danielo-rodríguez with that much stuff almost touching the antenna, transmission will be very bad.

    Oh, that is a good point. What I'm going to do is to take some jumpers and move them away to see if that makes a difference.
    What would you say about putting the antena in the other direction (upwards). Would that be good enough?



  • This is what I did:
    Imgur

    I'm still get the exact same errors... I'm starting to thing that it has something to do with the gateway. Maybe I can try to build another gateway using an arduino instead of an esp8266? Do you have any sketch that I can rapidly test?

    And here is a picture of my gateway
    Imgur


  • Mod

    @danielo-rodríguez thanks for posting the photos.

    I see that the nrf24 on your gateway is the variant with the "blob" instead of a chip. If the radio is in a socket, try replacing it with one that has the chip. The clones with the blobs seem to have worse performance, judging by reports here in the forum.

    The antenna on the gateway is pretty close to the metal in the protoboard. Some extra distance could be good, at least to check if the protoboard is messing with the signal.

    Does the gateway nrf have a capacitor to stabilize the power supply?

    https://www.mysensors.org/build/serial_gateway has a sketch for a serial (usb) gateway if you want to build one.



  • @mfalkvidd thanks again.

    @mfalkvidd said in Node not working after adding some wires and a capacitor:

    I see that the nrf24 on your gateway is the variant with the "blob" instead of a chip. If the radio is in a socket, try replacing it with one that has the chip.

    I have several of both, I'll try to put one of the "good ones" on the gateway to see if that makes a difference.

    @mfalkvidd said in Node not working after adding some wires and a capacitor:

    The antenna on the gateway is pretty close to the metal in the protoboard. Some extra distance could be good, at least to check if the protoboard is messing with the signal.

    The picture is taken from above, and seems the antena is quite close to the board, but in realyti it is not that bad. I'm posting here another image to show how far it is from the bottom. Also you can see that there is a capacitor attached (same values as the node)

    Imgur

    What disturbs me the most is that it worked for an entire week, then just some nodes and now anything works. This is kinda crazy...

    Thanks for your help, I'll try with your suggestion of changing the radio



  • Your NRF is 2.4GHz. Your Wemos and home WiFi network is 2.4GHz too.
    Maybe your WiFi router randomly switch wifi channels to the chanel of your NRF network.
    Try set fixed channel on your router.



  • @kimot said in Node not working after adding some wires and a capacitor:

    Your NRF is 2.4GHz. Your Wemos and home WiFi network is 2.4GHz too.
    Maybe your WiFi router randomly switch wifi channels to the chanel of your NRF network.
    Try set fixed channel on your router.

    That is a good and smart advice, however:

    • My router is already set to fixed channel 11
    • My router is on my bottom floor while I'm doing my tests on my first floor. Maybe the interferences are not that bad? Probably I just said a stupid thing
    • I have the following on my nodes and gateway: #define MY_RF24_CHANNEL 80 and since 80 is not even an available channel on wifi (not at least on my router) it should be fine even if it were not fixed

    But I appreciate that you pointed it out.

    Now I have good news that doesn't feel good. I did what @mfalkvidd suggested and I swapped the radio on the gateway with a version without the blob on the chip. After that everything has been working flawlessly. All my test nodes work without any problem, the ones using good radios and the ones using the radio with the blob. They all work, not a single drop. Sometimes if I touch the radio with my hands, I can see a error appearing !TSF:MSG:LEN=8,EXP=7 but does't seem to affect the operative of the module.
    Why does this feel bad? Because I was on a similar situation a week ago, where everything was working perfectly for an entire week and then everything started to fail so, how do I know this is not going to fail in a week? I can't

    Now I have to experiment without fixed IDs. I never got it working using automatic IDs and I can't understand why. At first I thought it was because I didn't had a "join mode button", but seems that such button has a totally different usage. If somebody could explain me how that button is supposed to work and if it is required for dynamic IDs to be assigned I will be also very grateful.

    Regards.


  • Mod

    @danielo-rodríguez said in Node not working after adding some wires and a capacitor:

    I never got it working using automatic IDs and I can't understand why.

    You need a controller (next to the regular gateway) to hand out the IDs. Do you have one?

    As a side note, nrf24 channel 80 maps to 2.480ghz, which is pretty close to wifi channel 11. Depending on your wifi access point settings, these may interfere.



  • @yveaux said in Node not working after adding some wires and a capacitor:

    @danielo-rodríguez said in Node not working after adding some wires and a capacitor:

    I never got it working using automatic IDs and I can't understand why.

    You need a controller (next to the regular gateway) to hand out the IDs. Do you have one?

    Oh, that is completely new information for me. Yes, I have one, but I don't have it setup. I think the IDs was something particular to mySensors. Will this work with home assistant?

    As a side note, nrf24 channel 80 maps to 2.480ghz, which is pretty close to wifi channel 11. Depending on your wifi access point settings, these may interfere.

    Wow, that makes me look like a fool 😅
    I'll try to change to another channel then. Which would be a good fit? is there a range that is better to keep, like 3-2 channels or being just one channel away will be enough?


  • Mod

    @danielo-rodríguez said in Node not working after adding some wires and a capacitor:

    Which would be a good fit?

    It depends on your environment. In rural environments you could try the lower channels.
    The higher channels (around 100 and up) are outside the wifi range, but I've seen clones performing worse at high frequencies.

    As a reference, this post discusses Wifi vs nRF24 channels: https://forum.mysensors.org/topic/4721/nrf-frequency-and-channels


 

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