Just like to know why nrf on cheap booster fails



  • Hi guys.
    My setup is EasyPCB board with 2AA batteries with booster and one dallas sensor on D3. Radio is NRF24L+.
    With this setup and new batteries, the node has no problem connecting to GW. But as soon as battery drops or I connect a soil moisture to it its having problem connection to GW. Could anyone with more knowledge of electronic try to explain why this is happening.
    The thing is that after 5-15 tries it can suddenly register. Why then and not first time.
    Read a lot of stuff that radio is sensitive and you should not run it behind a booster, Why? What is it that happened then, all logic in my head says 3,3 V is much better then 2,5.
    I do lack electronic knowledge so please enlighten me
    Big thx
    /Håkan


  • Mod

    @keldandorin most boosters will not deliver a clean 3.3V output. So when the nrf consumes power to send, the voltage drops quickly. The nrf is extremely sensitive to voltage drops.

    So yes, 3.3V can be better, but only if it stays at 3.3V.

    I took the liberty to modify your topic subject to something more explanatory.



  • @mfalkvidd OK got that but how come it dosent connect when soil sensor is connected and powerd directly from battery. If I disconnect soil sensor it connects directly. How can that sensor "disturb" radio module?


  • Mod

    @keldandorin the key in what I wrote is extremely sensitive.

    That means anything can disturb it.


  • Hardware Contributor

    @keldandorin i might be wrong here... (and im buying myself a Oscilloscope to learn more about this exact issue and how I can make EasyPCB even better) but my theory will at this point be that when the Soil sensor is on, you consume more current which goes through the booster, which in its turn due to more work makes more noice.

    And also as @mfalkvidd said... the sensor itself can disburb.
    If you search relay you will find alot of issues where the relay will disturb the radio as well.



  • @sundberg84 said in Just like to know why nrf on cheap booster fails:

    e.

    So what you saying is that the Noise is something that disturb the radio frequency or is it more the signal from Arduino to radio?
    Sorry for all N00B question but this annoys me not knowing 😊


  • Hardware Contributor

    @keldandorin - i think its a power issue, when the booster is regulating the power back up to 3.3v it introduces noice (small fluctuation in the electrical signal/voltage) into the circiut which affects the power (and therefore the function) on the radio.
    It could also be as you said, a noice field which disturb the radio RF signal.

    Im not an expert here, but im will try to gather as much info as possible and post good advice as soon as I have a Oscilloscope).

    Some more info: https://en.wikipedia.org/wiki/DC-to-DC_converter

    Although they require few components, switching converters are electronically complex. Like all high-frequency circuits, their components must be carefully specified and physically arranged to achieve stable operation and to keep switching noise (EMI / RFI) at acceptable levels



  • @mfalkvidd Booster is not always the issue here, had the same issue when trying use my Rpi3 as a GW. None of my nodes was able to conenct the first 5 tryes so I bought a NodeMCU insted to us as GW. Looks like there is newer and more expensiv NRF modules to, Like this one http://www.elecfreaks.com/estore/nrf24l01p-pa-lna-v3-1-rfm05.html and I think as long as power dosent drop under 1.9v it should be able to send atleast acording to spec.


  • Hardware Contributor

    @keldandorin - ok, good to know... booster can be an issue since its related with power.

    The nrf-chip is known to be really sensitive as @mfalkvidd said... capacitor is a must!
    With the pa/lna version you need a good (and strong) power supply.

    I have had several radios which couldnt connect at all because it was a bad clone.
    If you want to be sure, order a genuine device from a known shop.



  • @sundberg84 I dont run the nrf wia booster at the moment. Can the booster still be a issue then? btw have a 4.7 cap conencted


  • Hardware Contributor

    @keldandorin - No, if you dont have a booster its not a problem :)


  • Hero Member

    No offense intended, but the OP question could be rephrased to be "Why is my cheap booster setup a piece of garbage?" Honestly, how can anyone know the answer to that question given how little information is provided in the OP? For all we know he could be using an unmodified joule thief circuit--with all kinds of ringing--meant to power LED's on a Chinese solar garden lamp from the dollar store and wondering why it doesn't work.


  • Hardware Contributor

    like advised above, radio modules doesn't like so much switching converters (boosters stepup, or step down). In the best cases, it can remove a few db of the radio sensitivity, or more.

    RPI power supply is not very clean too if i remember. the same for some computer usb.

    LDO are better regarding this, due to their construction, but are less efficient than some switching converters.
    What can help in general, is filtering directly after the switching power supply (using ferrites and capacitors), and add a few capas close to the radio.

    For some ideas about improving pcbs.. , for rf etc, it is better to have a strong, wide, uninterrupted gnd plane/ counterpoise, not too much angle on the transmission line to antenna else it could act like a RF short.
    Things like that can reduce rf efficiency, shift freq etc..
    That's why it's often easier to get better rf perf with 4layers board. And also i think the easiest way to reduce EMI etc (the same applies to AC stuff). Else rf pollution begins :grin:
    For more infos, lot of infos on google.


  • Hardware Contributor

    @scalz - agree, there are many PCB (RF) designers which suggest 4 layer board (and I think its the best)... but the price!



  • @sundberg84 What can then make the radio not connecting when adding a soil sensor and as soon as you disconnect it node connect to GW.


  • Hardware Contributor

    @keldandorin - im sorry, I think we need to start over and I was not clear enough.
    To be able to help you without guessing (as I did above) please describe your problem a little better.

    Go through https://forum.mysensors.org/topic/666/debug-faq-and-how-ask-for-help/ and see if that can help you. If not please post the questions posted in the topic "How to ask for help" and im sure we can all help you much better.



  • @sundberg84 HEHE no problem I'm not that clear in my questions ether.
    Let me describe my setup. Easy PCB (yours) revision 8.
    Running on battery, NRF powered directly by battery (no booster there) Booster running Arduino and sensors. Caps and stuff is there, I have just made a copy of your setup. Think I even used all your links for shopping list to 
    If I have one sensor connected DS18b20 pin 3. No problem with radio connecting to Gateway.

    If I add a second (soil Moisture) sensor on pin 4 the node gets problem connecting to GW. Sometimes it takes 5-10 tries and it connects sometimes never.
    So where is the problem here, Power to NRF is the same (good new battery’s 3.2v) Tried some setups where I put nrf at a distant from soil Sensor, same problem.
    If I disconnect soil sensor it will connect at the first try again.

    So what in the setup can disturb the radio/NRF so it has problem connecting?
    If running NRF via booster it makes sense that the booster can add noise but when you not running nrf through booster what can then be the source for noise?

    My next step in founding this out is to by some more expensive/better booster,NRF and so on to found out the problem. Sins my experience in electronic stuff is based on what you learned in school I do have a lot to catch up on 
    Thx for any ideas what to try or do to figure this out
    //Håkan

    ps. gone through trubbelshooting guide several times :)


  • Hardware Contributor

    @keldandorin - ah, ok - but you still have a booster in the circuit even though its not connected directly to the radio. They (booster + radio) share a common ground for example and there are EMI to consider.

    The answers above stand valid - as soon as you add something new to the circiut you change everything. The booster will need to provide more output and this can change the noice.

    My suggestion would be to remove the booster and bridge Vin - Vout (on the booster pins) with a wire, add the soil sensor and watch the results.


  • Hero Member

    For mitigating EMI/RFI, what I've found generally helps the most is: keep wire and trace lengths as short as humanly possible.

    Usually that alone fixes it. Try that first. If still failing, add decoupling caps if the design doesn't already have them.

    There's a whole litany of other things to try that might help, but they tend to be hit or miss.



  • @sundberg84 Ah you see I need to learn more :) Didnt know that gnd could add noice. Will try what you sugests thx Håkan


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