💬 Connecting the Radio

[mfalkvidd]

@manutremo the speed of electromagnetic waves is slower in metal than in vacuum, that's why the length is shorter.

My experience is that the length doesn't need to be exact, but antenna theory is way too complicated for me to understand the details.

[manutremo]

Many thanks @mfalkvidd . That explains it.

While waiting for an answer I also found some sites which mention that the speed of electromagnetic waves is even slower if the conductor has an isolation layer around, which would further justify the difference.

Many thanks! :+1:

[mfalkvidd]

@manutremo I think that part is due to skin effect.

[manutremo]

@mfalkvidd Many thanks again... I learn new things every day.

[gvorster]

@manutremo said in 💬 Connecting the Radio:

I have one question regarding the length of the 868MHz antenna. According to the theory, a the wavelength of a 868Mhz signal is 300/868 = 34.6 mm, so a quarter wave antenna should be 8.6mm long. The table above indicates 8.2mm. May someone confirm the correct figure, and also indicate how critical is that difference in terms of range?

I tried 3 types of antennas with RFM69HCW 868mhz.

1. Just a 8.6 cm wire

2. helical antenna

3. sma antenna

Indoor in my appartement (one floor) it doesn't matter which one I use. All is working fine.
I tried 2 nodes in my metal mailbox 10 meters below which has 2 tiny holes.
One with helical antenna, one with sma antenna.

Gateway (using sma antenna) receives no data.

Testing two repeater nodes (1 helical, 1 sma antenna) near a window I receive data via both repeaters. Sometimes the repeater with sma antenna is not relaying messages for the node with the sma antenna.

In my situation, the helical antenna works better for me. I just buy them on ebay.

[gohan]

Maybe the sma antenna is for the wrong frequency and it's giving poor results.

[krisha]

There is a mini module of the NRF 24L01+. Unfortunately some pinouts on the web were not correct. Not sure if many people use that, but here is a pinout that worked for me: http://s2.electrodragon.com/wp-content/uploads/2014/12/NRF24-Mini-02.jpg

[manul]

Hi Team,

First of all, thank you for your amazing work! It does help a lot to sea a dream become true :)

I was wondering, it seems that I can't receive messages from NRF24 radio while arduino node is sleeping... I've read several testimonies in this way as well on forums. I did connect the IRQ of the transceiver to the PIN 2 of my arduino, and took this as event for exiting sleep mode, but it seems not to work.

Is there anything in the roadmap regarding this? It could be really amazing to be able to sleep the battery-powered arduino, and wake it up as soon a message is received by the radio.
Or maybe there is something I did not correctly. Is there a feature for this?

[mfalkvidd]

@manul it would indeed be amazing, but the radios consume so much power when listening that it is no use to sleep the mcu.

The smartsleep feature is the best alternative so far. documentation: https://www.mysensors.org/download/sensor_api_20#sleeping

[ricorico94]

Hi,
I'm interested in using long range sensors based on LoRa and I saw on this forum that LORA radios should be supported with the RFM95. But I did not see any explanation or advice on hardware, pins, etc.
Could anyone confirm that the type of radio to attach on the gateway and the sensor is like:
link to aliexpress RFM95 radio

I see the chip mentioned is "RF96", but I did not see that name on the forum..(it was SX1276 I think), so I don't know.
Regarding frequency, I uderstood from other websites that in France, the frequency should be 868MHz, correct ? No risk to interfere with EnOcean/Zwave devices ?

I see also that these RFM95 radios have many more pins than the NRF24L01 : should I use the same pins than for NRF24 and leave the others unused ?
and then in the sketch, use the #define RFM95 statement ? Is it all that simple ?

And then I install the RFM95 as a second MySensors gateway on my network (for instance as an ethernet gateway) ?

br,
Ricorico94

[peerv]

Hi ricorico94,
If you are interested in LoRa and how to connect the radio have a look at www.thethingsnetwork.org

[MattiMan]

Hello!
I would like to use NRF24+PA radio, but when I try to use it instead normal NRF24 radio in MQTT-gateway it just dont work. I cant make connection between sensors and gateway.

Normal radio works just fine, but the range is a bit short for me.

I tried the low power setting also, but no help.

What should I do to make it work?

I use Domoticz as my controller.

[mfalkvidd]

Welcome to the MySensors community @mattiman !
Could you post the debug logs of the node and the gateway? That's usually the quickest way to get a hint on what is wrong.

If you haven't already, you can also look at https://forum.mysensors.org/topic/666/debug-faq-and-how-ask-for-help/ which has recommendations on the most common problems and how to troubleshoot them.

People have also been helped by this: http://blog.blackoise.de/2016/02/fixing-your-cheap-nrf24l01-palna-module/

[pepson]

Hi
I use Arduino Pro Mini 5V and i want user radio RFM69HW. I must use logic level converter from 5V to 3.3V to connect radio or i can only reduce power from 5V to 3.3V to VCC ?
On this page is nothing describe that i must use logic level converter,...but some users on this page write that i must use:
https://www.openhardware.io/view/268/RFM69HW-interstitial-board-for-Arduino-Pro-Mini#tabs-comments

Now i have connected only with reduce power to 3.3V but my Arduino not working still time. Only some minutes to test...

[gohan]

It was already answered to you in another topic and if you read in the openhardware project it is clearly stated that it is meant for pro mini 3.3v. If you connected it to a 5v pro mini you most likely fried the RFM69 module.

[pepson]

I connect to 5V Arduino but i use AMS1117 to step down power 5v to 3.3V and radio still working.

[manutremo]

I have two of my nodes using rfm69hw and mini pro 5v 17mhz. I only step down the power line to 3.3v, the comms lines work just fine with 5v. I also remember reading somewhere that this is actually the case, even though the datasheet says the opposite.

[gohan]

I'd follow the datasheet and don't take the risk of frying the radio.

[manutremo]

They've been working for more than 6 months now as part of a test run and are not yet fried.

There is other people around reporting the same with at least the rfm69HW. I remember someone stating that the new models are more robust in this regard than older models, in spite of the manufacturer not yet stating 5v tolerance in the data pins.

In fact the datasheet never mentions 5v intolerance, and it does never actually mention a max voltage for the data pins, only for Vdd.

It seems like the board does something with the voltages in the data pins anyways, since if it was using the definitions of the logic levels (as a percent of Vdd) as they appear in the datasheet, it should not be able to communicate at all with a 5v arduino when powered at 3.3v and no logic level shifter on the data pins - but it does.

This doesn't mean this is good practice, directions in the datasheet are there for some reason and my nodes will eventually get a logic level shifter when they finally go into their final case. But reality is it seems at least RFM69HW can tolerate 5v for months without being fried.

[gohan]

still I would not advise someone to go ahead and use them without a level shifter as I would not take responsibility to damage someone else hardware 3.3V is still able to talk to 5V, depends on how large is the tolerance zone around the 2.5V grey zone of the arduino