(cheap), Long range module (node to node) RFM95?

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(cheap), Long range module (node to node) RFM95?

Postby MJU » Sun Dec 23, 2018 1:07 am

After testing several wireless devices (433Mhz, wifi and so), I really feel the need for a simple, node to node device.

I found out that via LORA, sending messages between two nodes is possible. (did I hear right?)
What I always hear is that LORA is much more sensitive and has a far better transmit range then other TX/RX techniques (true?).

So why not try this technique to send simple messages between two controllers in an environment that has some obstacles?

Does anyone have experience with this techniques?
Is the RFM95 a good solution to send and receive short messages (no high bitrates) from my house (brick walls), to another building with brick walls let's say 50 meters from each other?
After ordering many modules that promise "long range", I could not get this done.

If the RFM95 could be used for this, why not make a component for this?
Or another (cheap) device that could accomplish this task?

So: a component that could switch between RT/TX would be welcome.
Thanks

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Re: (cheap), Long range module (node to node) RFM95?

Postby viktor_au » Sun Dec 23, 2018 4:50 am

Hello MJU

I think johnsondav made a component for 433 MHz module, but I am not sure if he has moved to explore the Lora field.
I would like to make the RF beacon myself, however I am not sure about the synchronisation between the Tx module message and the Rx module message.
Can you share the 433 MHz projects?
Do you use UART? What baudrate?

I found on net the next:
It is not a good idea to use UART to transmit data wirelessly.
Wireless is VERY sensitive to noise and has a lot of other problems. Usual way is to transmit preamble (used by RF receiver to adjust gain, etc) and than data in some error correcting way. You could send using Manchester coding or send 1's as 1mS and 0'2 as 3 mS pulses.

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Re: (cheap), Long range module (node to node) RFM95?

Postby mnf » Sun Dec 23, 2018 9:58 am

There are several alternatives:

The NRF24L01 is reasonably well supported in FC - and the versions with external antenna and a booster have reasonable range.
https://www.banggood.com/1100-Meter-Lon ... rehouse=CN

I have some Dragono Lora shields that I have working from C++ - and at some point hope to try in FC which 'promise' a 4km to 10km range - but I suspect that this would be line of sight and obstacles (houses etc) will drastically impair this..
See http://www.dragino.com/products/lora/it ... hield.html - I believe that Dragino produce a weatherproof receiver station - and an outdoor receiver may help (depending on the wall thickness and construction?)

Could you use a couple of ethernet shields and 'ethernet over mains' adapters?

Martin
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Re: (cheap), Long range module (node to node) RFM95?

Postby kersing » Sun Dec 23, 2018 1:02 pm

RFM95 in LoRa mode (it can do fsk as well) should be able to get you at least 50m with multiple obstacles in between. If you want to try before a component is available, you could check the code available in the Arduino community.

Keep in mind LoRa uses minimal transmission energy to stay within the legal limits. In urban environments its range will be a fraction of the 15km listed sometimes. Out in the open with line of sight it can be hundreds of kilometers. Typical range in an urban environment will be between 50m and 1km.

No need to go the Dragino ‘station’ route, the modules can communicate directly (when using LoRa, not for LoRaWAN which I suspect the station uses).
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Re: (cheap), Long range module (node to node) RFM95?

Postby MJU » Sun Dec 23, 2018 11:46 pm

mnf wrote:There are several alternatives:

The NRF24L01 is reasonably well supported in FC - and the versions with external antenna and a booster have reasonable range.
https://www.banggood.com/1100-Meter-Lon ... rehouse=CN

I have some Dragono Lora shields that I have working from C++ - and at some point hope to try in FC which 'promise' a 4km to 10km range - but I suspect that this would be line of sight and obstacles (houses etc) will drastically impair this..
See http://www.dragino.com/products/lora/it ... hield.html - I believe that Dragino produce a weatherproof receiver station - and an outdoor receiver may help (depending on the wall thickness and construction?)

Could you use a couple of ethernet shields and 'ethernet over mains' adapters?

Martin


Thank you.
The Flowcode component for the NRF24L01 is based on work I did (can tell because of some things that are still inside).
But the range is poor for what I want to accomplish.
1 wall and the signal is reduced enormously.

I never believe the figures that are given with the devices. Tests on the internet always show figures in open air, line of sight.

I really want to test the LORA-shields, but node to node (not via a gateway) and hope Flowcode will help me :-)

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Re: (cheap), Long range module (node to node) RFM95?

Postby MJU » Sun Dec 23, 2018 11:54 pm

kersing wrote:RFM95 in LoRa mode (it can do fsk as well) should be able to get you at least 50m with multiple obstacles in between. If you want to try before a component is available, you could check the code available in the Arduino community.

Keep in mind LoRa uses minimal transmission energy to stay within the legal limits. In urban environments its range will be a fraction of the 15km listed sometimes. Out in the open with line of sight it can be hundreds of kilometers. Typical range in an urban environment will be between 50m and 1km.

No need to go the Dragino ‘station’ route, the modules can communicate directly (when using LoRa, not for LoRaWAN which I suspect the station uses).


Thank you, but I really want to have a Flowcode component too :-)
That's the reason I have Flowcode, not to have to use the Arduino community.

But I will give it a try. Do you have, by any chance, an (Arduino) example that I can use to test this (send and receive bytes, node to node)?

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Re: (cheap), Long range module (node to node) RFM95?

Postby viktor_au » Mon Dec 24, 2018 3:03 am

Any chance you can share some of your 433 MHz projects please?

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Re: (cheap), Long range module (node to node) RFM95?

Postby MJU » Wed Dec 26, 2018 6:13 pm

viktor_au wrote:Any chance you can share some of your 433 MHz projects please?


Sure, but these files were made with Flowcode 5..
I have Eblocks (I think EB063-433) with 433Mhz transmitters and made them for this purpose.

I never used the generic 433Mhz modules to test the range.

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Re: (cheap), Long range module (node to node) RFM95?

Postby chipfryer27 » Fri Dec 28, 2018 11:57 am

Hi

I don't know the budget but you may consider products from RF Solutions (https://www.rfsolutions.co.uk/radio-mod ... lated-p427). I have been using their Gamma modules for years. Many options available from simple input / output to full modem. Depending on antenna and obviously conditions you can get many, many miles.

Easily interfaced with any uC or can be a simple "stand alone" transceiver or Tx / Rx unit.

I have used them "paired" with a uC providing an interface between sensor and RF module and also as a modem. The Flowcode RS232 component made it very easy to interface.

Hope this helps.
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Re: (cheap), Long range module (node to node) RFM95?

Postby kersing » Fri Dec 28, 2018 3:03 pm

On the Adafruit site there is example code for RFM95 node to node communication. Make sure to use a frequency legal for your location and matching your module. In Europe I would avoid the lorawan frequencies 868.1/.3/.5 MHz as there will be a lot of ‘noise’ generated by other users (there will be other frequencies used for lorawan as well but these will be the busiest ones)
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Re: (cheap), Long range module (node to node) RFM95?

Postby MJU » Fri Dec 28, 2018 4:47 pm

chipfryer27 wrote:Hi

I don't know the budget but you may consider products from RF Solutions (https://www.rfsolutions.co.uk/radio-mod ... lated-p427). I have been using their Gamma modules for years. Many options available from simple input / output to full modem. Depending on antenna and obviously conditions you can get many, many miles.

Easily interfaced with any uC or can be a simple "stand alone" transceiver or Tx / Rx unit.

I have used them "paired" with a uC providing an interface between sensor and RF module and also as a modem. The Flowcode RS232 component made it very easy to interface.

Hope this helps.


At first sight this looks great!
RS232 data to control the device... hmm great.

Maybe I will contact you for further information, I will first have a look into the datasheet.
Thanks

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Re: (cheap), Long range module (node to node) RFM95?

Postby MJU » Fri Dec 28, 2018 4:49 pm

kersing wrote:On the Adafruit site there is example code for RFM95 node to node communication. Make sure to use a frequency legal for your location and matching your module. In Europe I would avoid the lorawan frequencies 868.1/.3/.5 MHz as there will be a lot of ‘noise’ generated by other users (there will be other frequencies used for lorawan as well but these will be the busiest ones)


Thanks for the advice.
Wouldn't it be great of Flowcode had such a component? :-)

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Re: (cheap), Long range module (node to node) RFM95?

Postby chipfryer27 » Sat Dec 29, 2018 12:40 pm

Hi MJU

The units are incredibly easy to interface. Depending on how you configure them (pins held high/low/NC) they even provide internal pull-ups so all you need to do is drag an input low. If "paired" in Tx/Rx mode then you can have eight individual inputs that when "triggered" will send status to the receiver which will then reflect the status on its output. If connected to a uC it is a piece of cake using Flowcode to either set the pins high/low and also to read them. I usually assign all pins of a port to the unit if I'm using it this way.

Setting addresses and other configurations such as power etc for the modules is easily done with a terminal program. Using them as a modem for bidirectional comms is straightforward as long as you are only sending small packets. The RS232 component and Circular Buffer come into their own.

At the risk of sounding like a salesman for these units (I'm not) I used three modules in a site out in Wales to monitor water tanks. Two were used as Tx units paired with the third unit configured as a receiver. The Tx units only had the module, 2xAA batteries and a float-switch. When water level drops to a certain level the units transmit status to the receiver.

The receiver is located inside of an old stone cottage. WiFi is useless within. The lower tank is about 100m down a hill and has no LOS of the cottage. The upper tank is only about 40m away and has LOS but on the opposite side of the house from the receiver. All units communicate with ease. The receiver connects to a PIC using a couple of pins and there are associated LEDs / buzzer to signal alerts. I also used an ESP866 module to connect to the internet (router is in same room) so that alerts are sent out by email etc upon activity. All programming done with Flowcode and if I remember correctly Kersing kindly provided an updated ESP component for use.

Hi Kersing

I don't claim to be an RF expert which is why I like using modules :) You may find this of interest. I have a RF signal strength meter supplied by RF Solutions that is "tuned" to their LoRa frequencies. Yesterday I undertook some tests just to gauge range prior to a deployment (although not in this actual area). At present I'm in Chelsea slightly east of Worlds End and I put a Tx unit on the roof set to pulse out a signal at 868Mhz. I am beside the river. I walked up and eastwards along the Kings Road looking at the signal strength meter as I went. The meter goes down to -110db. Occasionally I would see background noise around the -110db mark. This did become more noticeable around the fire-station when it would peak at around -100db. I could still make out my "pulse" but only just on the meter.

I crossed the river and went into Battersea park. I didn't see much of any background noise there (unsurprisingly) but my pulses were very clear peaking around -78db at the south east point of the park.

For those unfamiliar with the area, the fire station is about a mile as the crow flies from my Tx unit and there is no direct line of site, instead many buildings. The park is, well a park but I still do not have direct LOS as there are still a few buildings in the way, but distance was I'm guessing still over a mile.

Regards

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Re: (cheap), Long range module (node to node) RFM95?

Postby kersing » Sat Dec 29, 2018 2:04 pm

distance was I'm guessing still over a mile.


I’ve been working with LoRaWAN (based on LoRa) for over three years now and one thing I can guarantee is that predicting radio coverage is impossible. I’ve seen it working inside older buildings with multiple 2 feet reinforced concrete floors between receiver and transmitter and I’ve seen it fail with just a few new builds between them.

The difficulty is radio signal propagation is not straight forward. Signals will be reflected, diffused and ‘bent’ around corners.
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Re: (cheap), Long range module (node to node) RFM95?

Postby chipfryer27 » Sat Dec 29, 2018 2:33 pm

Hi Kersing

That's why I "hate" RF...:)

I'm pretty certain I will meet my expected distance of about two miles over relatively open ground though.

Regards

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Re: (cheap), Long range module (node to node) RFM95?

Postby Jay Dee » Fri Mar 08, 2019 7:18 pm

Hi,
Bit late on this one... but I've also used various versions of the the RF Solutions LoRa tranciever modules (Gamma). Through trees and varying countryside terrain I achieved a very reliable 1Km connection. Beat any other small low power RF tansmitter I've tested by a long way.
In its simpliest form, its 8 channels one way or can be set for 2x4, giving a crude two way. This only required interfacing digital I/O pins.

But if you interface with the on-board Serial .... I've been sending my own message packets with 12bytes of data once every few seconds. Its been great.

I'm hoping to look at the smaller and cheaper 'LoRa Transiever only' (Lambda) module but then I have to deal with all the details and interface with the chip directly so lots more reading of the semtech datasheet and this is not supported by RF solutions much, they just supply the hardware.
With both versions, it is certified so you can actually deploy it in a product without having to re-certify the RF side! . J.