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OA47
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Posted: 04 September 2017 at 2:00am | IP Logged Quote OA47

I am about to order some LORA modules from that well known auction site and was wondering if there were any comments or recommendations from shedders. I wish to monitor some sensors via Micromites (up to 20 units) that will be located in the field up to 3 KM from the nearest internet connected PC which is approx. 100KM from my SHED. My requirements would be to have a low standby current as they will need to be solar powered and an RS232 port as I would anticipate that the data could be transmitted via the console port to the receiving unit and also give remote access to modify the program on the Micromite whilst it is in its initial operation.

Here is a link to some units that have my attention:
433Mhz LORA modules

I would appreciate any comments from the learned shedders.
Graeme


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Grogster
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Posted: 04 September 2017 at 7:01am | IP Logged Quote Grogster

I have not used those ones, but any reason you are not considering a couple of HC12's?

They also have 100mW output, multiple channels etc, and are only about $5 each.
Even cheaper then that if you buy ten or more in one go.

Be aware that you'd be hard-pressed to get 3km out of 100mW - even line of sight.
I suppose if you had lots of height(IE: No obstructions), and directional antennas with some gain.....

I would be looking for more juice then 100mW if you need 3kM.
Radio regulations would also come into play when you need to transmit that kind of power to get that kind of range.

Can you please confirm that your 3km and 100km statements are correct and not typos.

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OA47
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Posted: 04 September 2017 at 7:13am | IP Logged Quote OA47

Thanks for the reply Grogs. I sorry if my post was a bit ambiguous. I am aware of the HC-12 units but the radio range needs to be a reliable 3 km that is why I have been studying the Long-Range (LORA) variety of the modules. I believe that the spread spectrum mode of these devices gives them the ability. It is the controlling and data gathering PC that is 100Km away and the one that I would connect to via the inet.


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lew247
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Posted: 04 September 2017 at 7:16am | IP Logged Quote lew247

Hc-12's are only very short range and the data transfer is very fast
The Lora modules are specialist units that do work up to several Km's away - brilliant for long range but slow data transfer so can't be used for things that need fast data transfer
3Km with those modules is no problem even with the very low power output

a review on them here

and an indestructable articlehere

Edited by lew247 on 04 September 2017 at 7:20am
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OA47
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Posted: 04 September 2017 at 7:22am | IP Logged Quote OA47

Lew247, I am afraid that the first hyperlink you posted has been hijacked.
https://www.facebook.com/uniladmag/videos/2283040031719043/

EDIT:
2nd One looks OK

Edited by OA47 on 04 September 2017 at 7:23am
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lew247
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Posted: 04 September 2017 at 7:43am | IP Logged Quote lew247

OA47 wrote:
Lew247, I am afraid that the first hyperlink you posted has been hijacked.
https://www.facebook.com/uniladmag/videos/2283040031719043/


ARGHH... no idea how that happened sorry. I can't edit it now either. never saw that happening before, because it was a copy and past of a review I was reading - it was nothing to do with facebook at all

The link was actually this page http://vanderleevineyard.com/vineyard-blog/long-range-wireless-networking-module-review

Edited by lew247 on 04 September 2017 at 7:45am
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Grogster
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Posted: 04 September 2017 at 8:46am | IP Logged Quote Grogster

I stand corrected.

Might have to get a couple of those to play with myself now.

Clickable 1st link...



Edited by Grogster on 04 September 2017 at 8:47am


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srnet
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Posted: 04 September 2017 at 8:43pm | IP Logged Quote srnet

[QUOTE=OA47]Here is a link to some units that have my attention:
433Mhz LORA modules
/QUOTE]

Those are UART front ended LoRa modules, so they may not have a sleep mode.

A native SX127x LoRa device is addressed via an SPI interface. These modules are easy to put to sleep and consume only a few uA. Not difficult to drive either.

For your application LoRa is the way to go, nothing else will come even close to the range. Its not possible to be specific, as environements vary so much but 3km would be trivial for LoRa, you may only need 2dBm\1.6mW for sensor reading applications. The LoRa modules (RFM9x, DRF127x) are capable of 50mW, but your not going to need that sort of excessive power unless the 3km is through dense and wet forest.

I did publish some Micromite code for the LoRa SPI devices a couple of years ago, not a lot of interest in it really.

Lots of stuff on the capability of LoRa here;

https://github.com/LoRaTracker/Test-Reports

The report "Semtech LoRa Transceivers a KISS approach to Long Range Data Telemetry - January 2015" compares a typical FSK style tranceiver (RFM22B) with a LoRa device.



Edited by srnet on 04 September 2017 at 8:46pm


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Posted: 05 September 2017 at 12:47am | IP Logged Quote Grogster

srnet wrote:
For your application LoRa is the way to go, nothing else will come even close to the range. Its not possible to be specific, as environements vary so much but 3km would be trivial for LoRa, you may only need 2dBm\1.6mW for sensor reading applications.


Now I want to know HOW they can get that kind of range, out of that kind of power, on that kind of frequency.

Can anyone link me to anything technical on LoRa so I can have a read?

Edited by Grogster on 05 September 2017 at 12:47am


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Posted: 05 September 2017 at 3:37am | IP Logged Quote yahoo2

Grogster wrote:

Can anyone link me to anything technical on LoRa so I can have a read?


its basically designed around super low bandwidth and gateways.

You might be better off watching one of Andreas Spiess's videos to get a feel for the big picture first.

#112 LoRa / LoRaWAN De-Mystified / Tutorial

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srnet
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Posted: 05 September 2017 at 6:10am | IP Logged Quote srnet

Grogster wrote:
srnet wrote:
For your application LoRa is the way to go, nothing else will come even close to the range. Its not possible to be specific, as environements vary so much but 3km would be trivial for LoRa, you may only need 2dBm\1.6mW for sensor reading applications.


Now I want to know HOW they can get that kind of range, out of that kind of power, on that kind of frequency.

Can anyone link me to anything technical on LoRa so I can have a read?


Why does LoRa cover such long distances?

First of all, understand that quoted data sheet sensitivity for an RF device is as a result of perfect World tests in a laboratory. Unfortunately our RF devices have to work in the real World where there is a lot of RF noise about.

A typical FSK receiver, RFM22B, HC12 etc. will have a data sheet quoted sensitivity of -121dBm or so. With the receiver seeing a typical real world noise level of -100dBm to -105dBm, that would seem to imply that our typical FSK receiver is capable of receiving signals at -121dBm or up to 20dBm below noise level. Thats just not going to happen. Typical FSK devices actually need a positive SNR of between +5dB and +10dB for the receivers to work. In other words these FSK receivers actually need signals of around -90dBm to -95dBm to work, and not the data sheet claim of -121dBm.

The real limiting factor on reception at UHF is the relationship between the signal and the noise level seen by the receiver, i.e. the SNR.

The trick that LoRa pulls is that by using spread spectrum techniques it is capable of receiving signals that are below noise level. Typically -10dBm at 1500bps and -20dBm at 100bps.

So whilst a typical FSK receiver needs a positive SNR of +5dB or more to operate, a LoRa device can work at between -10dB and -20dB, which represents a link budget improvement of between 15dB and 25dB.

A 25dB link budget improvement represents a distance gain of 18 times or so.



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srnet
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Posted: 05 September 2017 at 6:27am | IP Logged Quote srnet

yahoo2 wrote:
Grogster wrote:

Can anyone link me to anything technical on LoRa so I can have a read?


its basically designed around super low bandwidth and gateways.

You might be better off watching one of Andreas Spiess's videos to get a feel for the big picture first.

#112 LoRa / LoRaWAN De-Mystified / Tutorial


A quite missleading video, taken out of context.

LoRa is a receiver protocol invented by Semtech, its a protocol in the same way that RFM22Bs and HC12s use FSK as a protocol. LoRa can be used point to point in the same way as RFM22Bs, HC12s and nRF24L01 can be. LoRa does not need a 'gateway'.

When compared with our normal FSK UHF devices, RFM22B, HC12, CC1101 etc, LoRa is in fact very wide bandwidth. An FSK device might use a bandwidth (deviation) of 5Khz or so whilst a LoRa device will typically use 40KHz or higher. I use a LoRa bandwidth of 62Khz for my trackers.

LoRaWAN is a wide area networking system that uses LoRa as its base communication technology. Typical bandwidth is 125Khz, but 250Khz or 500KHz can be used.

LoRaWAN is a

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