Instead of Lora, what? - Page 1
Forum section: electronics / projects

author: panoss
author_rank: Frequent Contributor
timestamp: April 18, 2019, 11:15:32 am
content: I 've made a Lora (RA-01) temperature meter.I want to put the transmitter on the top of a 7 floor building.The receiver on the ground.This means the signal will have to be able to pass through 7 floors.I haven't tested it yet if it can do this, but I was thinking ofalternatives in case it fails.For example, I have a wireless door bell which works in a long distance and through many walls.I guess it has a quite strong transmitter.So how could I use a transmitter and a receiver from a door bell with an arduino?

author: JVR
author_rank: Regular Contributor
timestamp: April 18, 2019, 01:15:27 pm
content: Dont plan to fail. LoRa should do it easy enough if the RF design was done properly. If not, there are always PA's available.

author: panoss
author_rank: Frequent Contributor
timestamp: April 18, 2019, 02:00:21 pm
content: Quote from: JVR on April 18, 2019, 01:15:27 pmWhat RF design? I just connected the Lora module with the Arduino, what RF design are you talking about?Quote from: JVR on April 18, 2019, 01:15:27 pmWhat are PA's?

author: JimRemington
author_rank: Regular Contributor
timestamp: April 18, 2019, 04:05:37 pm
content: PA = power amplifier.Be sure to use antennas on the RF modules.

author: ogden
author_rank: Super Contributor
timestamp: April 18, 2019, 04:41:25 pm
content: Quote from: panoss on April 18, 2019, 11:15:32 amSigfox then. Yet, it is not much better than LoRa, IMHO. Anyway 7-floor building does not mean that radio waves have to pass through 7 floors in straight line. They have ability to reflect/bounce. Most likely LoRa will be fine in any building having any number of floors unless that building stands alone in the middle of the nowhere. If you need hi-reliability system - make space-division MIMO (at least two base stations located in different locations).

author: panoss
author_rank: Frequent Contributor
timestamp: April 18, 2019, 04:44:44 pm
content: Quote from: JimRemington on April 18, 2019, 04:05:37 pmYes I'm using the ones that came with the modules:So, in case I need it (I suppose I won't, but just in case), where can I find a PA for Lora?(you mean somethinglike this?)

author: ebastler
author_rank: Super Contributor
timestamp: April 18, 2019, 04:55:57 pm
content: Can't you go "around" the building instead of through all seven floors? I.e. place the transmitter on the side of the building, or on the roof but as close as possible to the edge. Place the transmitter outside a window on the ground, or maybe just inside behind the glass. I would expect a significantly stronger signal that way than if you have to go through seven iron/concrete floors.

author: panoss
author_rank: Frequent Contributor
timestamp: April 18, 2019, 05:00:10 pm
content: I thought of this, but it would not be a very...'elegant' solution (for the client).

author: ogden
author_rank: Super Contributor
timestamp: April 18, 2019, 05:02:09 pm
content: Quote from: panoss on April 18, 2019, 05:00:10 pmInstead of asking public forum where anybody can tell you virtually anything, do site survey instead.

author: ElectronicCat
author_rank: Regular Contributor
timestamp: April 18, 2019, 05:51:44 pm
content: LoRa has one of the highest link budgets of any readily available consumer kit, it that doesn't work I'd be very surprised and you're pretty much out of luck. As I think others have already mentioned, the signal doesn't need to travel line-of-sight through the building, assuming there are other buildings and objects around there will be plenty of room for multipath propagation.If for some reason it doesn't work, the first thing I would try is replacing the fully loaded coil antenna with a full or half wavelength whip antenna or dipole rather than immediately putting in a power amplifier. If you add a PA you will almost certainly breach your local regulations on RF power emissions and the module you have probably already outputs more than enough power (100mW or so should be plenty).

author: hagster
author_rank: Frequent Contributor
timestamp: April 18, 2019, 05:54:19 pm
content: There are very few radio modules around with better link margin than LoRa. To get the best out of it you need to select the slowest data rate though.The spring antenna that come with your module is pretty crappy. You could choose a better one, or experiment with directional antennas. Remember the best RF link may actually be a reflected signal coming in through a window or something similar.An alternative is to use a different frequency. 433MHz for instance will be better at getting through the building structure.

author: Marco
author_rank: Super Contributor
timestamp: April 18, 2019, 06:40:08 pm
content: Main alternatives are CC1120 and SI4463, with the latter available on the dirt cheap RFM26W.169MHz looks like an interesting band, 500 mW ERP allowed. Used for Wireless M-bus, withslightly more expensive modules. Probably easier to use though.

author: panoss
author_rank: Frequent Contributor
timestamp: April 18, 2019, 07:12:06 pm
content: Quote from: hagster on April 18, 2019, 05:54:19 pmThe module I'm using works at 433MHz!From what you guys are saying, I expect it should work.I wil try it on Sunday and will let you know.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: April 19, 2019, 05:19:56 pm
content: I'm not a RF guy, but if both locations are fixed, then directional antenna's (cantenna) might help.Maybe it is even a good idea to purposefully bounce your signals of a nearby building instead of trying to penetrate 7 floors.

author: ogden
author_rank: Super Contributor
timestamp: April 19, 2019, 07:37:10 pm
content: Quote from: Doctorandus_P on April 19, 2019, 05:19:56 pmIn right circumstances directional antennas could help, for instance both antennas are aimed at window and uses nearby building as reflector. Yagi kind of antennas shall be considered. Cantenna at 433MHz would be more like 20" diameter 50" deep bucket, way too directional as well. Narrow beam antennas are good for long, direct line of sight links where both antennas "optically see" each other.

author: panoss
author_rank: Frequent Contributor
timestamp: April 21, 2019, 02:31:58 pm
content: Guys, you were right. It works!But what if I want a better antenna (in order to have a better signal, just in case) than the one that came with the modules?Do you have any suggestion?

author: ElectronicCat
author_rank: Regular Contributor
timestamp: April 21, 2019, 07:56:49 pm
content: Quote from: panoss on April 21, 2019, 02:31:58 pmYes...Quote from: ElectronicCat on April 18, 2019, 05:51:44 pmYou can either buy one pre-made for the wavelength you are using or make one yourself from an old clothes hanger (or any source of semi-rigid copper wire) cut to the correct length.

author: panoss
author_rank: Frequent Contributor
timestamp: April 22, 2019, 02:37:10 pm
content: Ok, a whip antenna is the simplest one as it's only a straight wire with a length of 34cm (half wavelength,according to what I read on the internet), I guess this is what I 'm going to make.Only thing that bothers me is it will have to get out of the box as it's dimensions are 13cm x 13cm.And find a metallic - elastic wire. (I suppose it 'd better be elastic)