[TriEmbed] Long range digital communication (long range wifi, XBee?)

Carl Nobile carl.nobile at gmail.com
Thu Oct 25 16:20:47 CDT 2018


Not sure if this would be something you'd be interested in. They have some
LORA boards on a Kickstarter

https://www.kickstarter.com/projects/pisupply/iot-lora-boards-your-gateway-to-the-internet-of-th

~Carl

On Thu, Oct 25, 2018 at 5:18 PM Tadd Torborg via TriEmbed <
triembed at triembed.org> wrote:

> Hmm.. I pasted this to the wrong stream I think.  Sorry if this is a
> duplication
>
> I would suggest using a 900Mhz base station someplace on the property
> where there is an RF view to the rest of the property.  You are allowed 1
> watt with a frequency hopping system.  Then use stations in the robots and
> wherever your control system is, all within almost line-of-site with your
> base station.  You can get 100kbits/sec shared bandwidth.  you’d have your
> base station set up as a channel control device offering up time-slots to
> your mobile assets and the control station.  If you had 2 robots you’d
> probably end up with 2000 or 3000 bytes per second per robot, split between
> robot transmissions and robot receptions.
> Part 15.247 FCC rules I think.
>
> no cost for operation.
>
> This isn’t going to work for full motion video but snapshots should be
> possible and you can do reasonably high speed navigation with GPS, sonar
> ranges and Remote Control motor management in real time with this kind of
> system.
>
> Vendors:
> Search the web for 900mhz spread spectrum radio”    You’re looking for
> 15.247 I think if you need to narrow the search.
>
> This can be in-house manufactured too depending on your volume.  There are
> plenty of single chip 900 radios.  Many of the LoRa radios can be used in
> FSK mode for this but you’ll need a PA to get the range you need I think.
> In the short run you can do in-house testing with bare modules based on the
> SemTech 900 radio-on-a-chip if you want to go it from scratch.
>
> FHSS rules are that you can stay on one frequency for up to 400mS, you
> generate your own transmit sequence and apply it in every device.  You have
> to hop through 25 or more frequencies.  You can repeat every 20 seconds.
> The base station would send some synchronization info every time it ends up
> on your hop sequence channel 0 or something like that.  Any device which
> has lost the FHSS sequence index would camp out on channel 0 until it hears
> the base station send out the synchronization info.
>
>      Tadd
>
>
> Tadd / KA2DEW
> tadd at mac.com
> Raleigh NC  FM05pv
>
> *“Packet networking over ham radio": **http://tarpn.net/t/packet_radio_networking.html
> <http://tarpn.net/t/packet_radio_networking.html>*
> *Local Raleigh ham radio info: **http://torborg.com/a
> <http://torborg.com/a>  *
>
> On Oct 25, 2018, at 3:23 PM, Charles West via TriEmbed <
> triembed at triembed.org> wrote:
>
> Hello!
>
> I'm in Lansdale, PA now but I was hoping I might be able to pick you guy's
> brains.  My current big project is trying to build one or more robots to
> deliver food/drinks on golf courses.  I'm currently trying to figure out
> the best way to maintain continuous(ish) contact between a access
> point/basestation at it's base of operations and 1 or more robots operating
> on the course.
>
> At a minimum, I would like to have the robot report its basic status
> (battery percent, GPS position) but it would also be great if it could
> stream video when required to allow teleprescence steering or determination
> of what is going on.  The robot would probably be about 1 km from the base
> station at max.
>
> I'm currently considering 3 possible solutions but I'm pretty open to
> ideas:
>
> 1.  Use a mobile hotspot/cell modem:
>         For fixed $130 and monthly $20, I can get a mobile hotspot which
> provides one gig of data per month and more data for $5/gig.  If I keep the
> reporting really light, this could work but the communication would have to
> be kept pretty limited.
>
> 2.  XBee:
>          These modules seem to float somewhere between $25 and $60 in
> prices, so a pair would be somewhere in the $50 to $120 range.  Sparkfun
> had a good guide to XBee (https://www.sparkfun.com/pages/xbee_guide) but
> they are listing almost all of their products as retired (besides old
> series 1) and most of the stuff I read about XBee is from 2015-2016 so I am
> not sure what the best options are anymore.  In any case, it looks like it
> would provide a low baud rate connection over the desired range.  The main
> problem is that it requires working through XBee and making my basestation
> have to have special software to forward information.  I'm also not sure
> about security and it is certainly not going to be streaming video.
>
> 3.  Long range Wifi:
>         Rodney's done some work in this area before with his weather
> balloon projects.  I don't recall off the top of my head how far he managed
> to get but I do remember he had to use higher power than allowed without a
> higher grade amateur radio license.  That power level would not work for a
> commercial operation.  There are some companies that are selling solutions
> aimed at farms (http://ayrstone.com/www/?v=7516fd43adaa) and there seem
> to be off the shelf solutions that can get 500 ft (mostly aimed at
> hotels).  The hotel systems seem to be in the $350 range and the farm
> systems in the $500 or so.  The robot could use a high gain antenna, but it
> is not clear how much it helps.  These systems have security built in and
> potentially can stream video if the range is long enough.  Like hotspots,
> writing software for them would also be easy.
>
> What do you guys think?
>
> Thanks,
> Charlie
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Carl J. Nobile (Software Engineer)
carl.nobile at gmail.com
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