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Radio Link

I'm looking at possible ways to design a radio link system.

The basic idea is for a lasertag environment. Each pack will carry a radio tranceiver, and there will be communication points around the arena.

I've looked at a few options, but i'm not sure what the best option would be. I've seen the EasyRadio products which look good, they provided a serial interface and seem suited to the application. I've not done any testing, but it worries me that they sit on the same frequency all the time - a perfect candidate for something giving off interference on that frequency and killing the system.

I then looked at WiFi which offers spread-spectrum transmission. This looks good but its complex to implement and appears to consume more power. I'm also concerned that the frequency can be heavily used and as a result quality of service could suffer. This has the plus that cheap common WiFi access points can be used and linked to an ethernet hub to allow for all the communication.

The main things I'm looking for are, cheap to implement, very reliable (can't afford to have a centre with packs dropping on/off line), low power usage (its a mobile app.). Its also a development time thing, I can't afford to spend months writing TCP/IP layers etc! Any suggestions?

Thanks in advance.

Mike

Reply to
mjt
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Given your criteria (particularly the need to have little development time and low cost) I suggest assigning one frequency for base station Tx and one frequency for each pack's Tx. This might mean having 50 packs, of course.

You could test this system (illegally) by putting a simple data slicer onto a GPRS radio, which can be be bought for about $15 a pair.

Reply to
zwsdotcom

Don't design - buy. :-)

This looks like a perfect niche for RC-type equipment, like they fly those model airplanes with. I did a quick google search:

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and this was the second hit:

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So you can get some idea of just how many independent transmitter/receiver pairs you could support.

Have Fun! Rich

Reply to
Rich Grise

If all he needs is a hit recorder, he could put a simple little crystal oscillator on each player with either a wideband receiver that can distinguish which channel is transmitting, or a bank of receivers, one per channel, which wouldn't be very hard to do either, if you're inside a laser tag arena. Kinda tedious, however. :-)

I was kinda surprised that there are 45 channels in the "72 MHz" band (I don't know its official name) which apparently either doesn't need a license, or the stuff is already licensed:

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Cheers! Rich

Reply to
Rich Grise

Thanks for the ideas.... just to clarify - I'm not planning on building the core RF, data slicer, or even the manchester coding section if I can help it!

I guess the key question is - in the event that I design it to operate off a single frequency, whats the likelyhood that RF intereference could knock it out? Would spread-spectrum be the best way to go, and if so is there an off-the-shelf solution? As mentioned I've seen EasyRadio which looks good, but is limited to a single frequency.

The idea of a channel per pack isn't practical - the maximum will probably be 60 packs per game, with the possibility of a large centre having two arenas next to each other. The packs also need to receive settings for the game, when to start the game etc. plus you need to know who has hit who.

Mike

Reply to
mjt

It's only a day's work to design everything downstream of the RSSI output. For someone who knows much more about RF than I do, it's probably a day's work to design everything.

It's possible but unlikely. Design your receiver with good selectivity.

You don't want to design this.

That doesn't preclude using a separate downstream channel for each pack. You could have a master device in the ceiling of the arena.

Reply to
zwsdotcom

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