<div dir="ltr"><div>I once read about the people that made VNC used a similar badging system to track people's movements within a building for transferring phone calls and such. They used a motion detector to allow the critter to not transmit all the time. I'm thinking that if you are sitting still, it'd beacon once or twice before entering sleep mode. It would wake up when you started walking... I'd hope that your stride would be enough vibration to wake it up. We'd just need a RC timer to keep it on for some number of seconds after movement was detected... like 2 minutes for example. A piezo element tied to a diode, cap and resistor would serve as a motion detector directly into a pin on the pic. The pic would actually program itself to sleep between transmissions for seconds at a time. Power averaged would be on the order of nanoamps, 10s of milliamps during the transmit cycle... 4800 baud transmitting 16 to 20 bytes is 200ms at say, 100mA. As far as battery life goes... if a tiny trak with a 300mw transmitter can last 100 hours on a 9v battery, that's pretty reasonable - that's 4 days at the EOC minimum.... more if you go off duty and don't move for a while. </div>
<div> </div>
<div>It would beacon randomly every 30 to 45 seconds while active. Maybe every 5 minutes when not active. Sorta like smart beaconing but since we can't tell direction, we just up the beacon rate when the wearer is wiggling the unit. It certainly shouldn't send an entire aprs packet... heck it doesn't know where it is, only it's callsign. So it could only beacon a callsign, perhaps an icon/symbol and a 3 bit message indicator (optional, but let's spec it from the start). I like the idea of a keyfob, and the idea of a name badge equally. Heck, even if this thing ended up being the size of a pager on your belt, that'd be OK. When you start to approach the size of a pack of cigs or a cell phone, people might start to not want to wear it... </div>
<div> </div>
<div>I'm thinking of using this even around our drills at the SCSG. What would be really kinda slick would be to actually put the badge to aprs converter on one of the official's golf carts. As he drives around, the badge to aprs coverter uses a GPS ot keep track of it's location to which it prepends the received badge IDs. And official driving past all our groups of troops would end up marking them on the map for us as a roving "proximity digipeater". We could use a few fixed installations such as on the commo trailer, mess tent and such... and one "rover" on the golf cart.</div>
<div> </div>
<div>Wes<br><br></div>
<div class="gmail_quote">On Sun, Jul 20, 2008 at 11:13 PM, Bob Bruninga <<a href="mailto:bruninga@usna.edu">bruninga@usna.edu</a>> wrote:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Regarding APRS RFID Name Tags:<br>
<div class="Ih2E3d"><br>>> Why not use those little 433mhz data transmitters?<br><br>> I hooked an early prototype SMT OpenTracker<br></div>> to one of those ... Frequency drifted a bit<br>
<div class="Ih2E3d">> with temperature extremes, but it was standard<br>> APRS decoded with a 70cm rig.<br><br></div>Great to hear of such testing...<br><br>That is the ideal approach, but I just figured the full APRS AX..25 was overkill and would take more power. THe winning application here is the one that is either complete passive (meaning it always works) or is a 1 year battery replacement (meaning it almost always works mostly)...<br>
<br>If it takes a battery per full day or weekend of operation, then I think it is a non-starter, since it simply will not be a 100% passive detector of the wearer's presence... everywhere and always...<br><br>I figured the DATA key-chain FSK transmitrers that have companion receivers and are immune to the effects of drift and all they have to send is a callsign/SSID (40 bits). Everything else is added by the RFID sensor.<br>
<br>Now I would like to know ideas on what additional bits might be needed?. Bout the only additional info I can imagine is an SSID or SYMBOL byte so that one ham can wear different name tags to convey slight differences...<br>
<br>CALLSIGN<br>SYMBOL (can be a very reduced subset)<br><br>But since almost everything that is germane to the event or situation is known and can be added by the RFID DOORWAY READER, I still have not come up with much other than callsign/ssid is all that is needed. Ideas?<br>
<br>in fact, SSID is not really needed since again, the doorway-reader can flag it as a RFID and not any other use under that persons call...<br><br>And that makes it work perfectly under the KISS principle!<br><br>Bob, WB4APR<br>
<div>
<div></div>
<div class="Wj3C7c"><br><br><br>_______________________________________________<br>aprssig mailing list<br><a href="mailto:aprssig@lists.tapr.org">aprssig@lists.tapr.org</a><br><a href="https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig" target="_blank">https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig</a><br>
</div></div></blockquote></div><br><br clear="all"><br>-- <br>Wes<br>---<br>Where there's silence, there is no Hope. </div>