Re: gEDA-user: OT: Bike Alarms

[David SMITH <dave.smith@xxxxxx>]

David C. Kerber wrote:
> Remember what the original suggestion was:  have the device wake 
> up for a few seconds once a day and send a message as to where it
> is (or maybe only send that message if it's not where it's supposed
> to be).

Yes, I remember the original suggestion; I don't know what the GPS
performance is, but most GPSs have a cold-start TTFF of a few minutes,
so the "few seconds" is already "a few minutes".  I'm  not necessarily
saying that the problems are necessarily insurmountable, just that I
think that there might be a bit more of a problem with power consumption
than you think.

Of course, we also have the problem of getting a decent  GPS fix, since
if it's stolen, it will need to get enough signal to report its
position, and if it's being stored inside a building, that's going to be
very difficult, even before you take the possibility of a metal-framed
bike into account.

> Considering that a typical bike-mounted gps (Garmin Edge 305, for 
> example) can run for several hours on 3xAA batteries, including gps,
> cadence, heartrate and speed sensors, along with a continuous display, 
> I think a couple of AA batteries would power this thing for several 
> months or even years, at a few seconds per day.

I doubt that the cadence/heartrate/speed measurement is going to have
any significant effect on the power consumption - most non-GPS cycle
computers will do that for months if not years on a coin cell.  It's the
GPS and GSM that suck the power.

> And if you can tie it in to Shimano's DI-2 power pack, it will have 
> its power routinely recharged by the user every few weeks for other
> purposes any way.

True, but then it becomes more difficult to hide inside the frame, and
get wires into/out of the frame.


_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user