Keeping 'order' without RTC.

Just get a Sure reciever-- about $35 US, with an antenna (mind you their antenna is pretty cheap and one of mine failed) It will give a pulse per second (PPS output) plus a usb NMEA output so you can make your RPi's time accurate to 100s of nanoseconds (Just the NMEA itself is good to tens of ms, but since we are comparing to using a recorded time that is still about 1000 to 10000 times better.)

The Sure requires 5V, delivers TTL but most serial ports will be OK with that although the RPI probably wants less than that on its GPIO pins. (stick a diode or two in series with the PPS signal should bring it low enough)

The board is about the same size as the RPi. One problem might be the power draw by the RPi if he really is running his system off a battery. It would probably double the power requirement.

But there are others-- eg

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Not sure what a "blind" gps is, but they tend to be more expensive.

Reply to
William Unruh
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For a Raspberry a USB GPS would probably be cheaper and simpler - bearing in mind the GPS will probably have to be mounted in the roof (depending on whether the roof is insulated in foil faced insulation) or near a window on the end of a long cable (USB lengths permitting).

Reply to
Tim Watts

They should keep with the times and fire a Li-Ion Battery daily :-)

Reply to
Rob

Silly!

No receiver at all is required, just get a module like described in here:

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It will cost much less, will not be dependent on an antenna, and it is more than good enough for this application.

Reply to
Rob

If Mr Glur keeps his manners, GPS is not a solution: The GPS system does not take the leap seconds into account, so it is now about 15 s off UTC.

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-TV
Reply to
Tauno Voipio

On 04/03/2015 08:43, Tauno Voipio wrote: []

Most, if not all, deliver UTC and not GPS time directly.

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Cheers, 
David 
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Reply to
David Taylor

Wow!! How do *I* [want to] know the time?! We use computers to automate! I switch the battery-powered rPi on & off in the darkness, through a mosquito-net.

Reply to
Unknown

Thats another reason for using a 'blind' GPS rather than a handheld: many of them are sealed, weatherproof units.

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martin@   | Martin Gregorie 
gregorie. | Essex, UK 
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Reply to
Martin Gregorie

And damn expensive (several hundred pounds).

I think a blind GPS with RS232 downlink (or RS485 with 232 converter as in the Trimble I once used at work) is *slightly* approaching overkill for this application!

Reply to
Tim Watts

This, being the most sensible and reasonable suggestion, will be summarially rejected by the Chris Glur troll in one or more of the following ways:

1) simply ignored; 2) an unnecessary 'wal-mart' travel required (never mind how the troll came to obtain a rPi in the first place); 3) too much of a ballerina foo-foo answer; 4) etc.
Reply to
Rich

The unit is inside. The antenna can be outside. The antenna can be waterproofed easily. In either case one would need a wire coming in to the RPi from the gps unit. Mine works fine with the antenna mounted inside a window facing east, through a bunch of cedar trees. The OP said it was inside a box in a remote location.

Reply to
William Unruh

Well, we do not know what is "good enough"-- the OP has been very sparse with his requirements or even the situation of the computer. But yes, I would agree. For $9 it is by far the cheapest alternative.

Reply to
William Unruh

Actually most GPS report UTC not GPS time, but your system can easily account for leap seconds.

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Reply to
William Unruh

Thanks for the recommendation/suggestion.

Found it at

Reply to
J G Miller

+1
Reply to
mm0fmf

Unfortunately the link there to the sure store does not work. And on

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there is no gps receiver that I could find. However on the Sure ebay store they still seem to have them at $38. They used to have free shipping, but no longer it seems

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Reply to
William Unruh

$US 85 or GBP 50 is 'damn expensive?

The GPS35 is discontinued as are earlier GPS18s, but the GPS18x is current and comes with D-9, USB or bare wire connections and is waterproof to 1m. Available direct from Garmin for $US85.

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martin@   | Martin Gregorie 
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Reply to
Martin Gregorie

OK - I concede.

I was thinking a few years out of date and the full on mast mounted Trimble receivers - they *were* expensive!

Reply to
Tim Watts

You can do it either way.

The antennas I've seen and used have all used fairly wimpy 2mm OD cable regardless of whether I bought them as add-on antennae or they came as part of an equipment package, in this case an LX RedBox FLARM and an EW Microrecorder. The latter are respectively a glider-oriented anti- collision receiver and an IGC approved flight recorder.

By contrast the GPS35HV, a stand-alone blind GPS receiver which outputs NMEA 183 sentences, came with 2m of well-rubberised cable of around 5mm OD and is built like the proverbial brick outhouse.

There's no contest for which one would get mounted outside: the GPS35 wins hands down for sheer ruggedness.

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martin@   | Martin Gregorie 
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Reply to
Martin Gregorie

Unfortunately the usb or d-9 do not have the PPS output. You need the bare wire one for that.

Reply to
William Unruh

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