View Full Version : E-map GPS stress testing
01-27-2004, 11:16 AM
Just incase anyone is interested....
The Garmin E-Map temp range accourding to the manual has a bottom end of 5F
I put 1 hour on it in open cockpit at 30F, one hour at 27F but when it got down into the lower twenties ( wind chill = -13F ) it finally locked up after about 15min flight time. It would not reset until I landed and removed the batteries.
Now that it warmed up it is working fine again. It even remembered the data from the first 15min of the trip.
Fortunately, I never depend on the GPS and use it mostly for groundspeed FYI. Though x-country ( if you can call ultralight flights x-country ) I carry a spare EMap in my pocket.
01-28-2004, 03:58 AM
The wind chill value only applies to exposed skin, where evaporation of moisture can occur. Wind chill doesn't apply to electronics. Your GPS should not have locked up at 27 degrees. Now I have seen where the monochrome LCD displays would not function when cold since LCD's rely on heat to turn on the pixels. Could this have been the case?
01-28-2004, 06:05 AM
The LCD was still displaying clearly however, the logic was not. It would not accept any input from any buttons including the power button. The display did not update and showed time and position of 4:16. I took off at 4:00. Removing the batteries shut it down. Upon revival the log showed all data from 4:00 to 4:16 but nothing after.
Granted the gps has no skin and does not release moisture but would not air movement increase the rate and amount of cooling? If so this may cool the processor better than one in a static environment at the same temp? Otherwise I could just take the fans out of my computer and off of the heat sink.
01-28-2004, 10:33 AM
Sounds like the processor did lock up.
Air movement will increase the cooling rate such as when you blow air across a heat sink, but the surface temp will never be less than the air blowing across it. With a heat sink, you are trying to dissipate unwanted heat, not cool it to a temp less than ambient. That's not to say that 35 degrees isn't a bad thing for a processor. I have read where some home-brew style experiments were tried where some young computer geek super cooled his processor with nitrogen (not a full blast obviously) so that he could over-clock his home computer to some outrageous speed, of which I can't recall.
It's a different situation for your GPS because your GPS doesn't need a heat sink and a fan on the processor to dissipate excessive heat. But like I said above, colder than average isn't necessarily a bad thing. At the temps you stated, your GPS should not have locked up. If I had to guess, I'd say that the -5C spec is the bottom limit of the display. Typical solid state component specifications are well below zero. A commercial rating for silicone based electronics is going to start well below zero degrees between -20C and -40C, with a high end of between +85C and +125C.
Here are a few parts that I picked at random.
Now here's a Digi-Key page on a LCD module (look near the bottom of the page).
Notice the operating temp range. Most of them are -5C to +50C. Your temp of 27F is equal to -2.77C. With a tolerance of as much as plus/minus 15% on some electronics, the -5C spec can be as high as -4.25C (+24.4F). That's less than 3F degrees between your thermometer reading and your (my guess) LCD display spec. I wonder how far off your thermometer is.
After looking at the display driver spec, the electronics seem to be temp sensitive for some reason. The device could have locked up and intern, locked up the rest of the GPS. That's my guess.
01-28-2004, 11:54 AM
The processor would typically like to be cooler but other components may not like it. My assumption is that the rated temp was based on a 'normal' rate of cooling and 50-70mph wind may dissipate what little heat the components generate causing them to cool far more efficiently. As you have found the manual may not even be correct for the tolerances.
I am one of those geeks that used to over-clock CPU's but now-a-days it makes little difference since the major bottle neck is the bus speed and the only way to alleviate that problem is more 1st and 2ondary level cache.
My temp source is the weather station located at the airport which as 10 miles away from my location and 1000 ft below it.
01-28-2004, 12:04 PM
An additional thought...
Does anyone know the effect of temp on alkaline cells?
01-28-2004, 05:57 PM
My cousin is a computer nerd and he has made his computer liquid cooled! It has a small radiator and fan and hoses that connect it to a water jacket around the processor. Said he gets twice the speed out of the computer this way.
01-30-2004, 08:58 PM
I read somewhere, sometime, that someone velcro'd their GPS to their thy (kind of like a kneeboard). I wonder if that would help keep it warm. I have personally noticed that in the winter, my Emap mounted up near the front windshield of my car will have VERY short battery life. In fact, if I warm it up for a while it will come back with everything OK. I can think of no reason for the electronics to 'lock up' under cold conditions, but LCD's don't like it and will stop responding.
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