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Logger Mini on the John Muir Trail

Logger Mini and I returned this week from the John Muir Trail. It was an amazing, epic trip, ending unexpectedly with me stranded in the middle of nowhere in the Owens Valley desert, gawking at the PLAGUE WARNING signs. It took me two days to get out, but I’m back home now and plague-free.

I used the logger quite a lot during the trip, and it worked like a champ. After a couple weeks of real-world use on the trail, a few points become clear:

  • The trip timer feature (using a vibration sensor to detect movement) was totally pointless. It worked fairly well, but didn’t add anything of value, and I never used it even once. I’ll delete it and the associated hardware from future designs.
  • Graphs going back more than 12 hours were also pointless. I never looked at them. That’s great, because it takes a lot of memory to store the sample data further in the past. I’ll delete the extra external EEPROM from future designs.
  • Temperature measurement worked great for determining overnight lows, but not so great for highs or current daytime temperature. Inside its case, or in my pocket, or in the sun, it almost always showed a temperature that seemed unrealistically high. Maybe replace the minute-by-minute temperature graphs with daily high/low/avg stats instead.
  • Where the logger really shone was the display of current and recent altitude. When we knew we were climbing towards a 12100 ft pass, and had been going for what seemed like hours, it was cool to pull out the logger and see exactly where we were and how much climbing was left.
  • The screen was difficult to read in direct sunlight, where difficult means “impossible”. I knew this already, but it was still annoying.
  • Reliability was excellent. I never experienced a single problem or unexplained reset on the trail.
  • Battery life was excellent. My prototype is still on its original AAA battery, and the battery voltage has barely changed since I first installed it.
  • There’s definitely a place for the logger, even in a GPS world. I also had a GPS along, but the logger is 20% of its size and 10% of its weight. The GPS chewed through batteries, had difficulty getting an accurate position fix, and exhibited poor alitutude accuracy even when it had a fix.

Overall, bringing along the logger was a clear success. So, what next? My inclination at this point is to share all the hardware and software design data, and try to get some additional people interested in improving the design further. I think there’s a place for both the Logger Mini and Logger Classic. The Classic is all through-hole parts and can be assembled in about an hour. The Mini is smaller and cooler, but more challenging to assemble. While the underlying hardware is different, the programming model is nearly identical, and the same software can be compiled for either device with only a few device-specific sections to reflect the different display screens. I have a few more unpopulated PCBs of both types that I can offer to developers, or put the Eagle and Gerber files somewhere and let people do what they like with them. Anyone have any other specific suggestions? It would be great to see this grow into something big.


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3 Comments so far

  1. Keenan - August 11th, 2011 10:18 pm

    Liking this project, I feel like it’s something I’d definitely use, if I ever got around to building it. I think I’d be interested in the long-term data, and even ‘movement’ data to compare stats like elevation change vs. travel time over multiple days. The ‘mini’ already seems like a pretty tiny design, and low power too, so I think I’d like to keep those features around, or at least on the PCB and optional via a jumper or something.

  2. Ferudun - May 22nd, 2013 7:29 am

    I built your classic logger on a piece of perforated board. It works properly. However, pressure function seems some complex for me. I want to use it as a barometer and weather forecaster. For this, I entered current true altitude as 830 meters. In this case, sea level pressure on the display was equal to our local meteorological stations value.Day after (rainy), weather stations pressure felt down, loggers value followed it, but true altitude changed too. Therefore altitude graphs are changed a few ten meters. In reality, it stays on library shelf and altitude changes only a few ten centimeters in a day.
    I think, in fixed altitude, sea level pressure should change according only weather conditions, but stations altitude not.
    How can i use it as a graphical barometer/ weather forecaster ?
    Thanks for advanced, sincerely

  3. Steve Chamberlin - May 22nd, 2013 7:53 am

    The software is designed primarily as an altimeter, so changes in pressure are interpreted as changes in altitude. If you want to force the altitude to remain constant and use it as a barometer for weather forecasting, you would need to change the software. The source code is included with the other logger files if you want to do that. Or you could just ignore the altitude data, after you’ve calibrated it once.

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