iButton Thermochron

iButton Thermochron
Hi, and welcome to my first review for Icrontic. I work with my PC right next to me, so noise matters to me almost as much as speed. In coming weeks I'll be looking at various fans with regard to noise and efficiency, and attempting to build a silent (but still plenty fast) PC. Hope you enjoy this and the reviews to follow.

The iButton "Thermochron" is a temperature-logging device. It's tiny, as you can see from the picture taken against a CD. Built into this button-sized package are a battery, thermometer, data storage, and a clock. The metallic case is tough, it's safe to stand on, play hockey with or get wet (but not submerge). Projected battery life is about ten years.

To use the device you connect it to a PC (using the "Blue Dot" interface, also pictured) and configure it using the software provided. A data gathering "mission" is created using the wizard that goes through the following steps: ("Data rollover" means that iButton storage will be used as a circular buffer, when the buffer is full each new reading will replace the oldest one.)

Then you collect your data by placing the iButton in the location you want to measure. When you want to view some results, connect it to the Blue Dot again and view the results. The web site suggests many uses; I have used it to fine-tune cooling in my PC case.

This morning before starting the PC I opened the case and sat the iButton on the back of my video card - the first readings are before I turned the machine on, so that's ambient temperature. I disconnected a fan so there would be some change to make to show temperature measurement.

The case is a Cooler Master ATC201. In the front I have two 80mm fans blowing over the drives, at the back I have another 80mm and in the top another 80mm. I started out with the rear fan off but all the rest on. The first readings show the temperature rising as the PC starts up, to a high of about 97. The temperature change at around 7:38 shows the effect of opening the case, unplugging the top fan and starting the rear fan - obviously the rear fan is more effective, because the temperature has dropped to a steady 93 by about 8:04, when I turned on all the fans. That top fan isn't helping much - it drops the temperature by only about two degrees, (the second flat section of the graph). Finally at 8:20 I started cpuburn, bringing the temperature back up. And of course you can see the cooling down when I take the iButton out of the case to get the data from it - it doesn't stop, just keeps on measuring. Out of the case the readings drop to ambient again, about 72 degrees.

These results suggest that the top fan is essentially useless - it's using power and making noise but not cooling, but measurements around the CD drives at the top of the case might show a different story - you have to look at the whole picture before yanking fans out. In a complete test I would use perhaps five or six test locations.

If you get one of these things you can identify which fans are useful, or which you can run on 7 volts rather than 12, and make your machine as quiet as it can safely get. You can adjust airflow to cool any hot spots you might find, because the iButton is small enough to place almost anywhere. You could also use it for testing drives, seeing how hot particular models get during operation. The screenshots show that you can get the data in many forms, including histogram and as raw numbers for export to other applications, like Excel.

I don't have any real complaints about this device. I would have liked the ability to measure temperature at intervals of less than one minute, and I only need one interface on the Blue Dot. Also I would prefer a USB interface (had to go into BIOS and turn the serial port back on), but these devices are aimed at embedded engineers, and embedded engineers hang on to old technology - they use the cheapest (and slowest) thing that can do the job.

The iButton DS1921 Thermochron evaluation kit (iButton and Blue Dot) costs $25 from iButton.com. It's not for everyone, but if you're serious about keeping your case cool and quiet it can help. And, you'll probably find more use for it than just the PC. Although I don't recommend taking your own temperature with it, or your dog's.

Pro's: Con's
  • Easy to use
  • Long battery life
  • Extremely tough
  • Affordable
  • Requires a serial port
  • Frequency measurements of 1 minute
Final Thoughts: Definitely the cheapest and easiest way to tune your case cooling.
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