Humidity Indicator Cards

A pack of humidity indicator cards arrived from far-off Pennsylvania and work just about like you’d expect.

The silica gel really does pull the interior of the Basement Safe down below 15%:

Humidity Indicator card - 10 percent

Humidity Indicator card – 10 percent

The dehumidifier struggles mightily to keep the rest of the basement around 50%:

Humidity Indicator card - 50 percent

Humidity Indicator card – 50 percent

They’re not dataloggers, but I can now keep an eye on more locations…

  1. #1 by Joseph Chiu on 2013-08-19 - 17:54

    Have you ever looked at Dallas Semi’s thermochron’s with the humidity option? Pricey, but self-contained and runs for years.

    • #2 by Ed on 2013-08-19 - 20:53


      Those things run $100 each: you have obviously mistaken my toy budget for a suitcase stuffed with unmarked currency! [grin]

      On the other paw, the Hobo datalogger equivalent to the ones I’m using is around $130.

      If I were in the market, I’d prefer the Dallas / Maxim button: their data format seems well-documented and isn’t locked to a goofball Windows-only program.

      There was an unsuccessful Kickstarter for a nominally cheap temp/humidity datalogger, but … it’s a specialized market.

      • #3 by madbodger on 2013-08-28 - 08:09

        I’ve worked with the Dallas “one-wire” protocol (I’m pretty sure their buttons all use it), it’s pretty simple to bit-bang, at least on a sane processor. In my case, I had to do it with a DSP that didn’t really grok anything other than its 36-bit words, so it was a little tougher. Somewhere I have a couple of the button-to-DB25 adapters, I saw ’em at a hamfest and the seller had no idea what they were.

  2. #4 by Joseph Chiu on 2013-08-29 - 03:35

    You can find them for a little less than that ($85 in onesies – $50 in K-sies) but, yes, they are pricey! I have their non-hygro brothers currently on a “mission” (as Dallas likes to call the data-collection runs) from China. They are really nice – I was first introduced to the iButtons when I got a Segway, and later incorporated 1-wire products on a few designs I’ve worked on over the years. I’ve used Hobo’s before, but the iButtons run longer on battery than the Hobo’s IIRC. The smaller iButton form-factor (about a piece of a mentos candy) is an extra bonus.

    • #5 by Ed on 2013-08-29 - 08:32

      the iButtons run longer on battery than the Hobo’s IIRC

      And when the battery goes flat, you toss the whole iButton and start over; I like the size & shape, but not that part. Of course, the size & shape dictate the battery capacity & disposable lifecycle: they solve different problems than the ones I have.

      currently on a “mission”

      Love the terminology: HOBOware has you “deploy” their loggers. Cuing Secret Agent Man on Turntable 2…

  1. Monthly Science: Silica Gel Status Report | The Smell of Molten Projects in the Morning