GPIO Sensors Fun – Keyes DS18b20 1-Wire for the Raspberry Pi

Raspberry Pi GPIO

I’ve been using my Raspberry Pi as a replacement for another bulky server/heating element I used two years ago. Since then, the Credit Card sized hardware with it’s 8 Gigabyte SD-card, has endured the role of a NTP, DNS, OpenVPN, HTTP and SSH-terminal server. With no crashes or slowdowns (within expectable limits) to speak of, I recently tapped into it’s gracious GPIO.

With no previous electronics experience, I acquired the following:

  • Smallest breadboard I could find (tiny!)
  • Arduino-like color-coded hobby cables
  • Keyes DS18b20 1-Wire (“Classic” DS18b20 not available locally)
  • 4.7k Ohm resistor

I wired it all up according To This Diagram (Again, no experience)

Expectations were high, once booted up, modules loaded. The directory /sys/bus/w1/devices/ contained… Nothing.
After a quick browse through the Keyes DS18b20 Data sheet, I noticed that the Signal and Power pins was reversed in relation to the “Classic” sensor. A quick poweroff-pinchange-poweron-modprobe later fixed the issue. Luckily, nothing fried 🙂

End result:
Keyes DS18b20 Raspberry Pi

Google provided me with a perl -and shell script. I added RRDtool, Lighttpd, a Crontab entry and some HTML.

End result:
Room Temp

Building: Fun
Usefulness: Questionable (At least it detects “Window Open” events)

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