Computing stuff tied to the physical world

Room Board update

In Hardware on Oct 31, 2009 at 00:01

Here is the latest version of the Room Board, just in:


It works for all combinations of SHT11/DS18B20, PIR/EPIR, and LDR. Here’s SHT11 + PIR + LDR:


And here’s a setup with DS18B20 + EPIR + LDR:


Both can be used with the latest version of the rooms sketch.

But… if look closely at that second board, you’ll see that I still got it wrong!

The DS18B20 temperature sensor is labeled the wrong way around, and must be mounted as follows:


Drat – same mistake as last time!

And now I’ve also figured out how this happened. Here is the pinout shown on the Dallas Semiconductor / Maxim data sheet:

Screen shot 2009-10-30 at 14.43.29.png

B o t t o m  view. Doh!

I’m going to declare victory anyway, and call these boards final. Even though this issue will have to be documented and spelled out everywhere to prevent people from falling into this trap. I have 100 room boards, and I simply don’t want to trash them and wait another 3 weeks. Most people will probably use the SHT11 sensor anyway, where this issue is irrelevant.

Available in the shop now. Foul-ups happen, so be it. End of story.

  1. Hi J-C, the sht1x sensors are uncomfortably expensive, by chance have you looked at any alternatives? I see many mentions of china-made hs1101 sensors, going for about ten bucks. any experience with these?

    • i’m afraid not – it looks like the HS1101 is a variable capacitance, used to drive an oscillator. The measurement then consists of determining either the frequency, or the voltage when sent through a low-pass filter.

      The room board isn’t set up for this, but I did put the DS18B20 temperature sensor on the DIO pin, leaving the AIO pin available for reading out another (analog or digital) sensor signal. Maybe some trick could be used to charge/discharge the HS1101 capacitor directly through the ATMega I/O pin, and measure an RC time constant, for example.

      The HH10D by HopeRF (same manufacturer as the RFM12B radio) is another option. It generates a frequency – it also has an EEPROM with some parameters which needs to be read out over I2C, but this could be done once and then copied to the JeeNode’s EEPROM or flash memory.

      Both solutions require a bit more effort than the SHT11. I’d be interested to hear whether anyone gets something like this working, or whether there are other alternatives. The SHT11 is a nice sensor, but I agree.. at nearly 24 euro excluding VAT it is a bit pricey (Farnell price).

  2. The SHT11 is listed at £15 (about 17 euro) + VAT at farnell uk Still a bit pricey but better than E24.

  3. Hi! CSD-Electronics also got some SHT11 beside some other nice stuff. search for SHT

  4. Hi, i have tried the room board with an DS18B20 and an LDR (LDR1 position). The LDR doesn´t work, because it is attached to port 4 and the sketch assumes port 1.

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