First sensor

Hmm, this afternoon at the lab was a bit frustrating. As a starter a lot went wrong with the purchase of the two AppliedSensor sensors and the temperature sensors. My order went wrong, twice. It was a national holiday on Thursday so I feared that the stuff wouldn’t be in by Saturday. But finally, at 19.30 on Friday the box arrived. I now have a cute collection of rabbit droppings 🙂

From left to right: multi gas sensor, CO, O3, lower row: NO2, temperature.
But they aren’t that cute to work with. They worked at a different voltage than the Arduino(NO2, CO – 2.3V and O3 – 6V). So I needed different parts which weren’t available. The voltage creates the right temperature for the sensors to work and that’s critical. So the only sensor left to work with was the LM75 temperature sensor which works with the I2C® interface. This is supposed to be very easy to work with but for me as a lay person it’s still complicated. Paul found a tutorial on the web for connecting it to the Arduino. Everything works fine except that the temperature is always zero degrees. I think it’s just some minor thing we overlooked because it was already late in the afternoon. But it’s a shame that I can’t bring a working sensor back home.

Update Sunday 19:16. Yes, I got it working! I think I made two mistakes in the wiring. One very basic one, I forgot to attach the sensor to the 5V *blush* and I mixed up the two wires coming from the sensor. I reread the tutorial: ‘Using the Wire library, the Analog Input 5 is automatically set up as the SCL line’ and I now put the data wire SDA, in 4 which works fine. The temperature does seem to be two degrees too high…