Saturday, January 9, 2010

Tektronics 453

Just got an old Tektronics 453 Oscilloscope that was going to go in the garbage!! Looks great and it works! which is the most important part! now I can finally check the hall effect sensor I got in Taiwan when near the water meter to see if I can detect the parts rotating inside the meter. At this moment the signal is smaller than what the Arduino can detect, and I would like to see the signal before starting to build an amplifier - also to know how much amplification does it need!

It came with 2 probes, nice old ones, one from Phillips and one from Tektronics! I think there are some more goodies where this one came from (my wife got it for me from the lab at her work), but I don't know what they are yet (my wife has no idea what these things are, or what they are for!)
Out to try out my new toy now!!

Tuesday, January 5, 2010

Weather station

The Weather Station is finally complete! That is at least the beta stage!
(the beginning of the development was a long time ago)
Here is a picture of it standing outside:

It has been there for a few weeks now, since the 13th of December, enduring the snow and ice that this winter has brought us, sending a packet every 10 minutes.

The station is based on a JeeNode, with a LDR to sense the daylight, an SHT11 to sense temperature and humidity, and a home made anemometer to sense the wind speed. Here are some photos:

Complete setup, fits nicely inside an electrical box fit for the outside.

Details of the main box. The JeeNode is visible on the left. I had to take about half a millimeter from it in order to fit inside the box. I painted pin 1 of each port with tippex and put a dot in each of the ports to know which one is which as I kept having to refer to the datasheet. The whole thing is powered by 3 AA Alkaline batteries. The wholes that lead to a sensor are covered with corks to prevent water from coming into the brain of the station..

Detail of the light sensor: an LDR. The window I made by warming up a package of hard(ish) plastic and pushing it into the whole using a small spoon. All the electronics for each of the sensors are near the sensor itself, and only 3 cables leave the sensors: Vcc, Gnd and signal (except for the SHT11).

Detail of the SHT11. This one is floating, protected inside a little cheese box, painted white using tippex (I was too lazy to use proper paint...and it was cold outside to use it anyway...and the tippex was right in front of me...and I don't use tippex for anything...)

Detail of the anemometer. I used the center of a CD spindle, attached 3 half's of ping-pong balls, and improvised a bearing from a VHS recorder roller. It fitted nicely in some electrical tube. The sensor is a optical emitter/receiver in the same package. It has not been calibrated, as I only need an indication of the amount of wind, in order to automatically lift the sun screens.

The nice thing is that I initially built the sensors to work with 5V, as I always used arduinos, then the JeeNode uses 3.3V, so I thought I had to adapt some things...not for the light sensor, as it is a basic divider, but for the optocoupler. But I tried it, and it worked fine even at 3.3V!

I spent a lot of time fighting with low power modes of the JeeNode, and finally got it to some sort of power down...which I believe will allow it to work for a few months from the batteries...lets see...I will try to make a post about that soon, as it is also of interest for the JeeLabs community.

So far it has sent 3271 packets. Here are the latest ones:

3267 1 0 0.5 87.4 @ Tue Jan 5 21:26:58 2010
3268 1 0 0.5 87.2 @ Tue Jan 5 21:37:17 2010
3269 1 0 0.5 87.3 @ Tue Jan 5 21:47:37 2010
3270 1 0 0.4 87.6 @ Tue Jan 5 21:57:57 2010
3271 1 0 0.3 87.6 @ Tue Jan 5 22:08:17 2010

The sequence of numbers corresponds to: sequence number, light level, wind level, temperature in Celcius and relative humidity in %.

I have now to put the JeeLink receiver in the server to be able to put all data into a database and use it for something useful!

(2 posts in a day! great! it must be the cold outside...)