Wednesday, February 24, 2010

Solid-State Weather Systems Electronics: Part 1

This would be one of the didactic posts I'll be putting here... since we're gonna talk about electronics... but wait.. I can't be serious for a minute! So here we are breathin' and talkin' electronics like we're talking 'bout football (except I DON'T talk about football).

Let's start with the first three weather parameters which doesn't need secrecy: Ambient temperature, humidity and barometric pressure. To newbies in electronics, keep this in mind: DOWNLOAD DATASHEETS OF ANY COMPONENT YOU'RE USING, EVEN IF IT IS A DIODE!!!

Ah, I'd like to note: I won't elaborate too much on the electronic connections and circuitry because Google contains billions of 'em, including crappy ones. The best testimony that can be obtained by an electronics hobbyist is a hands-on experience, so please don't expect things to run smoothly after you've connected every terminals with that thinking that you followed a RANDOM circuit you took from Google is said to be FUNCTIONAL by a RANDOM blogger, so your circuit must work. Anyways, you'll still make that mistake everyone commits: the thought that "the circuit is provided, problem solved." so be my guest, make the mistakes, and you'll learn it the hard way.

Firstly, an LM35DZ is a simple thermal sensor which I used for ambient temperature detection, manufactured and used by the billion, so there's nothing much to it. In stores they usually cost RM5.00 (about 1.50 USD) and Farnell (an international electronics components distributor) offers much better prices.

Figure: LM35 Centigrade Sensor

To anyone using it, or who wants to use it, remember that there is a very important rule: connections! See the figure below:

Note that it is a BOTTOM VIEW!!!! I made this simple mistake and wasted a lot of time so don't mess your sensors!!
So after this, give it a supply of 5V from a voltage regulator LM7805. This'll cost another RM1.50.

Second, humidity sensors... I used HCH1000 capacitive humidity sensor, which is the hygrometer for my weather station and the cheapest by far, around RM26. See below:

Figure: Honeywell's HCH1000 capacitive humidity sensor

This sensor needs to be conditioned according to a circuit provided by the datasheet for HS1101-HS1100 here and the circuit is here:
Figure: Circuit for HCH1000 capacitive humidity sensor conditioning

You'll need to adjust the ratio between R4 and R2 and I added a 10uF non-polar capacitor in series to the HCH1000 to make the response readable by my Digital Multimeter (DMM) in frequency read mode (Buy a good DMM, not the cheap Korean or Chinese ones). Note that it took me a lot of time just to find the right links to introduce these fine adjustments so go figure if yours didn't work.

To test the sensor, put a damp cloth or tissue near the sensor, and the frequency of the timer output will reduce. This frequency'll be used to be translated in PIC microcontrollers (See Deathclaw's intro into microcontrollers in this blog if you don't know anything about microcontrollers here) or you can visit this page: Nigel's PIC page.

Third part: Barometric pressure sensors... I chose the cheapest one, MPX4115A available with a price of RM39.00 by Farnell. This sensor is very simple but the documentation regarding it sucks in the 'net. Don't look at the the datasheets if you're figuring out the pinouts, they'll confuse you with three 'styles' of terminals... see this figure which is painfully extricated from a book by Ibrahim Dogan:

Figure: MPX4115A pin descriptions

This sensor detects changes in barometric pressure, translated in outputs of voltage, so it's simple because its output is from 0-4.8V for a supply of 4.75-5.2v (plug-and-play component, no amplification needed).

For what's worth, I've presented 6 months of research (finding each sensor took a lot of time!!) and labor where the simplicity of these things are evident. Mistakes have been made and rectified, so I hope this'll pave an easier route for weather systems' researchers who wanted to build a solid-state weather system on their own.

Alhamdulillah, all this experience is very humbling to me since the more work is poured, the more I realized how much I didn't know about the complexity and beauty of electronics in the human body (no one has been able to explain why images in the brain, in the region of nanovolts doesn't get mutilated in the presence of even the strongest magnetic fields like in MRI- Magnetic Resonance Imaging machines, where electronic cameras get fuzzed easily with Electronic Jamming devices.) Masya-Allah. This is also the case in weather systems, even with the advancement in technology nowadays, weather prediction are always done with a certain amount of certainty, but it is never certain.

I'll cover the more powerfully complex parameters for the electronics in the next part, which is rain precipitation, wind speed and wind direction. Stay tuned with Vortex Electrica!!!!

Allah has made Vortexes ubiquitous in nature!



  1. Nice post. I'm sure this will help a lot of electrical meteorologists out there ;)

    check out my vortex generator! (or flower generator, whatever = P)

  2. nice!! post some of the details here bro.. open a programming dept in this blog for our fellow countrymen to read..


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