Wednesday, October 24, 2012

diy anemometer

I was organizing here the other day (a rare thing) and I came across this DIY anemometer (do it yourself wind speed and direction indicator recorder) that I had built in 2002 according to Derek Weston's DIY Rotorvane excellent design. What a nice thing Derek helped me build!

I should be putting it outside but I will do that at the new place. For now it has to be put away. Should run it over the winter to make sure it still works OK? It does not really go anywhere until the spring. Hopefully this winter will be mild but there will be storms and it is a bit of a thrill to see how strong the wind got the night before, for example. I have a great tall post to mount it on which is mostly in the clear. It is in the house's shadow but the wind almost never blows from that direction (usually from the NW here).

This was a very nice DIY project for me with wonderful instructions, software and personal help from Derek via email. His webpage isn't live any more but Chris' site has a very thorough review of Derek's device.

I have just installed the RS232/USB driver and now Derek's software and manual which I'd saved on a CD with the device. It turns out that was a good idea since neither is available on the web. If you need either, let me know by email.

As I write this, I am having trouble getting the anemometer to talk to the computer thru COM1 via the RS232/USB adapter. When I spin the cups, the LEDs on the display track the movement so I can see it is responding correctly but I can't read it from the computer. It only "speaks" RS232 so I need to remember how to do that. I dropped the speed to 1200bps but that does not get it going. Update 10/27: I have it working now with a straight through RS232 cable. Not sure why the RS232/USB adapter does not like it.

By itself, the anemometer will store a months worth of readings and it can be remotely located. Here is a sample of the log in printed form that I was able to produce with Derek's software.

Ten years ago I had assembled the display easily and it worked well. There was a fair bit of fine soldering but no surface mount components which suited me just fine. Many LEDs mount in the board at the same height. It worked on the first try.

Derek's rotor assembly is particularly clever, robust and precise, all at the same time.

I was a bit skeptical of my ability to make the cups out of ping-pong balls as Derek described but I got very respectable results by simply being careful with a very sharp blade. I did a couple trial runs to get a bit of practice. The ping-pong balls were inexpensive and available anywhere thus illustrating an important principle of DIY projects - that the materials should be readily available anywhere and cheap to obtain.

Derek had a great small kit of the circuit board and some of the special parts like the machined spindle and the disk but I am assuming that is no longer available. Derek had explained on his website when you could see it that he had sold the rights to the design to a business and that there were a limited number of the kits available.

Derek, if you are sailing out there somewhere and want to say hello, please write to me! This was a great project - thank you. Nicely done.


Monday, October 01, 2012

reader project

Bruce from Florida about his solar concentrating hot tub heater which he built after reading my book:

Hi George,

Thanks for the compliment. I stand on the shoulders of giants (like YOU). {blush}

It has worked out very nicely. It actually produces WAY TOO MUCH heat in the spring and summer. It goes past 108°F and trips the hot tub's overheat safety circuit. (I'm adding a thermal sensor that plugs into the Arduino) As you can see I have it in series with a passive unit my friend built. I may bypass that in the summer and use just the array. Now that I have it working, I'm of course working to refine it, simplify and miniaturize it even more.

I'm planning on building a Tiki hut near the hot tub and putting the array on the roof of the hut facing south. That would give it at least 2 more hours of exposure per day. It will also give me my back yard view back. Right now the whole contraption dominates 1/2 of my little back yard. But what a conversation piece.

I will make the Arduino kit available eventually. I still have some tweaks to do. Right now I'm fine-tuning the routine that dynamically switches in and out of "timed mode" when it gets cloudy on a sunny day.

You probably noticed some things about the operation of the tracker movement. It never goes backwards to search the sun. That was a concept I decided to tackle when I read one comment on the internet "You can count on the sun to never move backwards". I thought that was funny and true… most of the solar trackers actually hunt for the sun moving west AND east. You are surely right— that little amount of movement east doesn't matter much energy-wise, but it still irritated me. It wasn't "elegant".

The other thing you may have noticed is the speed. My array moves way faster than others. That's thanks to the combination of the speed of the processor and the sensitivity of the garden light's PV "sensor" and the fact that I'm only moving 4 little 4-foot troughs. I'm sure the little screwdriver could not move your big array without being geared down. It takes less than 30 seconds to return east. Seeking the sun happens in less than 1 second. There's no wasted energy and a minimum of irritating motor noise and wear on the motor.

The drive setup is cheaper and more compact than yours, that was one of my goals there. The one thing I don't have that yours has is spring isolation from the motor to the array, but so far it hasn't been necessary. I think the advantage of its positioning under the array, not extending out the side makes up for that flaw.

I also the idea of putting the 'brains' in a fishbowl in the heat of the sun worried me. Here in Florida, I could imagine a china-syndrome happening. That's what steered me towards putting the controller down below, with just the "eye" up on top. Plus, I was itching to do something cool with the Arduino. What a fun and powerful development platform that is!

I will be able to eventually have the whole control system manufactured at a fraction of the size and cost. Everything is based on easily available and inexpensive components.

$20 for the screwdriver, $14 for the shower door wheels, I got a shop to cut and thread a piece of Delrin with standard 13 threads/inch for $25. The "housing" for the motor is a 2" conduit body $8. The Arduino, sensors and relays altogether cost less than $40.

I tried using my own voice on the video, but I alas, am the world's most sleep-inducing narrator. I ended up using one of the speech voices on my Macintosh and I think it adds just the right touch. I slowed it down quite bit to sound more like the real me. Also I worked on the video to add interest and humor. Version 1 without those elements was un-watchable.


You can write to Bruce via Youtube.

Some more pics and description of Bruce's project

Projects from Andrew Gray (US) and Sulaiman (Jordan) shown in videos.