From: hinsome lee
Subject: solar tracker
To: rich_demartile@prodigy.net
Cc:
Date:
Dear Mr.Demartile,
Thanks to reply my email, according to you I
had gone through some tutorial about 555 timer, now
I'm be able to understand more about the operation of
your circuit.
Somehow, there are some questions about the
circuit still, I'm not really understand the operation
of the east/west limit switch, what kind of swith do
you used, and how it's funtion?
The monostable operation of the 555 timeris
depends on it's external RC circuit, the resistor used
is 47K and the capacitor used is 3.3mF. Are you sure
about it, since accordind to the calculation, the time
delay might me 170.61 sec it's to long, about 3
minutes? Can you give the list of componets you used
for the circuit, as seen on the schematics circut?
\Anyway thanks for you help, hope to hear
from you soon.
HINSOME LEEHinsome, I'll have to check my calculations (it's been awhile) You can feel free to substitute different values to get whatever time you need. All I know is that the motor runs for only a fraction of a second in a short burst and the panel averages around 4° accuracy in tracking the sun. In regards to the limit switches, I used two cheap normally open spring-loaded push buttons to "ground" pin 4 of the appropriate 555 chip to prevent motion in "that" direction. The motor is free to run in the opposite direction even when the limit switch is activated in the opposite end of travel. I updated my web page last night so you should find more useful information there now. And thanks for your interest and comments. Feel free to inquire for more info when needed and I'd like to see your finished project when done. I'm sure there's several things you can come up with to improve my design. For instance...the bird house was built mainly to make my wife find it visually appealing in the yard, but the electronics get wet in damp weather. If I built another one I would probably use weather-proof 110volt outdoor boxes and conduit to keep everything dry (hint). The tracker is currently up in the California Coastal Range mountains at 4,000ft elevation keeping my 300 amp/hr battery bank charged up through the winter. I keep the tracker turned off when I'm not there to prevent causing a forest fire. I live in the San Francisco Bay area.
Stay in touch,
Rich DeMartile
From: rich_demartile
Subject: Re: Solar tracker
To: Cdolberg@aol.com
Cc:
Date:
Question was (I lost the original)
From Carl...Tell me more about how the tracker is built?
Hi Carl,
As you have guessed the drive mechanism is totally simple and you probably have everything at home already. How you go about the design is pretty much up to you. Maybe you're familiar with building coasters with rope steering when you were a kid. (A steering wheel attached to a broom stick supported between two vertical boards. A rope is wound around the broom stick and attached at each end to the 2 x 4 front axel) I don't have a sketch, but I'll try to give an accurate description:
Any old battery powered drill motor should work with a small diameter driver bit in the chuck to be used as a friction-driver. (my bit has approximately 3/8" diameter and is serrated on the outer surface) I gutted the internal batteries and hard wired my 12V supply directly to the motor as the schematic shows.
A perfect 5" circle cut out of a piece of wood (3/4") thick was used to obtain further reduction. At the center of the circle drill a hole for a pressed-fit (or wood glue fit) to whatever diameter dowel material you have on hand (I used 1/2" because the ball-bearing size is easy to find at a hardware store).
Now the wooden disc is attached to the shaft as a driver via the tight fit or glued, then the dowel is flush-cut off on the face of the disc. Now the more critical part comes into play and is hard to describe but totally achievable via trial and error. Accurately measure the following diameters...
The finished disc OD
The bearing outer race OD's (2 bearings are used)
The drill motor housing diameter at the right spot near (but behind) the chuck at such a spot that the driver bit will protrude the right depth through a piece of 3/4" wood (fencing board) to accurately rub (drive) the disc which is also supported by the same board via the (inboard ?) bearing pressed into the board. Now I'm going to pause here for some insight into how I arrived at this.
First sketch out the design with no measurements for a conceptual view
Then on a fresh piece of paper use a compass to lay out all the center to center points for proper placement of the holes so the drill motor meshes properly with the 5" disc. Lay out the support bearing diameters to be concentric with the 5" disc circle
Carl... at this point I'm going to stop and look for my old layout paper I used. I'll try to scan it and send it to you later on as a JPG/tiff/gif or whatever you can use. I do have autocad if you support dxf/dwg format.
This is getting too involved trying to describe how it's done.
(I'm glad someone else finds this simple design interesting)
Later,
Rich DeMartile