Solar Tracker Project

[Xringer]

Hey! Radio Shack stays open until 9PM around here.. I picked up some of their cheapo LDRs and will try them out tomorrow. They look mediocre on the ohm meter. We'll see..

I also installed some old reflective tape inside the glass window. I covered up about 70% of the
surface area, leaving a 30% slot. That should be enough, if I keep the elevation set close to the correct posistion.




There are some heat sink fins on the back-side of the ex-lamp module,
so maybe cutting the window size by more than half, might lower the temp.

Back when I was looking around on the web, I found out that some guys
had partly painted the faces of sensors that were too sensitive.

Edit:
17:30 6/22/2010
The radio shack photocells don't bring the voltage down enough under bright sun.
(Their resistance is too high.. Very close, but no cigar).
I tried installing some resistors across them, and they kinda worked a little.
But it was over-cast a lot today and it's going to be rainy tomorrow..

Looking at the circuit board, the two 1K pull-ups (for the LDRs), are located
in a nice clear area of the PCB near the "Mounting Hole".
It looks like one could replace those 1k resistors with a Pot (and series resistor)
and be able to match just about any old LDR to the board.

[wilfor03]

That might be the ticket......Gonna try it? I got my board finally mounted and hooked up. The panels were sitting at about 3 o'clock position and when I fired up the board, it went right down to 5pm where it should have been. Getting a bit of relay chatter just before it finally moves. Shuts right up after the move. Guess thats gonna be the sort of "norm" till I get a 10k pot to stick in there. Just keepin ya posted...........Hope ya get yours fired up again (reliably, that is)....Bill

[Xringer]

I got a lot less relay clicking when I had the caps across the LDRs.
I took them off, because they would sometimes cause an over-shoot
and make the mount go back-and-forth a few times, with little over-shoots. Oscillation..
But, they were large caps, and I think maybe a smaller cap might work much better.
Maybe a 05. to 1 uF would quite it down some.?.
The idea is to smooth out the voltages on the LDR lines. Slow down the changes caused by clouds etc.


I would not replace that 9.1 k, with a 10 k pot.. It's just too close in value, and does
not give much of a voltage range. Put in a 20k (multi-turn) and get some higher voltage.
Now, I'm stuck under 1.25 volts, so the LDRs have to really get down low to work.
IIRC up around 1.65v worked okay on most days..

Nope, I will not be replacing the two 1k pull-ups with pots. I'm going to sit back
and wait for the new LDRs to show up and get it running like it was a few days ago..
It's going to be rainy here until Friday anyways..

Cheers,
Rich

[wilfor03]

okay, cool beans then....I'll see what little caps I've got in the parts bin and play around abit.....as soon as it got dark, the panels just started moving back to the east and just awaitin for the early morning sun now. That's so neat to see to see this thing movin on its own.....reckon I'm really hooked now!! Bill

[Xringer]

LOL!! Now you don't have to stay home and move the array all day..
You can go see a movie or to the beach!

I've got those resistors across the radshack LDRs, so my board thinks is always daytime.
I had a jumper to short East LDR to make it go E, but decided to leave it dead-center,
in case the forecast is right..T-Storms coming..

[Xringer]

The new LDRs came yesterday. Got them installed last night and the tracker is working great today..
I added some reflective tape to the outside of the glass window, in the LDR module.
Now, there is mirror tape on the inside and outside of the glass.

The temperature of metal in the shade of the panels was 90F today, and the
LDR module wasn't very much warmer. Every time I checked, it was under 92.
(My skin was warmer)..

It was a bit hazy today and cloud cover really rolled in about 15:30.
There was a 22 degree increase in water temp today. 8AM to 3:30PM.
After my quick shower this AM, the water was at 96F, now it's 118F.

My thanks to Michael at MTM Scientific. He got the replacement parts
right out to me very quickly (First Class Mail).. No charge!!

Cheers,
Rich

Edit: June 27, 2010

Many times, I could not see the shadow of the Shadow stick..
It fell on the mount, below where it could be seen..
So, I mounted a white plastic disc on the stick (a 1/4:20 threaded rod).

So today, I could easily see the shadow on the white Teflon surface, but there
is one problem.. NO Shadow! The tracker is so accurate, the shadow is nowhere to be seen!

I know it's still around, because I was out early this AM, before the tracker started moving..

[nibs]

Since the sun is very predictable in its path, why not just use a timer to advance the array X degrees every Y minutes?

[Xringer]

Where can you buy one (that's less expensive than an active tracker)??

I could probably build one, if I wanted to built and program a micro-controller (with a RTC)
and figure out how to use the pulses from the tracker actuator (mover-motor)
as feedback to 'know' where the array is pointing. I can imagine the calibration process..


As a person that has worked on all kinds of tracking antennas over the last 40
years, I inclined to say, this type of (active) tracker gives you a lot of bang for your bucks.

The less complex a system is, the more likely it is to work longer..

One other thing just occurred to me.. At 6AM, on a day when it's raining and overcast all day.
When T-storms with high winds are passing,
Would I really want my array tracking the sun (behind the clouds) all day long??

Kind of a waste of battery power. After a few days of rain, my little battery would be flat..
(It relies on it's own little 10w PV to stay alive).

[nibs]

My newer panels are pretty good at making power on cloudy days, so it may pay.
A couple of years ago, there was a guy at Quartzsite AZ selling a beautifully made well engineered tracker for around $2,000 but at that price it was far cheaper (not as elegant) to just add another panel or two.

[NiHaoMike]

What about use a BEAM robotics circuit that does not require any batteries? Use bigger ratios so the motor can be smaller. Then design a circuit based on charging a capacitor from a small solar panel, then periodically discharging it through the motor in the right direction.