Quote:
Originally Posted by wilfor03
Appreciate the heads up on the LDR's and the heat....gonna try it and see what happens....gonna do some searching on the internet and see if/what other people have had problems with and how they may have fixed it. I'll keep ya posted......thanks Rich...............Bill  |
Okay Bill,
What's the good word on your tracker? Got it working yet?
Mine was great with the new LDRs, but yesterday it started acting up.
It was falling behind. The shadow stick showed me the tracker was lagging.
I checked the voltages on the LDRs and they weren't falling below the Ref.
So, I pulled the board, pulled the 10k pot (radio shack) and installed a 20k pot.
I increased the Ref voltage up from 1.23v to 1.5v and got it tracking,
but with relay chatter again.
It was a nice day, not too hot and the LDR head only 80F..
I think one of causes of the instability is the changing +12V supply.
When the motor comes on, it drops the voltage on the battery just slightly.
That drop, is noticed by the Solar charger and it comes on, placing a charge
voltage on the battery, which slightly Increases the +12V supply!
Of course this up&down of the +12V caused the Ref voltage to change just slightly.
And the LDR voltages jump up and down too..
What stays the same is the Sun, and it's effect on the LDRs.
I put a 47uf across the 12V input to the PCB, but no joy.
Tried adding some 0.1uf tantalum caps across the LDRs, hoping to slow
down the voltage changes. But I got back-n-forth motor oscillations again.
(Due to over-shoot & correction reverses).
I'm now thinking about adding a zener diode to the ref divider, to make
that voltage stay put..
I also found some really nice LDRs in my junkbox. They get down to
much lower resistance than the MTM LDRs.
In the sun, one went down to 25 ohms and other one stopped at 38 ohms.
The MTM LDRs are up around 100 ohms in bright sun..
Anyways, I reset the ref voltage to 1.35v this morning.. Maybe today it will work better.?.
Cheers,
Rich