Tracker leading the sun

buck-canuck
buck-canuck Registered Users Posts: 9 ✭
in General Solar Power Topics #1
This last summer I built a tracker using a old sat dish. Bought a LED3X24 from Redrok. Everything worked great until today. It's the first sunny day in the last week and my tracker has been leading the sun all day by about 25 degrees. As of right now (1:30), it has gone to west extreme. I went out earlier and taped up the lower 3/4 of the glass housing thinking that it might be getting a glare from the rounded end. No luck. It has been rain and wet snow for the last week, could moisture have built up in the circuitry? Has the sensor gone bad after 4 months of use?
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  • Joe_B
    Joe_B Solar Expert Posts: 318 ✭✭✭✭✭✭
    #2
    Re: Tracker leading the sun

    Sounds like the gain has shifted. How high are the valuues of the gain setting resistors? If they are very high, then moisture could affect things.
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  • buck-canuck
    buck-canuck Registered Users Posts: 9 ✭
    #3
    Re: Tracker leading the sun

    I must admit that I don't really know what you mean. I never adjusted anything, only installed the LED3 and it worked fine until now. Is the gain on the LED3 or the actuator?
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  • Joe_B
    Joe_B Solar Expert Posts: 318 ✭✭✭✭✭✭
    #4
    Re: Tracker leading the sun

    The gain is the overall closed loop system gain. You have a feedback loop which servo's the motor to maintain equilibrium between the two photo sensors. I took a look at the schematic on their web page and there are some pretty high value resistors in that circuit that could indeed shift their values if moisture or contamination got in. Other causes could be the aim of the photo diodes (LED'S) or reflections. Using LED'S as photo detectors is asking for trouble due to temperature matching issues. IMHO that is one hokey circuit but that is a topic for another discussion.
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,022 ✭✭✭✭
    #5
    Re: Tracker leading the sun

    I had a redrock sensor on a similar setup (old satellited dish hardware), since swapped out for an Analogue guy unit. Both work fine, but the redrock needed more tweaking.

    If there was snow on the ground to the west of the array it would sense that as the brightest spot and be full west at 9am. What I did was put some black electrical tape on the bottom of the baby food jar that housed the redrock sensor, effectively blocking any reflected light from below influencing the sensor. Worked fine after that. Just be sure that reflected light doesn't strike the big light sensors from below.

    I like the Analogue unit, it comes sealed and ready to go.

    Ralph
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  • rplarry
    rplarry Solar Expert Posts: 203 ✭✭
    #6
    Re: Tracker leading the sun

    Mine needs tweaking occasionally. I just reaim the sensor by rotating it a few degrees on its mount. Makes it look like the sensor is not aimed directly at the sun but the arrays do track fine.
    HTH
    Larry
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