Solar Tracker Panel using LabVIEW?

Question

Good Morning,
I am required to build a simple circuit using LabVIEW that will control a single axis solar tracker in the following way;
- The solar panel will operate on a single axis only
- The solar panel will use 2 x Osram BPW34 photo diodes, one placed either side of the panel
- The diodes will operate the panel until both photo diodes are conducting the saem amount of light
- This will be monitored every (short period of time)
- The LabVIEW model needs to be connected in some way to the model. I have use of ELVIS boards
I have used time to meet with representatives from NI but I am still struggling to build the model.
I could really use some help on this as I have a deadline to meet in 1 months time. I need to know the best way to interface the system and have a running prototype. I am building the prototype now and the circuitry is the final piece of the puzzle. Is there anyway somebody could help?
Best Regards
salisbm4

Answer 1

I doubt I can help with specifics (since I've not worked with the equipment you've mentioned) but here are some general tips to consider.
1) This type of tracking system is based around the idea that if both sensors are pointing directly at the sun, they will read the same value.  However, if they are both pointed away from the sun, they will both read a diminished amount (it's hard to say how the panel should move unless you can measure a distinct difference between the two).  I'd recommend using 3 photodiodes with the center diode mounted normal to the panel and the outer two angled away slightly (the diode reading the highest value is likely the one pointed closest towards the sun so you can infer which way to move -- center should read the highest).  All this may not really be necessary though since the path of the sun is rather predictable.  You could easily use a single photodiode if you are only concerned with maximizing the reading (since each movement through the day will be rather small)
2) Beware Temporary Shading!! Parital cloudy conditions can  throw off your model if with your photodiodes are spaced apart (one is shaded and the other is not : be careful here).  Any nearby trees/power lines can also cast a shadow in different parts of the day.  You'll want to be careful about making hasty judgements or your panel will move away from the sun only to move back later when the shadow is gone.