Instructables

Portable Solar Tracker (No microcontroller required!)

Picture of Portable Solar Tracker (No microcontroller required!)
Ever wanted to keep your solar panel in full sun all day long without having to constantly move it?  A solar tracker may be the answer.  This tracker has the advantage of being portable - if you move it, the tracker will automatically adjust back to the sun, unlike the chronological solar trackers.  Another strong point of this solar tracker is its cost - there is no microcontroller or other expensive parts.

Principle of operation:
   To track the sun, this device uses 4 photoresistors arranged in a wheatstone bridge configuration.  A quad comparator controls movement.  One comparator acts as an oscillator to have the device turned on a small fraction of the time.  2 comparators 'decide' whether to yaw or pitch the solar panel, and the other comparator acts as an inverter.
 
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Step 1: Round up the parts

Parts List:
1 breadboard

1 L298N H-Bridge motor driver

preformed jumper wires

4 male-to-female wires (this is a pack of 40)

AWG 24 wire (for connecting solar panel to breadboard)

1 lm324 quad operational amplifier IC

solar panel of your choice with mounting holes (I used a 20V solar panel, but as long as your solar panel is between 5V and 32V, you should be fine).  If the solar panel is over 32V, you will exceed the maximum supply voltage to the lm324.  If the solar panel is below 12V, you may need a 12V battery to power the H-bridge.

1 220uF capacitor (make sure the voltage rating is greater than or equal to the voltage of your solar panel.  You only need 1 of these, even though the link shows a pack of 25).

4 2200uF capacitors.  (make sure the voltage rating is greater than or equal to the voltage of your solar panel.  You will need a capacitor with a higher voltage rating than this one if your solar panel exceeds 25V.  You only need 4, but the link shows a pack of 20.  If you want higher surge current capability, you can use all 20).

1 motorized rotating base (I used a "Hoberman Actuator" (which I believe is no longer sold).  here is a similar item  You need something that you can attach your solar tracker to that rotates slowly)

4 photoresistors (comes in pack of 20.  You only need 4 photoresistors)

1 IRF3205 N-MOSFET transistor (comes in a pack of 5.  You only need 1 MOSFET, but these puppies are fragile.  I reccomend buying a pack of at least 2 in case you break one).

4 signal switching diodes (This is a pack of 30.  You only need 4)

Resistors (You may want to buy a resistor kit if you plan to build other circuits.  Just be sure your resistor kit contains all the resistors required for this project)
   -1 100
   -4 1K
   -3 3.3K
   -3 10K
   -1 47K
   -3 100K
   -1 1.5M

1 geared motor (I used a K'nex motor.  Must have a shaft to which a string can be tied)

Wood Pieces:
   1 1/2" thick wooden board, approx. same length, width of the solar panel (From now on, this piece will be called "wood1")
   1 1"x2"xA" board, where A is about 2" to 3" more than solar panel width (From now on, this piece will be called "wood2")
   1 1"x2"xB" board, where B is about 1" more than the solar panel width (From now on, this piece will be called "wood3")
   2 1"x2"xC" board, where C is approx. solar panel length (From now on, this piece will be called "wood4")
   2 1.5"x1.5"x1/2" wood blocks (From now on, this piece will be called "wood5")
   2 3" long, 3/8" diameter wood dowels (From now on, this piece will be called "wood6")
   1 1"x3"x1/16" wood strip(From now on, this piece will be called "wood7")
   1 1/2"x1/2"x2" wood block(From now on, this piece will be called "wood8")
   1 breadboard-sized wood piece(From now on, this piece will be called "wood9")

Fasteners:
   6 1.5" long wood screws
   6 3/4" long screws
   3 bolts
   3 nuts that fit the bolts
   wood glue
optional parts:
   1 tactile button switch (This is a 10-pack.  You only need 1).  By using this optional switch, you can turn on the H-Bridge at any time without having to wait until the oscillator signals to turn on.

   1 330K resistor (must use this if you you the tactile button switch)

Tools requried:
drill
screwdriver (phillips and flat head)
adjustable wrench
allen wrench
gtoal1 month ago

How much did the tracker cost to build, and how much improvement did it give you in terms of total energy collected?

If you spent the same money on more solar panels or a larger panel, that didn't track, how much more energy would you collect?

I've not found any trackers at this small scale that are cost effective compared to just adding more real estate. They only really come in to their own on big arrays.

spencerearly (author)  gtoal1 month ago
This was quite cheap. The breadboard was $6 and the dual H-bridge motor controller was about $10. The cost of everything else was under $10 (I think) if you used scrap wood for free and scavenge through junk for a geared motor. You can look at the products for sale listed in the links at http://www.instructables.com/id/Portable-Solar-Tracker/ under "Parts List:"

I didn't do any quantitative tests comparing energy collected with vs without tracking, but I would say I got at least a 30% increase compared to moving the solar panel manually 3 times per day. Considering that my 10W solar panel was $80, an extra 30% would cost $24 extra in solar panels. So I guess I actually lost a little money.

You are right that the big arrays are cost effective, since the tracking technology used on a 10W panel can be used on a 10KW panel (but with more mechanical stability). Think about the other extreme of the spectrum - what if those little solar cells in calculators had tracking technology? So much cheaper just to add more cells!
hguzman38 months ago
Hi there, was wondering what was the wattage rating on the resistors that you used in this project. Thanks!
spencerearly (author)  hguzman37 months ago
I used 1/4 watt resistors. You should be fine as long as the wattage rating is at least 1/8 watt.
spencerearly (author) 10 months ago
Thanks. Did you build one and get it to work? I have always had trouble with the baseplate rotation and I took mine apart.
billgeo10 months ago
Thats just perfect!
Thats all you need for a good tracker.
I always thought that a micro for this job is an overkill!!!
Great instructable...