Introduction: 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.

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")

   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:
screwdriver (phillips and flat head)
adjustable wrench
allen wrench

Step 2: Drill Holes in Wood1

Drill pilot holes for the 2" wood screws as indicated by the red marks in the picture.

Any other holes in the picture do not need to be drilled.

Step 3: Drill Holes in Wood2

Drill pilot holes for the 2" wood screws as indicated by the red and green marks in the picture.  The distance between the green holes should equal the distance between the red holes for wood1 as they should line up.

Any other holes in the picture do not need to be drilled.

Step 4: Drill Holes in Wood3

Drill pilot holes for the 3/4" wood screws as indicated by the red marks in the picture.   Drill holes for the bolts as indicated by the green marks.  If the bolts cannot fit their shafts entirely through the wood, you can drill holes wide enough for the bolt heads as indicated by the green marks in the 2nd picture of this step.  The distance between the green holes should equal the distance between the mounting holes in the solar panel.

Any other holes in the picture do not need to be drilled.

Step 5: Drill Holes in Wood4

First picture:
   Drill holes in wood4 for the 3/8" diameter dowels (wood6) as indicated by the red marks.  The dowels should fit snugly.

Second picture:
   Drill pilot holes for the wood screws about 1" deep in each piece of wood4.  These holes should line up with the holes marked in red that were drilled in wood2 (step 3).

Any other holes in the picture do not need to be drilled.

Step 6: Drill Holes in Wood5

Drill holes in the centre of each block of wood5.  The dowels should fit the holes loosely.

Step 7: Drill Holes in Wood7

Drill a hole for a bolt through wood7.  Then drill 8 small holes for the photoresistor leads.  Make sure these holes can surround wood8.  These small holes are grouped 2 per photoresistor.  When you drill these holes, insert a photoresistor in each pair of holes.  You can use glue to secure the photoresistors.

Step 8: Attach Wood8

Glue wood8 to wood7 as shown in the picture.

Step 9: Screw Wood5 Into Wood3

Screw in a wood 5 piece at each end of wood3.  Use the 3/4" screws.

Step 10: Bolt Wood3 to the Solar Panel

Use 2 nuts and 2 bolts to attach wood3 to the solar panel.

Step 11: Attach Wood7

Push the bolt through wood7 and a solar panel mounting hole.  Thread on a nut and tighten.

Now check everything attached to the solar panel.  It should look like the 2nd picture (minus the wires).

Step 12: Wire Up the Photoresistors

Twist one of each of the photoresistor leads together as shown.  Twist long (approx. 18") wires to each of the remaining leads as shown.

Step 13: Screw Wood4 Into Wood2

Line up wood4 with wood2 as shown in the picture.  Screw the pieces together.  Repeat with the other piece of wood4 at the other end of wood2.

Step 14: Screw Wood2 Into Wood1

Line up the hole and screw together.  The base has been made.

Step 15: Attach Solar Panel Assembly to the Base

Line up the hole in wood5 to the hole in wood4.  Then push a dowel through.  The solar panel should be able to pivot freely.

Step 16: Attach Geared Motor to Base

I used a K'nex motor, so mine is different than the one in the parts list (in step 1).  You can probably figure out how to do this on your own (zip ties, perchance?)

Step 17: Attach the String to the Motor Shaft and Solar Panel

Tie a string through a mounting hole in the solar panel.  Tie the other end to the shaft of the motor and wrap it around.

Step 18: Screw in the H-bridge Motor Driver

Use 2 of the 3/4" long screws to attach the H-bridge to the base.  You may need to drill pilot holes.

Step 19: Build the Breadboard Circuit

Unzip the .zip file and there is a fritzing file of the schematic and breadboard view.  There are also jpg images of the schematic and breadboard views.  If you don't have fritzing, download it.  Be sure to use the male-to-female wire to connect the breadboard to the H-bridge.  Also, the geared motor that is attached to the base is called "pitch" in the schematic.  The motor of the rotating base is called "yaw".

Step 20: Screw Breaboard to Wood1

Make sure the solar panel can pivot about the dowels without hitting the breadboard.

Step 21: Place the Solar Panel Atop the Motorized Turntable

Simple as that.  Be sure you connect the wires from the turntable motor to the H-bridge.  The turntable motor is labeled "yaw" in the fritzing schematic (step 19).

Congratulations!  You have completed the project.  Send me a message on Instructables if you have any questions or suggestions.


giantpair (author)2016-01-04

I have everything except the LM324 op-amps. Could I use the LM741 op-amps instead and what coding should I change if necessary? THanks

laizo (author)2015-03-05

spencerearly (author)2013-09-15

Thanks. Did you build one and get it to work? I have always had trouble with the baseplate rotation and I took mine apart.


I built the circuit exactly as it was down on Fritzing, but it doesn't appear to operate correctly. Has anyone actually built this and gotten it to work?


Specifically, what is the problem? Is power appearing to be supplied?


Sorry for the delayed response. I had disassembled the circuit before you replied and I wanted to reassemble it before replying so I can be as detailed as possible.

I reassembled verifying and reverifying each placement in the board by removing each piece from the breadboard view as I physically placed it into my breadboard. I also double-checked by disabling the parts view and alternatively the wire view to verify that I placed everything in the right place.
When power is initially placed on the circuit, nothing noticeable takes place.
Pressing and holding the momentary switch activates the circuit with the following characteristics:

Even lighting on Up/Down Photoresistors= Up/Down Motor is still
Light on Up OR Down= Proper operation of Up/Down Motor
Even Lighting on Left/Right Photoresistors= Motor spins clockwise
Light on Left Photoresistors= Motor continues to spin clockwise
Light on Right Photoresistors= Motor Stops

Left/Right motor does not spin counter-clockwise under any test applied to my circuit.

Hopefully you can spot my mistake if I placed a part in the wrong location.

Also, What is the function of the momentary switch supposed to be exactly. I am not sure I understand the circuit that well to know what it is supposed to do.

Thank you for your assistance and time. I truely appreciate it.


The way you described the operation, there are no problems.

What you call the Left/Right motor, I will call the yaw motor. The term "Left/Right" motor is misleading because that motor can only turn in 1 direction. If you are in the Northern hemisphere, the yaw motor should only turn clockwise (looking down at the tracker). If you are in the Southern hemisphere, the yaw motor should only turn counter-clockwise. As long as the motors are rotating in the correct directions (given your description, and assuming you are in the Northern hemisphere, they do) there is no problem.

The circuit was not designed to allow the yaw motor to turn in both clockwise and counter-clockwise directions for simplicity's sake - the Sun will not unexpectedly change directions as it moves across the sky (hopefully). The disadvantage of this is that at the beginning of each day, you will probably have to manually turn the tracker to its initial position.

The purpose of the momentary switch is described in the "Parts list" in Step 1,

"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."

The circuit should make the motors move for a brief "burst" every several seconds. The button is there so you can press it without having to wait to see if the motors are moving in the right directions. Other than that, the button has no purpose and may be eliminated.

I hope that helps explain.


oh. I understand. I misunderstood its operation.

The design I am using this on has two motors that turn a threaded rod. Granted one of the axis will not move very often; however, I do want it to adjust to have the panels face the sun directly every time.

Its been a very long time since I was in electronics basics class, so I am quite clueless on the design of what I am looking for.

I can, however, follow a schematic. Do you think that it would be possible for you to modify this circuit design so that both axis respond to the light source? and if so, would it be possible to still use the same quad amp and motor driver?

I can't seem to find a design that will manage two axis anywhere online .

The closest I found was this one on YouTube:

The problem is that I don't want it to have a separate power source. That is redundant. I like that I can use the power from the panel/battery bank to supply the voltage needed for your circuit.

What do you suggest?


Interesting design from YouTube. I'm not quite sure how it works. I'll look into it and try to get back to you in a few days. It looks like they might be using some sort of a "centre tap" motors (motors with 3 terminals). Also, don't try building the circuit from YouTube unless you use flyback protection diodes for the relays (the schematic linked in the video description does not use flyback diodes). Otherwise, you may damage the op-amp. Use this circuit:

and connect the output of the op-amp to the open terminal of the resistor. The transistor (not included in the design from YouTube) amplifies the current from the op-amp to drive the relay.

I would recommend modifying my design over the YouTube design since I understand how mine works better.

Are you wanting the yaw motor to be able to rotate in both directions? If you want to modify my design to get that capability, you would need to have an additional op amp, requiring a total of 5 op amps (which would require another lm324 quad op amp chip). I'll post a picture of the modified (but untested) schematic in a few days, if you want.


I also have enough supplies. I ordered in bulk all of the parts you suggested


Yes. I want the yaw motor to go in both directions. The other main feature i like about your design is that it doesn't require a separate power supply to run the circuit

avelyn94 (author)2014-09-08

Does the tracker needed power to works?

spencerearly (author)avelyn942014-09-09

Yes. Look at the schematic( There is a power source labeled Vcc1 3V, but I used my 20V solar panel. I had to label it 3V because I couldn't find any 20V power source in Fritzing.

Also from step 1, "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."

Did I answer your question?

avelyn94 (author)spencerearly2014-09-09

yes. I had another question is what if the battery is out of juice will the tracker still be able to function?

spencerearly (author)avelyn942014-09-09

There is no battery. The tracker is powered by the solar panel (the same solar panel that is mounted on the tracker). Whenever the tracker moves, usable power output from the solar panel drops, so making the tracker battery powered might be a good idea.

avelyn94 (author)spencerearly2014-09-09

which mean if there is no sunlight available and the battery ran out of juice, the tracker will not be able to function when we required to tracker to track sunlight.

spencerearly (author)avelyn942014-09-09

If there is no sunlight, it doesn't matter if the tracker can function because you can't power anything with the solar panel in the dark

avelyn94 (author)spencerearly2014-09-09

erm.. for example there is sunlight on the right and the solar panel is facing to the left does that mean it will not be able to move because the battery is out of juice and its facing to no sunlight direction?

spencerearly (author)avelyn942014-09-10

If the sun is in the west, but the solar panel is facing east, all of the photoresistors will be in the shade and the direction the tracker should turn is ambiguous. Look at the picture:

The photoresistor on the left is in the shade. The circuit interprets this information and tells the tracker to rotate the solar panel (along with the photoresistor assembly) in such a way that all of the photoresistors are in direct sunlight.

In short, if the sun is not shining directly on the solar panel, the tracker doesn't know which way to turn since all photoresistors are in the shade. However, the diffuse sunlight should still be able to power the tracker.

gtoal (author)2014-06-19

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)gtoal2014-06-19

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 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!

hguzman3 (author)2013-11-24

Hi there, was wondering what was the wattage rating on the resistors that you used in this project. Thanks!

spencerearly (author)hguzman32013-12-20

I used 1/4 watt resistors. You should be fine as long as the wattage rating is at least 1/8 watt.

billgeo (author)2013-09-15

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...

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