Dual Axis Solar Tracker Sensor

If anybody could help me I would greatly appreciate it:

I have a class project where me and my partner are building a dual axis solar tracker with the following materials:

two servo motors for horizontal and vertical movement.
four photoresistors to detect light intensity and to move the panel to the highest source of light.

Here is where we need help:

My professor keeps telling us we need to use sensors to tell us the change of voltage or current as the panel rotates to determine if we are receiving a good amount of voltage/current. Can anybody tell us what sensors we can use for this? Our professor is not really helpful at all. Can't we just connect a voltmeter to the panel to display voltage? Is that what he means?

Any help would be greatly appreciated. Thanks.

jm1009:
If anybody could help me I would greatly appreciate it:

I have a class project where me and my partner are building a dual axis solar tracker with the following materials:

two servo motors for horizontal and vertical movement.
four photoresistors to detect light intensity and to move the panel to the highest source of light.

Here is where we need help:

My professor keeps telling us we need to use sensors to tell us the change of voltage or current as the panel rotates to determine if we are receiving a good amount of voltage/current. Can anybody tell us what sensors we can use for this? Our professor is not really helpful at all. Can't we just connect a voltmeter to the panel to display voltage? Is that what he means?

Any help would be greatly appreciated. Thanks.

What voltage? Show us a drawing of the circuit you are considering.

Since this is an Arduino forum, are you also considering using one in the project? If so, what part might it play?

Have you decided what type photo resistors you will use?

Paul

Google “arduino dual axis solar tracker” for thousands of similar projects.

Like this one, one of the first I ever saw.

Hi,
Welcome to the Forum.

As you will find in the examples previously posted, your professor wants you to use the LDRs, photo-resistors to sense the output of the sun and point the panels in the optimum direction for maximum power output.

You cannot use the PV output as its voltage will vary not just on solar radiation, but your load that you will have connected to the PV.

Can you tell us your electronics, programming, Arduino, hardware experience?

What subject is this project being set for?

Thanks… Tom. :slight_smile:

Paul_KD7HB:
What voltage? Show us a drawing of the circuit you are considering.

Since this is an Arduino forum, are you also considering using one in the project? If so, what part might it play?

Have you decided what type photo resistors you will use?

Paul


Here is the circuit we are considering doing provided by BrownDogGadgets. And the Arduino UNO will be used. A sensor shield will be connected to it, and the two servo motors will be connected to it as well as the four photoresistors.

& according to our professor, he is referring to the voltage that the panel receives from the light source. He keeps mentioning a "voltage sensor or current sensor" to determine whether or not the voltage we are receiving is good or not. But me and my partner don't know what exactly the professor means. Please provide any help you can. Thanks!

TomGeorge:
Hi,
Welcome to the Forum.

As you will find in the examples previously posted, your professor wants you to use the LDRs, photo-resistors to sense the output of the sun and point the panels in the optimum direction for maximum power output.

You cannot use the PV output as its voltage will vary not just on solar radiation, but your load that you will have connected to the PV.

Can you tell us your electronics, programming, Arduino, hardware experience?

What subject is this project being set for?

Thanks.. Tom. :slight_smile:

Thanks Tom! Yes, we know that the four LDRs are necessary to sense the output of the sun to move the panel to the optimum direction. However, he keeps mentioning a voltage or current sensor that we need to use, but me and my partner don't quite understand. As far as electronics goes, we are sophomore college engineering students. We know DC circuits and AC circuits, transformers, transistors, inductors, capacitors, etc. Programming wise, we are good at some C++, Python, and Linux. Hardware and Arduino wise we are pretty good. The project is basically done - EXCEPT for the fact that the professor WANTS us to include a voltage or current sensor, but for what? I need some clarification. Any help will help us. Thanks in advance!

EXCEPT for the fact that the professor WANTS us to include a voltage or current sensor, but for what?

Ask the professor.

However, a clever person might guess that the professor wants you to demonstrate that the power output of a solar panel is maximum when the panel faces toward the sun.

It is a bad idea to power the servos form the arduino.
You might get away with that with a single servo, unloaded.
2 is really pushing it, and as soon as you put a load on the servos, they will draw more current that the 5v pin can provide and at best, reset the arduino. You might damage the arduino.

MUCH better to have the servos powered from an independent source.
I attached an example.
ServoDiagram.jpg

ServoDiagram.jpg

vinceherman:
It is a bad idea to power the servos form the arduino.
You might get away with that with a single servo, unloaded.
2 is really pushing it, and as soon as you put a load on the servos, they will draw more current that the 5v pin can provide and at best, reset the arduino. You might damage the arduino.

MUCH better to have the servos powered from an independent source.
I attached an example.
ServoDiagram.jpg

Thanks for the feedback. My partner and I will supply power to the two servo motors with an external power supply.

Im still confused though. Essentially, my professor clarified to me that he wants us to incorporate a voltage sensor which is basically a voltage divider circuit, which surprises me since do we even need it?

Well, it’s always good to check the output of the solar panel. Voltage is one measure.

Hi,

Im still confused though. Essentially, my professor clarified to me that he wants us to incorporate a voltage sensor which is basically a voltage divider circuit, which surprises me since do we even need it?

I would say your professor is trying to get you to provide measurment of panel output power for Proof Of Concept report.
You do a couple of days or lab simulation with tracking OFF.
The the same with tracking ON.
Or comparing to a static array of PV.

What are the specs of you PV array, total power, open circuit volts, short circuit current, this will dictate the type of current shunt.

You are now at a level of education where you will find you need to show how your experiment or project performs and in this case the increased efficiency of tracking.

Thanks.. Tom.. :slight_smile:

TomGeorge:
Hi,I would say your professor is trying to get you to provide measurment of panel output power for Proof Of Concept report.
You do a couple of days or lab simulation with tracking OFF.
The the same with tracking ON.
Or comparing to a static array of PV.

What are the specs of you PV array, total power, open circuit volts, short circuit current, this will dictate the type of current shunt.

You are now at a level of education where you will find you need to show how your experiment or project performs and in this case the increased efficiency of tracking.

Thanks.. Tom.. :slight_smile:

Our PV array has specs of 5.5 V, 330 mA. We're planning to connect a voltmeter LCD to the panel so we can see how much voltage the panel reads when the photoresistors point to the strongest source of light.

You'll need to measure the current, too.

Hi,
With that low level of PV voltage and current, you will need to make a current shunt and amplifier to give any decent current readings.

To read current you will need to run the current through a shunt resistor and measure the voltdrop across it.
The volt drop at the low level of current and your PV voltage will need to be very low, in the mV range.
You will need to amplify it to get good resolution out of the 5V/1024 count Arduino AtoD.

Also you will need to present a schematic of your project, I don't think your professor will accept a Fitzy picture.

It about time you started to show us a schematic.

Tom... :slight_smile:

TomGeorge:
Hi,
With that low level of PV voltage and current, you will need to make a current shunt and amplifier to give any decent current readings.

To read current you will need to run the current through a shunt resistor and measure the voltdrop across it.
The volt drop at the low level of current and your PV voltage will need to be very low, in the mV range.
You will need to amplify it to get good resolution out of the 5V/1024 count Arduino AtoD.

Also you will need to present a schematic of your project, I don't think your professor will accept a Fitzy picture.

It about time you started to show us a schematic.

Tom... :slight_smile:

Our professor said the voltage sensor (voltage readings of the panel) is fine and that we do not need to show current. Just one or the other.

We will also present a schematic. The professor wants every detail of the project, which he will receive, it's just that he sometimes confuses all of us in a way that we need to seek help from other sources.

Our plan currently is to run the voltage through a voltage divider (per request of our professor) and to connect an LED voltmeter in series to the panel to display voltage from the panel. We know the current is small, however this is merely a prototype.

If anybody else has any suggestions it would be greatly appreciated.

P.S: The motors, the bluetooth, and other components that do not need to be powered by the arduino will be powered by a secondary power supply.

jremington:
You'll need to measure the current, too.

As jm1009 said, you don't need to measure the current. Why would you? When would the optimal voltage position not be the overall optimal position of the panel?

Did you ever finish your project? Any video? Code?

I've seen many projects using a DIY sensor similar to the one in the video that CrossRoads posted (for your convenience, here: http://www.instructables.com/id/Arduino-Solar-Tracker/ )

If I get it right, the sensor takes an average of LDR1 and LDR2 (my image, upper setup), which will be used in the calculations. And an average of 3 and 4. Further it needs an average of LDR1 and LDR3, and an average of LDR2 and LDR4. Having two LDR's to get one value might give you precision, but is it overkilling?

My approach would be like in the lower setup. LDR1 and LDR2 would work as a voltage divider. One analog input (A0) would get the reading. This reading would tell how to adjust the vertical position. 2.5 V should be optimal. A similar setup for LDR3 and LDR4 and another analog input.

One single reading from one analog input would tell how to adjust in one dimension, instead of calculating averages.

From one datasheet of an LDR I read that the resistance of the LDR (in concern) varies from 400 ohm to 1 Mohm. Connecting two LDR's as a voltage divider would make 800 ohm at its least. If that is critical (it would make a 6.25 mA current), one would have to add a 500-1000 ohm resistor in series with each LDR. if 2 Mohm is too much (full darkness) to create a voltage division (which would make the analog input port float), one would have to add a 10-50 Kohm resistor parallel to each LDR.

As jm1009 said, you don’t need to measure the current. Why would you? When would the optimal voltage position not be the overall optimal position of the panel?

You measure the current because current is proportional to light intensity.

PV panels are current sources. The open circuit voltage does not depend in a useful way on light intensity.

However, when the solar panel is properly loaded with a resistive load, then the voltage across the load is also a measure of light intensity and power generated

I read from a datasheet of a 12 V panel that its nominal voltage is 12 V, its maximum power is 60 W, its maximum voltage at maximum power is 17.2 V and current is 3.49 A. Does this mean that 12 V is kind of an average? And the panel just gives some current at some voltage at some amount of sunlight? And at say 50% sunlight (that is 50% of the maximum) the panel would give some maximum current at some voltage? And at that 50% sunlight, if there's no load, the measured voltage would probably be much higher?

One would think that there still could be some characteristics of the panel that tell the ratio or something similar between the amount of sunlight, the current load and the voltage. These characteristics would of course vary from panel model to panel model.

Johan_Ha:
I read from a datasheet of a 12 V panel that its nominal voltage is 12 V, its maximum power is 60 W, its maximum voltage at maximum power is 17.2 V and current is 3.49 A. Does this mean that 12 V is kind of an average? And the panel just gives some current at some voltage at some amount of sunlight? And at say 50% sunlight (that is 50% of the maximum) the panel would give some maximum current at some voltage? And at that 50% sunlight, if there's no load, the measured voltage would probably be much higher?

One would think that there still could be some characteristics of the panel that tell the ratio or something similar between the amount of sunlight, the current load and the voltage. These characteristics would of course vary from panel model to panel model.

Sorry but it sounds like you have not done a lot of research into how PV panels work and how to use them.
Just reading PV panel data sheets is not the full story.

Please read.

Look at the I-V curve.
Tom.... :slight_smile: