Now my Sensor has four eyes

Here is the 4-LDR version of the sun-tracking sensor with on-spot adjustment using four potentiometers. The four LDRs improves the field of view of sensor.  The micro-controller programming has been changed and tested under wide conditions of lighting and its working great.

So why i used the potentiometers? Because the all the 14 LDR's in my hand provided me different readings in dark and extreme light conditions. Only two LDR's matched together and for the rest i was getting the calculated resistors values 2.5K and 2.8K which are not standard values resistors. So i came up with potentiometers where i can adjust them to get the precise resistance. Now all the LDR's can be matched with these variable resistances and the sensor will give me perfect results. I will lock the pots once adjusted.

Now by change in microcontroller programming i shifted the timing interval control from the firmware to the hardware. Now the user can select the sense/react timing of the sensor with a single potentiometer and can change the movement of panels from real time up-to 15minuts delay. Real time means the panel sensor continuously track the sun and command the motor to move. I will set this for 10minutes for myself i.e. After each 10minutes the tracking sensor will start to move the panel toward the sun.

Why MPPT Charge controller?

Maximum Power Point Tracking gives  10-30% more energy from the solar panels. These controllers are connected between the solar panel and batteries like any charge controller, but sophisticated electronics allow the controller to operate the solar panel at its most efficient voltage, resulting in significant gains in power.

When 50 Watts isn't 50 Watts

 As an example, consider a 50-Watt panel. The panel will typically be rated for full output power only at a particular voltage, say 17V, at which it will produce a little less than 3 amps.

When you connect this panel to your batteries with a conventional charger, the panel will operate at the battery voltage, say 12.6V. At this voltage, the panel won't generate significantly more current than at 17V, and the total output will be less than 40 Watts!

MPPT controller will let the solar panel run at its most efficient voltage, extract the most power possible, and charge the batteries at their voltage, with almost no loss. This way, a 50 Watts power can be received from the 50 Watt panel, a 25% gain over the conventional controller in the example above!

MPPT controller extracts the most power possible from the panel in nearly any condition: hot or cold temperatures, different light levels, partially shaded panels; it even takes wiring losses into account. The actual power gain will vary with conditions, and may be anywhere from 0-40%, with 10-30% being typical. Highest power gains come with discharged batteries, cold temperatures, and lots of light. 

More accurate and Sensitive Suntracking Sensor

I have replaced the 10K resistors with more precise 3.2K resistors at the output of the LDR's  to analoge pins of microcontroller. These resistors are calculated for the available LDR's.

Following Formula was used:

LDR resistance(Ohms) = SQRT ( Rdark x Rnoon)

Where Rdark = Resistance of the LDR in night (No light condition) =247 Ohm

          Rnoon= Resistance of LDR at high noon (direct under the sunlight) =39000Ohm

LDR resistance = SQRT (247 x 39000)

                       = 3101 Ohm = 3.1 ohm

                       =3.2 is the nearest available resistance

Here is the spreadsheet version:

and a short video after 10K resistance replacement with 3.2K.

My Sun-tracker is Alive

Here is a short video of sun-tracker in working condition. It took my sunday to find out the weired behavior of sun-tracker. I found out two 10K resistors were the culprit on the PCB. I just removed them from the PCB and installed them directly on the sensor Analogue input wiring. My next goal is to make a pretty weather proof enclosure for the sun-tracker and electronics panel box.

My old video of sun-tracker testing:.

The latest video of my sun-tracker.

Calculating Energy efficient Tilt Angle for Solar Panel

As I have already discussed in the previous post that i am adding single axis tracking to my solar panel and the Altitude angle (Tilt angle) shall be adjusted in Summer and Winter to get the maximum efficiency out of the solar panels. Here are the Rule of thumb for best tilt angle.


 SEASON------------------- ANGLE TILT CALCULATION

Winter    --------------------  (Latitude x 0.89) + 24 degrees
Summer  -------------------  (Latitude x  1.05) - 24.3 degrees
Spring & falls --------------   (Latitude x0.98) - 2.3 degrees

Pakistan resides in Northern hemisphere so the Solar panel should be toward the TRUE NORTH. The Tilt angle is calculated from the Horizon.

Example:

City :  SADIQABAD, PAKISTAN
Latitude (from google) : 28.1700 N  
Tilt Angle for Winter= (28.17 x 0.89) +24 degree  = 49.07 
                               = Say 49 degree  from horizon or   (90- 49 = 41 degree) from the vertical
Tilt Angle for Summer= (28.17 x 1.05) -24.3 degree  = 5.27 
                                = Say 5 degree from horizon or (90-5 = 85 degree) from the vertical
Tilt Angle for Spring & Fall=  (28.17 x 0.98)-2.3 = 25.306
                                 =  Say 25 degree   from horizon or (90- 25 = 65 degree) from the vertical


As these solar panels i intend to install in Karachi so:

City :  KARACHI, PAKISTAN
Latitude (from google) : 24.8508 N  
Tilt Angle for Winter= (24.8508 x 0.89) +24 degree  = 46.11  = Say 46 degree  (90-46 = 44 degree )
Tilt Angle for Summer= (24.8508 x 1.05) -24.3 degree  = 1.79  = Say 1.8 degree (90-1.8=88.2 degree)
Tilt Angle for Spring & Fall=  (24.8508 x 0.98)-2.3 =  Say 23 degree

Testing the Solar Tracking module

Here is a brief video of solar tracking module.

Updates on Control module and Panel Support Structure

Micro-controller modules are completed .

Solar panel structure with single-axis sun tracker installed. I have used one Car windshield motor (Rs.700), motorcycle chain sprockets set (Rs. 450)  and a second-hand car wheel hub (Rs. 1600) to make a single axis tracking hardware.

 The structure material ,assembling and painting cost was around Rs.8000.

 I have also purchased 60V 10amp MPPT charge controller (Rs.8750), However, i am seeking to purchase 60Amp 160V MPPT charge controller (TS-MPPT-60 ) through credit card from America as its not available in Pakistan.http://www.morningstarcorp.com/en/tristar%20mppt It will cost me around 550 US dollars including taxes/duties.

purchased 02 Lead Acid batteries FB make 220AH. Cost me around Rs.24000. I preferred FB because the maintenance free deep cycle batteries are quite expensive and the market is full of poor quality Chinese batteries. Later on i shall discuss on this.

Why Single Axis Sun Tracking?

After successful completion of the DC Motor controller , it is time to make the Heart of the control circuit. I have recently completed the AVR based Single Axis microcontroller circuit for Azimuth tracking of the sun.

Using dual axis solar tracking is a good idea but controlling the Altitude motor with respect to sun has very little benefit as compare to Azimuth control.Let us see the following figures for explanation:

The position of the Sun in the sky relative to an observer on Earth is defined by its altitude angle α (solar elevation angle) and its azimuth angle Ψ. The sun moving from East to West and the this angle we call it Azimuth Angle. The sun daily cover this Azimuth Angle. However, The Altitude Angle of the sun is changes throughout the year with a very very little increments during the year days.In winter the sun is more toward the Southern side and Altitude angle is small . Whereas in the summer the Altitude angle is on the extreme and sun is just traveling at the top of our head;)..

 This is the reason I prefer to use Azimuth control of my solar panels.

Here is the micro-controller(ATMEGA328P) based single axis Azimuth control circuit with East-West limit switches. In future i shall explain how will this work.

Low Cost DIY DC Motor Controller for AZIMUTH Control

Recently i designed a low cost DC motor controller using relay, MOSFET IRL540N. This circuit can handle up to 5A current and i shall use this for AZIMUTH control of my Solar Panels. I shall use wind power shield motor to run on this circuit.

This circuit is under testing with micro-controller and doing fine so far.