By Murtaza Lukmanjee
We decided to implement the idea of having a solar tracker within some of the leaves of the RoboPlant in order to add to the Robotic effect of the plant and also to improve efficiency within the system. A solar tracker is a device which orientates a solar panel towards the direction of the sun in order to operate at maximum capacity.
Solar trackers are usually very expensive and do not come in required sizes that would fit onto a system like ours, hence having an off the shelf solar tracker had to be completely ruled out. After a few weeks of research we came out with various ideas to implement this feature within our plant. Some of the ideas of using a DC motor and a stepper motor are in one of our previous posts (please have a read).
The use of a DC motor and stepper motor resulted in having a few issues within our team. Firstly a stepper motor would have to have a gear box attached to it in order to provide enough torque to hold the leaf in place as we are looking at dimensions of about 0.5m x 0.5 m for the leaf which would include the weight of a solar panel which is around 2.5 kg. This didn’t seem to be too much of an issue as solutions were devised to overcome this and to connect the motors efficiently to the leaf (Also in previous post). One of the main issues was implementing a control system and the complex electronics behind such a model. This was far beyond our skill level and again would incur great costs as products from National Instruments don’t come cheap. Writing codes and setting correct parameters proved to be a tough task in such a short period of time.
With an idea given by Dr. Jose we decided on a very different approach. We decided to have a mini solar tracker completely separate from the RoboPlant which had a miniature replica of an exact cast of a leaf from the plant. We carried out some research and found a similar system that had work previously and are going ahead with giving that a try.
Material to be Used:
- Arduino MEGA 2560
- 2 GWS PARK HPX F Mini Servos (6v torque-3.6 kg.cm, 4.8v torque-3 kg.cm, weight-18g)
- Bread Board
- Jumper wires
- 5 LDRs
- 5 10k Resistors (depending on how it’s paired with the LDR)
This is the sort of system we are looking at. One servo would be mounted at the bottom which would rotate around the horizontal direction. Attached to servo 1 would be a mount which could be a piece of wood or a small structure of aluminium that allows for the connection of another servo rotating it in the vertical direction. Connected to servo 2 would be another small mount which the leaf is attached to. We are contemplating if we are going to have a solar panel mounted on the leaf or not.
Above shows the sort of arrangement of the different components that will be used for the solar tracker. An Arduino board is used in this system as it is cheap and easy to code. They are used for various small science projects which can be found online at different websites. The Arduino board is going to be connected to an external power supply of between 6V to 12V, it works best at this range of voltage especially around 9V as anything more than 12V could burn out the Arduino. It is coded with the use of a USB port connected to a computer and uses an open source software of its own which can be downloaded for free from its website. The two servos are connected to the arduino via the bread board using jumper wires. A set of 5 LDR (Light Dependent Resistors) are used which act as sensors in both the horizontal and vertical direction, hence placed as it is in the diagram. Each LDR would have a 10K resistor connected to it.
Circuitry wire set up tracker (Click to open)
The diagram and the file ‘circuitry wire set up tracker’ above shows the basic connection that needs to be made with regard to the wires, the colour coding and the pins it needs to be connected onto the Arduino board.
Pins 9 and 10 are used to connect the yellow wires off the servo.
Analogue input pins A4-A0 are used to connect the 5 LDRs and its resistors.
Both Ground pins are connected from the breadboard which are colours black and red. These lead to the black and red wire of the servo motors.
The coding for the Arduino is given is a separate sheet which will be used for this solar tracker. An Arduino shield could have also been used instead of the breadboard which would give you easy to access pins and would allow for an external power source of up to 12V, however we decided to keep it simple and just go ahead with the standard breadboard.
This is a fairly simple solar tracker with relatively cheap material. This miniature leaf would display the effect of phototropism which basically shows the plants response to external stimuli like the sun.
I will post up the completed circuitry, code and tracking system once complete, circuitry and system are subject to changes as we proceed through the building of this tracking system. Hope this was helpful and thank you for reading!
Reference for idea, circuitry etc: