Solar panel driver – own construction

The solar panel driver uses five modules:

• main board
• power supply module
• bus
• X axis controller
• Y axis controller
• multi module that supports:
  • display HD44780
  • keyboard PS/2
  • X axis sun sensors
  • Y axis sun sensors
  • anemometer sensor
  • real-time clock (RTC)
  • additional outputs (to be used in the future)
  • you can use ethernet module

Each module is controlled by processor Atmega32 or Atmega8.

Main board:
Main board contains processor Atmega32 (SMD). It is simple and cannot have elements that could indirectly or directly affect the transfer of data to the rest of the modules. It cannot include any systems that intermediate in communication, which in case of failure (dampness) may make any additional disturbance or unspecified states, thus causing failure of the rest of the modules or cause self-diagnosis or lack of reading the fault code. It measures the voltage at the accumulator, therefore it has a reference voltage source.

Bus module:
The communication rail does not contain electronic systems. It is a simple connector between all of the modules. It is a laminate connecting each pin in a row with each next pin in the next row, as it is done on cd-rom tapes. Plugs have 40 pins each. For this bus, like the tape, you can attach any number of systems.

X axis controller module:
The X axis controller is a powerful servo controller based on transistors IRFZ44N and IRL2910SPBF. These are MOSFET transistors with high current efficiency. The reason why they were used in this project is that you can power a lot more powerful engines with it. It is controlled by the processor Atmega8 in housing QFP32, through opto-isolation SFH6916 it controls the PNP and NPN transistors which drive IRF and IRL.
Circuit protection, for example, if the mechanism freeze in the winter, are not controlled from the processor. In case of excessive current consumption, engines are switched off anda message about the situation is sent to the main board of the processor. The processor gives the message to the other systems, so error message is displayed. In case of burnout or break of the connection with the engine at the module startup (first move since the network failure), the code of the failure will be saved and displayed. But how can the controller know that the wires were broken?
Current measurement is one of the solutions and the other is feedback signals. If the phototransistors placed on the photovoltaic panel do not change their values as intended, it means that the mechanism is blocked.
There is also a feedback signal in the form of pulses sent to the engine through the opto-isolation, however, it is used for the self-diagnostis of the control module. There is also DS18B20, which sends the temperature of the IRF and by 1-wire it transmitts the temperature not to the driver (Atmega), but to the main board, which in case of overheating turns off the current flowing to the control transistors or reduce the amount of control pulses sent to the driver.

Y axis controller module:
It is similar to X axis controller module. Communication is done through the same pins, temperature measurement is also via 1-wire, because the bus supports a lot of devices of different addresses on one pin.

Multi module:
Multi module consists of a display based on standard HD44780 (4x20 characters, which is enough for implementation of basic settings in a clear way and checking the error codes or actuators tests. What more, it displays the position of the panel or state of accumulation charge, date, time. RTC has programmed permanently leap years. It also has a battery backup which lasts for a month of work at low temperatures. The battery is also charged in real time. One of the main goals of this driver is its resistance to interferences, such as cars, lightning, fog lights placed on houses and other light sources that could attract the attention of C phototransistors. Therefore, the RTC plays the key role. If the Sun after the sunrise goes behind thick clouds, the panel must move on the track of the day before or another previous sunny day.
Phototransistors have a very linear characteristic. Minimal resistance got by lighting the phototransistor with a 100W light bulb was 6ohm, and the largest was 140Mohm. Lenses are so positioned, so that its useful resistance occurs when lit by the Sun while the light reflected or from behind the clouds is ignored.
The control module has also a microcontroller, which after checking all the devices on the board turns on the X and Y axis controllers, then controls the current flowing through the relays and in case of a breakdown, it cuts off the broken axis. Of course, it happens only when the thermal and short protection in each axis fails. It also has a beeper indicating a short as in each axis with a red LED (so you know where is the short circuit) and reset button, which allows you to restart the device after changing the broken module.

Pictures:





Link to original thread (useful attachment) – Sterownik panelu słonecznego