VACS:Projects:Hardware:LPS:MasterBoard
| Status | |
|---|---|
| Schema finished | |
| Validated the schema | |
| Validated the board layout | |
| Board manufactured | |
| Board finished | |
| Board tested | |
Contents |
Description
The master controller drives the two power supply controllers and manages the user interface as well as the remote interface.
Mains Supply Sensor
The mains supply sensor is intended to detect when the LPS mains is shutdown. When the mains is shutdown the master controller can ask the power supply controllers to shutdown smoothly the power supplies.
Temperature Sensor
The master controller measures the temperature of the heatsink with an LM35. The sensor generates a
Fan Controller
The master controller can control two fans. The fan is powered by the +5V and -5V, hence creating a 10V supply for the fan. The fan is enabled by a PNP transistor that drives the +5V supply. The fan rotation sense output is an open collector connected to the -5V. To protect the ATmega16 input, two resistors of the same value are used to generate a 0V signal (one connected to the fan open collector output and another to the +5V supply). The sense fan output is used to measure the fan speed.
PC Supply Power On
To power on a PC ATX power supply it is necessary to tie the ATX enable line to the ATX ground. We could do this with a simple open collector logical output but this would connect the PC ATX power supply to the LPS ground. To isolate the ATX power supply from LPS we use a relay that will connect the ATX enable. The relay is driven in the same way as the fan: with a PNP transistor connected to the +5V supply and the relay connected to the -5V supply.
Communication
RS232 Interface
The LPS master controller has an RS232 interface that can be connected to a host computer for monitoring and controlling the LPS outputs remotely. The RS232 connection is isolated so that the LPS outputs are not connected to the earth through the RS232 and PC connection.
I2C Interface
The I2C interface is used by the master controller to communicate with the power supply controllers. The master controller initiates the communication while the power supply controllers behave as slaves. The I2C interface uses the SDA and SCL lines. The pullup resistor is integrated in the ATmel microcontroller.
SPI Remote Programming
The master controller can use the SPI channel to program the power supply controllers. The SPI channel contains the MOSI, MISO and SCK lines which can be connected to one of the power supply controller or disconnected (in which case it is used to communicate with the LCD display). The master controller also controls the reset line of the power supply controllers. This is necessary for the synchronization and to enable the remote programming mode of the ATmega16.
The MOSI, MISO and SCK lines of the master controller are connected to a 4053 CMOS switch to select one of the two supply controllers. By default the switch is disabled so that the SPI channel can be used to control the LCD display.
LCD Panel
The LCD panel contains the LCD display, two pulse generation wheels and five buttons. It is connected to the master controller through a 12 pin ribbon cable. The LCD display uses a SPI-based interface that is connected to the MOSI, MISO and SCK lines of the master controller. Because the SPI is also used for the remote programmation, the LCD chip select must be driven low so that the SPI interface is taken into account by the LCD display.
The LCD panel produces two separate analog voltage for the buttons and for the wheels. The voltage is different for every combination of the buttons and every rotation of the wheels. The two analog voltages are measured and the value determines the appropriate combination.
Datasheets
Below is a collection of datasheets, white papers and articles related to the parts used in the board.
Resistors
Capacitors
- [SOLID POLYMER ALUMINUM CAPACITOR CHIPS IN DC-DC CONVERTER MODULES REDUCE COST AND SIZE AND IMPROVE HIGH-FREQUENCY PERFORMANCE ]
- [CONDUCTIVE POLYMER ALUMINUM SOLID ELECTROLYTIC CAPACITORS ]
- [Electrolytic Capacitor Guide ]
Relays
- [Omron Relay ]
