VACS:Projects:Software:LPS
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| − | In its heart, LPS will probably have 3 to 4 Atmel | + | In its heart, LPS will probably have 3 to 4 [http://en.wikipedia.org/wiki/Atmel_AVR Atmel ATmega8] microcontrollers that communicate with an I2C bus. |
The power supply is provided by two toric transformers that deliver 50VA on 2x9V. One transformer is dedicated to the positive supply while the second one to the negative supply. A rectifier board is associated with each transformer and it delivers two outputs one arround 11 volts and a second arround 22 volts. Both outputs are decoupled by a 22000uF capacitor. The rectifier board also contains a set of relays and current sense resistors to measure and limit the current. The board directly delivers the power to the power supply transistors which are mounted on a huge heater. To control the power supply a specific board uses an Atmel ATmega8 microcontroller to control two different power supplies. One of the two is a fixed voltage and the second one is variable with the voltage controlled by the microcontroller. A first power supply controller is dedicated to the positive voltage, thus controlling the +0..18V output and the fixed +5V. A second one is dedicated to the negative supplies and controls the 0..-18V output and the fixed -12V. Because the ATmega8 does not have enough IO to connect the LCD, the [http://en.wikipedia.org/wiki/USB USB] module, control the power supply (8-bit [http://en.wikipedia.org/wiki/Digital-to-analog_converter DAC]), the output current, it was necessary to have a master board. The master board also contains an Atmel ATmega8 which communicates with the two power supply boards with the [http://en.wikipedia.org/wiki/I2C I2C] serial bus. The LPS master directly connects to the 2x16 LCD controller and to an USB module. | The power supply is provided by two toric transformers that deliver 50VA on 2x9V. One transformer is dedicated to the positive supply while the second one to the negative supply. A rectifier board is associated with each transformer and it delivers two outputs one arround 11 volts and a second arround 22 volts. Both outputs are decoupled by a 22000uF capacitor. The rectifier board also contains a set of relays and current sense resistors to measure and limit the current. The board directly delivers the power to the power supply transistors which are mounted on a huge heater. To control the power supply a specific board uses an Atmel ATmega8 microcontroller to control two different power supplies. One of the two is a fixed voltage and the second one is variable with the voltage controlled by the microcontroller. A first power supply controller is dedicated to the positive voltage, thus controlling the +0..18V output and the fixed +5V. A second one is dedicated to the negative supplies and controls the 0..-18V output and the fixed -12V. Because the ATmega8 does not have enough IO to connect the LCD, the [http://en.wikipedia.org/wiki/USB USB] module, control the power supply (8-bit [http://en.wikipedia.org/wiki/Digital-to-analog_converter DAC]), the output current, it was necessary to have a master board. The master board also contains an Atmel ATmega8 which communicates with the two power supply boards with the [http://en.wikipedia.org/wiki/I2C I2C] serial bus. The LPS master directly connects to the 2x16 LCD controller and to an USB module. | ||
Revision as of 18:31, 9 September 2006
| Project | Laboratory Power Supply |
| Date | 2006 - today |
| Goals | Create a multi-output variable power supply for my electronics lab |
| Dependencies |
Contents |
Overview
I started LPS during the 2006 summer althought I had this idea for a long time. Every electronics lab should have some power supply that you can adjust and use. I needed one and it's also one of the thing most eletronics hobbiest like to do. LPS will probably have the following specifications:
- 0..18V/2A
- A positive variable power supply with a full voltage scale digitally controlled (8-bit resolution). The output current is measured and is also limitted.
- +12V/2A
- A fixed 12V output with a maximum 2A load. The output current is also measured and limitted.
- +5V/2A
- A fixed 5V output with a maximum 2A load. Likewise.
- -12V/2A
- A fixed -12V output with a maximum 2A load. Likewise.
- 0..-18V/2A
- A negative variable power supply.
LPS will also feature:
- Measure of output current and voltage
- Recording of these measure over time
- An USB connection for a remote control and monitoring
Architecture
In its heart, LPS will probably have 3 to 4 Atmel ATmega8 microcontrollers that communicate with an I2C bus.
The power supply is provided by two toric transformers that deliver 50VA on 2x9V. One transformer is dedicated to the positive supply while the second one to the negative supply. A rectifier board is associated with each transformer and it delivers two outputs one arround 11 volts and a second arround 22 volts. Both outputs are decoupled by a 22000uF capacitor. The rectifier board also contains a set of relays and current sense resistors to measure and limit the current. The board directly delivers the power to the power supply transistors which are mounted on a huge heater. To control the power supply a specific board uses an Atmel ATmega8 microcontroller to control two different power supplies. One of the two is a fixed voltage and the second one is variable with the voltage controlled by the microcontroller. A first power supply controller is dedicated to the positive voltage, thus controlling the +0..18V output and the fixed +5V. A second one is dedicated to the negative supplies and controls the 0..-18V output and the fixed -12V. Because the ATmega8 does not have enough IO to connect the LCD, the USB module, control the power supply (8-bit DAC), the output current, it was necessary to have a master board. The master board also contains an Atmel ATmega8 which communicates with the two power supply boards with the I2C serial bus. The LPS master directly connects to the 2x16 LCD controller and to an USB module.
Why so many microcontrollers? The Atmel ATmega8 is very very cheap. Instead of adding some control logic to have a single microcontroller drive the 4 to 6 power supplies, it was easier and appeared to be less expensive.
