| Project | Laboratory Power Supply |
| Date | 2006 - today |
| Goals | Create a multi-output variable power supply for my electronics lab |
| Dependencies | http://gcc.gnu.org http://avr-ada.sourceforge.net/ |
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 tune according to your lab's use. I needed one. It's also one of the thing most eletronics hobbist like to do. LPS will probably have the following specifications:
LPS will also feature: *Measure of output current and voltage *Recording of these measures over time *An isolated serial connection for a remote control and monitoring *Integrated PC switching supply
Architecture
In its heart, LPS has 3 Atmel ATmega16 microcontrollers that communicate with an I2C bus.
The power supply is provided by two toric transformers that deliver 80VA 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 13 volts and a second arround 26 volts. Both outputs are decoupled by 22000uF capacitors. 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 ATmega16 microcontroller to control two different power supplies. A first power supply controller is dedicated to the positive voltage, thus controlling the +0..20V outputs. A second one is dedicated to the negative supplies and controls the 0..-20V outputs. Because the ATmega16 does not have enough IO to connect the LCD, the serial line, control the power supply the output current, it was necessary to have a master board. The master board also contains an Atmel ATmega16 which communicates with the two power supply boards with the I2C serial bus. The LPS master directly connects to the 2x16 LCD controller.
Why so many microcontrollers? The Atmel ATmega16 is very very cheap. Instead of adding some control logic to have a single microcontroller drive the 4 power supplies, it was easier and appeared to be less expensive. It was also an interesting challenge to create such a distributed application.
Documentation
Project Planning
The LPS project is now managed using the free Online Project Management Service Planzone.