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A Modular PCB Layout
4) Regulated Power Supply
Submitted by krich on June 30, 2008 - 5:01pm.
Of course, the first module I built after completing the AVR Baseboard is a regulated power supply.
This module is a two quadrant module and can be connected to either side of the board. You have to be careful to rotate the module properly so that the power and ground matches up with the baseboard. A commercial product would probably have the connectors keyed, but I really didn't want to have to deal with that. I simply marked the board as being compatible with AB and CD and left it at that. Since this was my first module, honestly, I was having other, much larger, issues.
There is nothing spectacular about the circuitry. It is a standard 5V power supply, based loosely on the breadboard power supply tutorial at Sparkfun. It includes a on/off switch, a status LED for the 5V rail, a terminal block for easily connecting power, and a fuse on the 5V rail so that I don't blow up my electronics with a short. It's saved me at least once so far.
So now, with this module, I can power a 3.3V project or a 5V project with the same components. Maybe I should socket the Voltage Regulator with a female header receptacle. Then I can use the same board for any regulated voltage I want. Hmm...good idea...
Power Supply Module Schematic
Power Supply Layout
Finished Power Supply Module
Power Supply Module attached to Baseboard
Note: The addition of the screw terminals was something I added in after the board was already made. I simply coerced the 5mm spaced pins into the 1st and 3rd holes and jumpered the third hole to where it needed to go. Also, I omitted the reverse voltage diode because it wouldn't fit with the screw terminal in place. All things I plan on fixing in the next revision.