A simple adjustable DC power supply: hardware

For more info, read about openbench

Outputs:

• 2 adjustable outputs
• 1 fixed output

Voltage:

• adjustable outputs: 0-30V, adjustable
• fixed output: 5V

Current:

• adjustable outputs: 0-2A, adjustable
• fixed output: 2A

Indication:

• voltage (for adjustable outputs only)
• current (for adjustable outputs only)
• current limiting active (constant voltage / constant current) (all outputs) (red LED)

Options:

• combine to 0-60V / 2A (series)
• combine to 0-30V / 4A (parallel)
• link voltages (can be used for parallel mode or symmetric output)

What happens when the power supply output voltage is set to 3.3 V, and I hook that output up to a 12 V battery? Which is better:

• The PSU pulls the voltage down to 3.3 V (or as close as possible until it hits the current limit)? or
• The PSU supplies zero current, letting the voltage float up to 12 V?

Should have a 3.3v fixed output as well as the 5v. Easy enough to handle. 1A should be good for most purposes on the fixed supplies. Elektor ran a switching PSU module in April that I made some tweeks on and currently as waiting on boards. Galvanically isolating the adjustible supplies is a potential issue. As soon as you hook a meter panel up, the two supplies are tied together. Hack around it by using two MCUs for A/D and transmitting to a third one via optoisolators?–pstemari

• "Bench power supply tutorial" https://www.adafruit.com/forums/viewtopic.php?f=8&t=24200
• "Bench-Top Power Supply" by James Littlejohn for the Tulsa Electronics Club
• "Building a digitally controlled bench power supply using an AVR" http://electronics.stackexchange.com/questions/18249/building-a-digitally-controlled-bench-power-supply-using-an-avr
• DIY Variable bench power supply http://www.instructables.com/id/DIY-Variable-bench-power-supply/
• DIY PSU into Bench Power supply http://www.instructables.com/id/DIY-PSU-into-Bench-Power-supply/
• DIY digital bench power supply http://hackaday.com/2011/06/06/diy-digital-bench-power-supply/
• My DIY Bench Power Supply http://www.swharden.com/blog/2012-12-18-my-diy-bench-power-supply/
• DIY Bench Power Supply http://www.adwiens.com/projects/electronics/07/index.html