Sometimes relays are used in power supplies to adjust the input power (select transformer taps) to the regulators so that the regulator doesn't have to dissipate too much power due to the difference between input voltage and output voltage. It will be interesting to see your schematic.
I left my schematic at school but tomorrow I can post a picture. But there is a input voltage (120V @ 60Hz) which goes through a step down transformer (17.5V AC) which then goes through a full wave rectifier. After that I designed my own voltage regulator circuit but for the voltage divider output I have three relays to select one of three resistors and/or pot. So the arduino biases one of three transistors on based on the one of three options picked (3.3, 5, or to 15) which then turns one of the three relays on therefore selecting an output voltage which is neatly displayed on a 16x2 LCD display which two momentary buttons for flipping through the options and selecting one of the outputs. I can post a picture of the schematic tomorrow there is one error in it that I haven't had time to redraw yet though.
Reading your comment wrong. The correct response would be a bench top lab power supply. Limited to 1.4A. It is actually what I am commenting with you on in my question about using the Mega328 standalone
If the relay was simply switching the relevant voltage, then you could just bring it to the front panel as a continuously available supply. That way you could use 3.3 and 5v simultaneously.
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