WebsterLeone
@WebsterLeone

Starting a thread for my digital modular audio system. Current work: the power supply. Takes one of three inputs, including a Dell laptop power adapter, a terminal block, or 5.5mm/2.1mm barrel jack.

In particular, I was trying to figure out a way to handle detecting if both connections on the terminal block are powered using only one input pin, which I first came up with something using an op-amp but it didn't handle detecting neither being powered. Then I realized that I could just put them at opposite ends of a resistor divider and if the resistor values are different, it'd give different values for which is on and which is off.

If both are on, you get the input voltage (assuming both are the same). If the first one is on but the second is off, you get roughly 3/4 the input voltage. If it's reversed, you get about 1/4 the voltage. If both are off you get zero volts. That output will then be fed into a voltage divider so the uC doesn't fizzle.


WebsterLeone
@WebsterLeone

I just freed up some pins on the microcontroller by moving some GPIO around. Anyway, the board is coming along nicely. slowly rearranging things to fit but may have to enlarge the PCB a little. I might be able to carve out a square with some creative placement to avoid it, but it's a 2-layer PCB, it wouldn't cost too much more to make it a little longer.

The board takes in 19.5 volts DC (ideally, up to maybe 24V if thermal budget allows) and puts out 18VDC and two 3.3VDC rails. 18V is just LDOs (2x), 3.3V is buck to 3.6V then LDO to 3.3V. Microcontroller is for shutting down rails when in standby and monitoring voltages, and is purely optional.


WebsterLeone
@WebsterLeone

I pulled the 3.3 volt converters off the board and made them standalone modules which makes them both easier and cheaper to test, as well as lets them be used in a breadboard (hence right-angle pins) or standalone. Vertical pins are for use as a module in a larger design, keyed by offsetting the in/out pins by half their pitch. This is basically done though I'm gonna make a few minor cleanup edits soon.

The PCB itself is 21mm x 54.5mm. I blame the weird size on the 0.1 inch pin spacing. Controlling dimensions are metric at least :V

Takes approximately 5V to 24V in, the SMPS drops it to about 3.6 volts, then the LDO brings it down to a fixed 3.3V to clean up the power further. The reason for a buck-converter into a LDO regulator is to cut down on electrical noise because it's for use in an audio system. This may or may not be overkill. 🤷‍♀️


WebsterLeone
@WebsterLeone

(Whoops, I split threads, see here for more info including the physical board: https://cohost.org/WebsterLeone/post/4699715-3-3v-regulator-compl)

I can include assemblies I made as components on another board. This will be useful to make sure I don't run into interference issues due to tall components on the main board of this power supply.


WebsterLeone
@WebsterLeone

I'm back to the power supply while waiting for parts for the audio card to show up. I decided to make a 12V module and the question is... do I make it have the same footprint as the 3.3V module?

Cons to making them the same:
‣ Can accidentally plug a 12V module into a 3.3V module and blow things up

Pros to making them the same:
‣ PCB reuse (could make same PCB for multiple voltages)
‣ Can become some sort of generic power supply module footprint that you can use for different projects with different voltages.

Another question: if I make them different, how do I do it. Currently leaning towards same pinout just shorter modules for higher voltages. 🤔

Opinions?


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