What I wanted:
- 5V, 9V, 12V and adjustable power output
- 220V power socket
- power outputs on the front and also on the back for stuff that needs to be powered up all the time
- USB charging
- display voltage and current for each output
- ability to turn the display on/off for the outputs on the back – in case I want to see the current from the front panel outputs only
Started with a sheet metal box.
Designed the front and back layout. Already made a labeling mistake on the back.
Drilling openings…lots of them.
Modifying the buttons. Did not like the original yellowish mini bulbs. Replaced it with wide angle white LEDs that I could easily control with Arduino. Last picture – original on the left, modified on the right.
Printed front and back layouts on a white PVC self-adhesive laser printable sheet and stuck it on to the box. Still haven’t noticed the labeling error.
Shortening USB panel cables.
Somewhere in the middle of cabling…
That two small prototype boards with a little chip on them is a USB charge controller TPS2513 which allows to charge most of the devices at the full rate. Without it either the charging won’t start at all or the charging current is low.
All wired up
All power sources are MEAN WELL except for the one at the top which was ripped off a wall wart and is powering Arduinos and relays. Since 5V, 9V and 12V outputs have their own power supplies the ground is isolated between outputs. The variable power output (buck/boost converter) 0.8V – 32V is powered by 12V power supply and so it also shares ground with 12V output.
Now I noticed the labeling error. 5V and 12V labels are exchanged. Too late, who’s looking at the back anyway…
Used 2 Arduino Nano’s to read buttons, control button lights, control relays and sequence power on and power off (I did not want to turn all power supplies at once).
In stand-by, only one Arduino is powered up slowly brightening and dimming the power button waiting for a button press. After button is pressed (does not have to be the power one), the second Arduino powers up and starts turning relays on sequentially bringing power to each power supply.
If you are wondering about the voltage not being exactly 5.00V or 12.00V. The power supplies have adjustable voltage in the range of around 10% of nominal voltage. So why not set it exactly to 5.00V? USB specification for voltage is 5V +0.25V,-0.6V. A charger for one of my tablets outputs even more. Long cables cause voltage drop on the wires and that leads to a lower charging current. So there might be 5.00V on the power source output but there might only be 4.5V at the tablet usb port side (depending on the length and quality of the USB cable) and the tablet might even refuse to charge at such low voltage (which I’ve seen happening). Also most of the 5V chips tolerate up to 6V. The same reason for 9V and 12V, to compensate for voltage drop on the wires. And if I ever need 5.00V, I can always use the adjustable output.
Done and serving in a corner
Usual operation at the left, only 5V output at the back turned on keeping 2 mobiles and 2 tablets charged up. Picture on the right – when the power from the front panel is needed. The soldering station at the top is connected to power outlet on the back of the power hub.
Nobody has been killed or permanently harmed while building this, I was zapped by 230V only couple of times.