Hey guys, new to arduino. Got inspired to design a ITX Pc Case with moving vents.
Is there any way to connect the arduino to the PC mother board for power and run the servos when the PC turns on or off?
Any tips are much appreciated!
Your PC power supply has a 5V rail and you can access it through a sata drive power adapter.
| 1 | +3.3VDC | 3.3 V Power | orange |
|---|---|---|---|
| 2 | +3.3VDC | 3.3 V Power | orange |
| 3 | +3.3VDC | Enter/exit Power Disable (PWDIS) mode | orange |
| 4 | GND | Ground | black |
| 5 | GND | Ground | black |
| 6 | GND | Ground | black |
| 7 | +5VDC | 5 V Power, Pre-charge | red |
| 8 | +5VDC | 5 V Power | red |
| 9 | +5VDC | 5 V Power | red |
| 10 | GND | Ground | black |
| 11 | Optional | Staggered spinup/activity | black |
| 12 | GND | Ground | black |
| 13 | +12VDC | 12 V Power, Pre-charge | yellow |
| 14 | +12VDC | 12 V Power | yellow |
| 15 | +12VDC | 12 V Power | yellow |
Don't think you can do much with it when the PC shuts down unless you warn the Arduino through software and have it complete its actions before the PSU shuts down.
Unless you add a battery which might not be the best idea.
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Welcome
I don't think the 5VSB is enough to safely power the arduino and a few small servos, so I think the most reliable way is to have an external power supply.
If you can open the PC's PSU for modifications, you can solder the AC input of the external PSU to the AC input of the PC's PSU (after the power switch, if there is one) so that you don't need 2 power cords. Then using a DC current sensor module on a 12V (for example) output of the PC's PSU so the arduino can detect when the PC is turned on or off
Is there a way to warn the Arduino before the PSU shuts off? Saw some suggestions that using a super capacitor might help to move the servos to a close position is the power shuts off... will look into that if possible
That is a possibility!, but will have to factor in extra space for a second PSU. I was trying to go for a ITX and compact build. So initially preferred a method through software alone or less meddling with the PSU.
Well now, the PC shuts off when you command it to, and it takes some time to do so, neatly closing processes and open disk files.
It should be possible to arrange a process which is called promptly on the command to close down and sends a signal to the USB serial port to which the Arduino is connected.
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Perhaps it would be best for the Arduino to be powered by + 5VSB and the start and stop button of the computer to be connected only to the Arduino. In this way, the Arduino (for example via an optocoupler) will control the start and stop of the computer. If this is possible, no additional power supply will be needed because the motors will only run when the main power supply is switched on at full power and the Arduino will be powered continuously from the + 5VSB line.
Hack a central heating zone valve , when powered they open , when power removed they close with a spring .
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But I would imagine most of us do not use the "start and stop button" to shut down the computer.
I use it to put the computer to sleep so that when I want to use it, it starts (almost) immediately. 
What do others do?
This seems to be quite useful in detecting shutdown (on windows).
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