Hi all,
Long story short my embedded computer motherboard that only runs off of 12v doesn't have enough power to run the number of SATA drives/devices I want to. Or at least not comfortably safely for me. My goal is 4x 2.5" drives which on average pull 1-2A on 5V on boot. Ideally, the motherboard mfgr will get back to me with the max current I can pull from the 5V rail from the onboard SATA power connecter/DC distribution board BUT if they don't or it is to small I'm looking at alternate options.
Right now this is my plan:
12V into the case -> Split -> 1/2 to the motherboard & 2/2 to a picoPSU where I can hook up the SATA drives. The kicker is I want the SATA drives to power down when the board goes to sleep or is off as it will spend over 95% of the time in sleep mode -- no reason to wear and tear the drives.
What I want to do is take the 5v rail from the onboard SATA connector run it through an optoisolator and have it switch the ATX 'soft power' pin on the picoPSU. So once SATA power comes on the optoisolator acts as a tiny relay and brings the picoPSU up and when SATA power goes off it brings the picoPSU down too. That will ensure the SATA drives are ready for the rest of the computer when needed and there isn't a timing delay with either the detection circuit or method and are also off in lock step when they aren't needed. It seems relatively elegant.
My question is do I need anything more in my circuit to make this happen? On the SATA side it needs to run the optoisolator LED so I assume a small current limiting resistor is a good idea? I'm also planning to run on HDD on the SATA line directly to make sure enough current is being used. On the picoPSU side all the testers are just a wire jumper shorted 100% so I can't imagine I need anything on that side?
But I'm curious what others think? Honestly, it seems to simple and elegant to be safe and correct. So I'm asking here.
I haven't taped into SATA power before and really don't want to fry the one power connector on my board or even worse -- the entire board and embedded processor with it.
Long story short my embedded computer motherboard that only runs off of 12v doesn't have enough power to run the number of SATA drives/devices I want to. Or at least not comfortably safely for me. My goal is 4x 2.5" drives which on average pull 1-2A on 5V on boot. Ideally, the motherboard mfgr will get back to me with the max current I can pull from the 5V rail from the onboard SATA power connecter/DC distribution board BUT if they don't or it is to small I'm looking at alternate options.
Right now this is my plan:
12V into the case -> Split -> 1/2 to the motherboard & 2/2 to a picoPSU where I can hook up the SATA drives. The kicker is I want the SATA drives to power down when the board goes to sleep or is off as it will spend over 95% of the time in sleep mode -- no reason to wear and tear the drives.
What I want to do is take the 5v rail from the onboard SATA connector run it through an optoisolator and have it switch the ATX 'soft power' pin on the picoPSU. So once SATA power comes on the optoisolator acts as a tiny relay and brings the picoPSU up and when SATA power goes off it brings the picoPSU down too. That will ensure the SATA drives are ready for the rest of the computer when needed and there isn't a timing delay with either the detection circuit or method and are also off in lock step when they aren't needed. It seems relatively elegant.
My question is do I need anything more in my circuit to make this happen? On the SATA side it needs to run the optoisolator LED so I assume a small current limiting resistor is a good idea? I'm also planning to run on HDD on the SATA line directly to make sure enough current is being used. On the picoPSU side all the testers are just a wire jumper shorted 100% so I can't imagine I need anything on that side?
But I'm curious what others think? Honestly, it seems to simple and elegant to be safe and correct. So I'm asking here.
I haven't taped into SATA power before and really don't want to fry the one power connector on my board or even worse -- the entire board and embedded processor with it.