There are three SATA power connectors (white, 4-pin connectors with +5V, ground, ground, +12V) on the board, next to the SATA data connector.
How much current can be consumed by attached SATA hard drives in total, on both the +5 V rail and the +12 V rail?
I can state for certain that whatever the limit is, it is too low for my use case. But what is it exactly?
(My Odyssey can handle one external HDD just fine, but not two. After a while, the 12 V supply fails and delivers only 0,5 V, which (not surprisingly) means that the HDD will stop working.)
And in case someone think it is strange that I connect two drives: I have installed an M2-to-SATA expansion board, which allows me to connect more than one SATA drive at the same time, but the power connectors I mentioned above are all placed on the main board (not on the M2-to-SATA expansion board).
First of all, you can only connect a maximum of 2 HDDs to the board with a power supply of 12V/3A directly connected to the board. The included power supply in the box is 12V/2A. So, with that, you can only connect a maximum of 1 HDD. This is the limitation from the board. If you want to connect more than 2 HDDs to the ODYSSEY board, you need to power the HDDs separately. This is because the HDDs will not have enough power just by powering up the board using a 12V/3A power adapter.
You need a power supply like this to power the HDDs separately:
You need a power supply as above because HDDs need both 12V and 5V to function.
Also, you could use these cables to connect the HDDs to the above-mentioned power supply:
Hi. Thanks for the link. However, I was primarily asking about the capabilities of the Odyssey-internal DC/DC that outputs +12 VDC and +5 VDC on the SATA power connector.
Using a cheap computer power supply is a good idea (if I remember correctly, one of the pins in the “motherboard” connector needs to be grounded for the power supply to turn on - Just applying mains AC power will not start the different power rails).
But can I power up SATA HDDs from an external power supply, and keep them on all the time? If I perform a reboot of the Odyssey, do the SATA power nets need to go down in order for the HDD to reset properly?
You are right. It should be the PS_ON pin that needs to be grounded.
Regarding the HDD reset on SATA power, I will get back to you on the 7th of February because I need to consult about this with the team and we will be on Spring Festival vacation starting from today until the 6th of February.
Just in case someone reads this and decides to try it: Make sure to connect the ground net (GND, usually but not always a black cable) from external power supply to one or more ground pins in the SATA power connectors - Otherwise, in case of different output ground potentials (since the external PSU and Odyssey DC/DC parts are floating relative each other), all potential-equalizing currents will go through the SATA HDD data connector, which might disrupt the data transfer.