power on atx psu#

a few methods to power on external disk and optical drive chassis

why#

atx power supplies wait for an external signal before they start delivering power. the intended use is that this will be provided by the motherboard. it can however be done manually.

this assumes the usage of a regular atx pc power supply. other power supplies should not be expected to behave the same way.

risks#

the basics to check. further details are beyond the scope of this guide.

• older power supplies expect a minimum load on certain voltage rails. when using such a psu make sure to always provide this base load.
• verify the supported load per cable & connector, factor in power spikes like multiple drives spinning up at the same time.

how#

make contact between ps_on (green wire) and ground (black wire) to signal the psu to power on. this contact needs to remain in place, if not the psu will power down.

option 1: paperclip#

a commonly used option is to use a paperclip to short ps_on to ground. while it does the job just fine there are a few things to take into account:

• can be fiddly to get it inserted, thin paperclips can fall out
• extended use can cause the contacts in the atx plug to wear out
• in general not advised to use unattended

option 2: atx plug with permanent connection#

does what the paperclip does but safer and more durable.

looks like this, pins tend to be very thin, perhaps to thin.

option 3: atx plug wired with switch#

seems like an elegant solution but it makes terrible contact so half of the time the psu won’t power on.

option 4: power converter board#

most expensive option relative to the rest, also does a lot more.

the idea is to use to power dedicated to the atx connector, in particular 5v & 12v, and reroute those to molex connectors to power more drives.

i did not take into account however that these are male connectors where i mostly need female ones. worries for later…

as soon as it detects any power, be it from plugging in the psu or some residual charge, the blue led will light up.

it also comes with a handy on/off switch.