Yeah, I know it's an odd question, but hopefully I can explain it well. I'm looking to power up and power down a motherboard without shutting down the PSU. Here's what I have in mind. In my new system, I will be expanding and using some of Langer's ideas regarding a pico-itx board for system control. It's something I wanted to do with the Rogue, but just didn't take the time for. However, here, it will be a priority. I will have a pico-itx system connected to a touchscreen, aquaero, and multiswitch. The aquaero will be responsible for total system control. It will run the fans, pump, monitor temps and flow, as well as turning the main system on and off. Naturally, this will require more power than a typical pico PSU can provide, not to mention that I want to keep it down to one power cord. Now, I have my main PSU that I want to use to power all of this. I don't care of the PSU is on all the time, but I want to be able to power down the main system without shutting off the PSU (which will still be providing power to the pico, aquaero, fans, pump, and touchscreen.) So, I'm not sure if creative use of relays or the multiswitch can accomplish this. One thing to keep in mind, is that the pico-itx uses a standard 12 volt power connection meant to be plugged into an external power brick. It will be getting that power directly from the main PSU instead, so 24 pin splitters aren't an option. So, what do you think my options are? Any ideas?
That would be the easy answer, but not practical in this case. I simply don't have the room to give up. So, that's left me to come up with a complex solution for a simple requirement.
Would it be possible to make a link between the motherboard plug and the pico system. Using the pins used for jump starting the PSU, would you not be able to basically have a wire link to a power switch for the pico system. Switch could be replaced with something else that was i could think of just now. Chris
The green wire needs to be grounded to simulate being plugged into the MB - like a bench test PSU. But... You want to interrupt the circuit between the PSU and the mother board allowing one MB to shut down(the main system) while still powering the PICO? Interesting. I'm thinking aloud here. john
Where's cpemma? This could probably be done with a single switch called a make before break. Make the ground connection to the case before breaking the circuit to the main MB. Green wire is grounded, first so PSU stays on and main MB gets no power signal for MB ready and shuts off. That may be too simple. john john
I haven't tried, but tapping into the green wire with a switch shorting to ground, would allow the psu to stay on, so everything is still recieving power, until this ground/psu switch is turned off. The mobo would still turn off the hdd's, etc, and be shudown, but everything is still recieving power at thier rails. I expect that actual power use would be very little during this shutdown but psu is still on state, as in less power use than standby mode. A diode could also be chucked in between the mobo and the tapped point of the green wire for protection, but i dunno if the mobo would even need that? We'd have to analyse the mobo circuit diagram for that so lets just use a diode
how does a motherboard turn the PSU on? if the PSU detects current drawn on the green wire, then i dunno what to do. but if the motherboard closes a circuit and returns some current back to the motherboard, this should be fairly easy to do. just intercept the current before it gets back to the PSU, and instead direct it to a relay which closes a switch on each wire going to a component on the main PC. then have a separate switch to just turn the PSU on and off.
Thanks for the input so far guys. So, the green wire is key. If I tap into it to power the pico on and off, then the main system becomes less of an issue. I could use the aqua computer multiswitch to power up the main rig. I could then power down as long as the signal on the green wire stays. I may not be explaining it clearly, but I think I have the idea...
It has been my experience that the act of just grounding the green wire with any of the black wires turns on must PSUs. However it should be noted that most PSUs need some sort of a current draw - a fan etc. to run reliably. I use an old HDD as the current draw. A fan might be enough. The Pico board is well within what what would be a power drain.
Excellent artistic representation mvagusta! You're right John, I've heard that some current draw is needed, and I'll certainly have it here. I think I have the info I need to continue. I think I was over thinking it. I appreciate the help!
Yeah i know, it's the same top secret cutting edge software i use to make motivational posters. Is there nothing it won't do? +1 make sure you have a few watts of load on each of the 3 main rails, (12, 5 + 3.3), such as pumps, fans, etc when manually operating a psu. Oh, and with that diagram, the mobo would turn off together with the mobo on shutdown, when switch A is in the off/normal operation posistion.
Why not use a small 1U PSU in the 150-200W neighborhood? They are small, and make the solution simple.
Another PSU simply isn't an option. This question is related to the OSIDIAS project linked in my sig. Here are the internals...
Presumably what you want is the PSU and ITX board working as normal and then a "fake" PSU which you plug all your wires into and turns off and on like a regular PSU but without all the bloated power converters: It looks more complicated but AFAIK it's much "safer" and gives you much more control over what turns on (providing you implement this).
