running motherboard off uncertain 12V supply

[metalphreak]

Back when your CPU had a small/passive/no heatsink due its low power consumption, most boards used the 5v or 3.3v rails. Newer PCs which require far more power use 12V and switching circuitry on the board to generate the required voltages so the current through the power wires is greatly reduced.

As for whether your board needs negative voltage, most if not all <5yro ones do not, but some older stuff does. Simply remove these wires from a normal PSU and see if it fires up

http://www.goodluckbuy.com/24pin-car-dc-dc-atx-mini-itx-pc-power-supply-12v-150w.html <--- this one lists current ability and also mentions +/-5% regulation on the 12v implying is does regulate the 12v input? Also specifically mentions its for Car use.

There's also wide voltage range input boards that look a lot more beefier ($50+ though):
http://www.goodluckbuy.com/160w-8v-28v-mini-itx-m2-car-pc-atx-psu-power-with-itps.html
http://www.goodluckbuy.com/210w-8v-28v-mini-itx-car-pc-atx-psu-power-with-itps.html
http://www.goodluckbuy.com/8-28v-160w-dc-dc-dc-atx-atx-itx-car-pc-power-supply-module.html
http://www.goodluckbuy.com/8-28v-200w-dc-dc-psu-itx-atx-dip-car-pc-power-supply-module.html

[Psi]

The current needed at -5V/-12V is probably pretty small.
You can get small dc/dc modules for $5-15 from digikey that have isolated outputs.
So producing -5V/-12V at low current from a positive supply is simple/cheap.

As for whether your board needs negative voltage, most if not all <5yro ones do not, but some older stuff does. Simply remove these wires from a normal PSU and see if it fires up

Yeah, i blew up one of the driver transistors on my 10year old diamond monster sound MX300 by doing that.
I think without the negative supply the driver switched hard on in one direction and overheated.
Fixed it though, new transistor and it was all good.

[benemorius]

Years ago I ran an athlon 1700 system in a car with the 12v rail unregulated. I was retiring it and I wanted to find out whether I had been going to a lot of trouble regulating the 12v rail for nothing. It was a short test since I still didn't really want to lose anything (it was not old hardware back then) but it did work. I think it even survived cranking voltage which was probably under 9v.

If I were you I'd give it a try. Everyone knows what the outcome will be if you go with a regulated solution, but there is something to be learned if you attempt it without regulation.

[NiHaoMike]

The current needed at -5V/-12V is probably pretty small.
You can get small dc/dc modules for $5-15 from digikey that have isolated outputs.
So producing -5V/-12V at low current from a positive supply is simple/cheap.

Even easier is to run a discrete charge pump from one of the main buck converters.

[Simon]

well I could regulate the panels down to say 12.5-13V with the battery in parallel and power the PC. Alternatively, charge the battery by day and run the pc off it by night, with the battery under load it will not be anything more than 12.5V

Or you could just power it from mains which will cost less than the battery.

My idea was to use it for Boinc crunching but make it eco friendly as I have the panels but not yet done anything with them

[Rufus]

Or you could just power it from mains which will cost less than the battery.

My idea was to use it for Boinc crunching but make it eco friendly as I have the panels but not yet done anything with them

How eco friendly is manufacturing a big lead acid battery which gets shipped halfway round the world and will be shipped back to some third world shithole for recycling in a couple of years when it is knackered?

[Rerouter]

alternativly you could abuse a charge controller, and just run the computer direcly off the panels and a large capacitor, when the voltage exceeds a level charge controller snaps on, and computer can power up, when it gets too low, you can make something to shut it down early, e.g. one shot comparitor, and just have the capacitors serve to smooth out things like planes and etc,

or if using one of those wide input supplies, you could probably run straight off the panels, and use a similar one shot comparitor thing to turn it on and off,

just thoughts that i myself have motioned through in the past

[mobbarley]

and just run the computer direcly off the panels and a large capacitor

Even several large 1F 12v capacitors for car audio would only buy you a couple of seconds before the voltage sagged.

[im_a_human]

I have an old PC I've setup. Now i put a laptop hard drive in it, so in effect there is nothing needing 12V - except for the motherboard that is putting it through a SMPS to power the CPU. So could run the motherboard off a non too strict 12V supply, like a car battery ?

I could be wrong but something like this might work...

http://uk.rs-online.com/web/p/linear-regulator/5455685/

[Simon]

Or you could just power it from mains which will cost less than the battery.

My idea was to use it for Boinc crunching but make it eco friendly as I have the panels but not yet done anything with them

How eco friendly is manufacturing a big lead acid battery which gets shipped halfway round the world and will be shipped back to some third world shithole for recycling in a couple of years when it is knackered?

but i already have the battery, would be a shame for it to sit there and go to waste

[Rufus]

but i already have the battery, would be a shame for it to sit there and go to waste

Then sell it to someone who can do something useful with it.

[Simon]

but i already have the battery, would be a shame for it to sit there and go to waste

Then sell it to someone who can do something useful with it.

i use it as a general battery to have handy. like when i need to run 12V devices when i'm away

[Rufus]

but i already have the battery, would be a shame for it to sit there and go to waste

Then sell it to someone who can do something useful with it.

i use it as a general battery to have handy. like when i need to run 12V devices when i'm away

And if you deep cycle it daily to run this thing it will be knackered in 18 months and you will have to buy a new one costing more than the mains electricity it saved.

[Simon]

this is getting booooorrring.

OK forget the battery, that is secondary, the PSU is more important. As I said previously the other option is to charge the battery by day and then use it by night

[Tooms]

I find the PicoPSU to be very good and i am in the process of building a home server setup where i am trying to get the complet watt very low and still have very good performance on the system.

Part1:  http://www.tooms.dk/Tblog/Showblog1.asp?BlogID=201110091828348325
Part2:  http://www.tooms.dk/Tblog/Showblog1.asp?BlogID=201110252324515723
Part3:  http://www.tooms.dk/Tblog/Showblog1.asp?BlogID=201111082030033196

Tooms