Psu powered monitor?

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travalon

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Oct 18, 2009
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Hi all,
I'm really glad everyone is here to let me know if my ideas are as good as I think.

So, I bought this AOC monitor ( http://www.newegg.com/Product/Product.aspx?Item=N82E16824160060 ) $100 shipped to go with this build.

i3 2100
MB ASROCK|H67M-ITX/HT H67 LGA1155 R
VGA PNY|VCGGT4301XPB GT430 R
MEM 4Gx2|G.SKILL F3-10666CL9D-8GBXL
Seagate hybrid 500gb 7200 rpm x 2
A little old Coolmaster case w/300 psu
a dl dvd multi writer from a laptop stuck in a usb enclosure
and a Thermaltake Slim X3 cpu heat sink and fan

I know my psu is severely lacking and will probably be getting a 450 watt soon.

Now my idea... The monitor has an external converter. 12 volts 3 amps, and runs around 25 watts when not in eco mode. I would like to tap into the 12v rail of my soon to be PSU to power the monitor. Everything will be going into a custom built case. It will be similar in design to a desktop replacement, and i would like to have only 1 power cord.

What do you think? Can/should it be done?

Thx

 
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One advantage would possibly be a "cleanera' and better regulated +12 V.

How I'd go about doing it.
1) use a male molex adaptor. Can use one of of the short adaptor cable that plugs in to the Molex connectors. Cut the end off, and splice two wires.
.. black pin for return and Orange wire for the +12 V (NOTE the red wire is for +5 V)
2) need a female power connector (from Radio shack). Use one of the blanks covering a unsused PCI slot on the back. drill a hole to match the Power connector. Route the wires from the molex to the female power connector.
3) Buy a male power connector to plug into the female connector. Build a cable to go between Back of PC -> monitor, Recommend you use an inline fuse (4 or 5 Amp) for the +12V Out line. Reason the brick will act to limit the make current to the monitor - The +12 V PSU rail may allow 20+ amps to the monitor!!!
4) Put a Power plug on the other end that will plug into monitor. OBSERVE polarity (measure with a DVM (Don't have - get one from walmart, about $15 - Don't know how to use - They are so simple a cave man can use, just google "How to use a voltmeter).

For wire, I'd probably use 20 ga. (22 ga would be OK).

Added: really want to be safe, add a diode in line so that current will only flow if polarity is correct. Inline on Black wire - The line Or arrow) toward the computer.
 
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Wow Chief you joined TH the same year I was born.

Now I'm not sure. There are multiple wires coming out of the psu.

Sata power
molex power
24 pin power
4/6/8 pin power

So which one should I use I always have extra cables/wires that aren't attached to anything.
Also you are thinking just like I would do it Chief only with more wisdom. I hadn't thought of a fuse or a diode.

Radio shack here I come.... (sometime in the next few days)

Thx
 
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Get your power from the Molex (Has 4 wires to connector. One end Red = 5 V, two center wires black = return (Gnd), and at other end a Orange (or yellow) wire that is your +12V.

Did NOT join in 1970. When Tom's made a change all cuurent members had the Join date reset to Jan 1 1970. I probably joined around 199x.
 
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^ Brett, you say this because??

He clearly stated that the monitor was approx 3 amps (36 watts), then molex connector connected to a rail is normally (he does need to verify) is 20 AMPS. If he places a 4 or 5 amp fuse inline as I suggested current would max out at 60 Watts (5 amps @ 12V).
 
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Hi :)

Although I appreciate your point, because "I" understand the difference between Amperage and Voltage and Ohms law...

I suspect that the OP doesnt...and anyone who starts playing with electrics that does not understand them is an accident waiting to happen...or an electrocution waiting to happen....

All the best Brett :)

 
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Brett,

Learn or burn.


You are assuming I am incapable of finding the information needed to do this safely and without toasting my monitor. So, instead of putting me off, I appreciate your concern, would you mind giving me your honest opinion of how you would do this if it was your idea? I am hoping to get many more opinions and Ideas from multiple members so I can decide if It can be done safely. and if so what would be the best way.

I just ordered this PSU

CORSAIR Builder Series CX430 V2 (CMPSU-430CXV2) 430W ATX12V v2.3 80 PLUS Certified Active PFC Power Supply

28 amps on the 12v rail

$20 @ tigerdirect

Thx
 
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While it looks good, a couple of points to consider.
1) would connect to the 5 V rail so instead of 3 Amps directly off the +12 V PSU rail you would connect to the +5 PSU rail and current would be 7.2 Amps (if 100% eff which say 80% = 8.6 Amps). The 5 Amp rail is generally more limited on available power.
2) Since this must convert the 5 Volts to 12 V, Not sure what the output would look like, ie Noise/ripple. As load increases the noise and ripple would increase. It would need some filter caps on the output.

Basically, just adds a circuit that is not needed since the PSU has the +12 V directly. And the added circuit adds one more failure point.

Ref the Diode I added. This is a great Idea for reverse polarity protection, But ther is one problem ( slipped my feeble mind). The Diode forward biased voltage drop will be close to 0.5 V. If PSU has a 12.0 V output the available voltage at the monitor would be 11.5 V. This would probably be OK, However; The +12 V from the PSU has a min spec of 11.4 V. If your PSU hade a Output of 11.7 V (In spec) the voltage at the monitor would then only be 11.2 V.
Based on this, I'd omit my diode and Just insure the polarity is correct. Si diode forward drop is 0.5 V, But a Ge Diode it is only 0.3 Volt - But Ge Diodes are normally signal diode and have low current capabilities. (NOTE: Si = Silicon, Ge = Germanium)
There is a alternate whay than that is to put the diode in parallel (across the Red/black wires) between Fuse and monitor. Arrow points toward the Red wire. If you revearsed the Wires (hard to do as black wire goes to Black!!) this would then "pop" the Fuse. Note FORCING the molex on backwards would still have gnd to gnd, But output would be +5, not +12. Just remember YOUR red wire goes to the Orange (or yellow) wire not the red wire.

Brett, "or an electrocution waiting to happen", Have never heard of someone being electrocuted by 12 V. A 12 Volt car battery can supply several hundred amps and you can stick you fingers acoss the terminals and never Know it.

The only real hazzard is if he has a short between the fuse and molex connector +12 V which would allow 20 Amps to flow and the PSU would shut down. This possibility would be alievated by simply measureing the resistance at the +12 V at the connector that plugs into the Monitor to chassie ground, Molex plug disconnected, should be greater than 20 meg ohms. Then connect the molex connector and measure the voltage at the Monitor plug end for +12 V to verify both voltage and POLARITY.
 
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Use one of these mounted to an expansion slot cover plate with a hole drilled out to fit the barrel power connector:

http://www.e-itx.com/cab-pwr-m4-b2p.html

You need to ensure (i.e. rewire if necessary) that the barrel power connector has the correct polarity for the center pin.


Use a DC Power Plug 5.5x2.1mm Male Extension Connector Cable of the appropriate length to connect up the monitor like the following:

http://www.dhgate.com/dc-power-plug-5-5x2-1mm-male-extension-connector/p-ff8080813184cbb8013192c92b1e1118.html

The monitor itself will have its own circuit board with its own voltage regulation and filtering since the logic chips will require much less than +12V for their operation.
 
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thx Chief I admit I'm not as educated as you about these things and when I found this I was thinking it might work but there was something that made me wonder. Still not sure what it was but your "And the added circuit adds one more failure point. " is enough for me to nix it. Il\'ll keep looking but I think simpler is better in this case.
 
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That's amazing!!! The molex plug is the first thing to pop into my head after my idea and Chief validated it. And now you find me the piece.
I never thought the monitor would have its own circuit board w/ voltage regulator. A simple call to AOC should give me the info I need. (just to confirm your info - Safety first!!! - wouldn't want to electrocute myself to death;p)

I still think Chief's suggestion of an inline fuse would only add extra protection to the monitor. I'll ask tech what the max amps the monitor can handle then pull as much off that for a fuse. I was thinking 3.5 amps.
Oddly enough I think I have all the parts here already Sans fuse.

Simple seems to be better if it works.

Had to RMA my mobo now I've got something t work on.
 
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