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View Full Version : Need help in connecting a super small lcd tv using power from PSU.


rafdmr24
10-07-2009, 04:41 AM
Hello all. I need an electric wizard's help.:) I want to connect this small Citizen Lcd Tv & Monitor using power from my pc's psu. It uses DC 9V.

Would it be possible to, say cut an unused molex connector & splice a plug or jack thingy on?

2 reasons i don't want & can't use the wall plug adapter,
1) I lost the adapter. (It got scrapped with my dad's Datsun 510)
2) It would be unsightly to have a cable running from the side on my open case.

Thanks for reading.:D
x88x
10-07-2009, 01:56 PM
What's the current requirement for the TV?
Airbozo
10-07-2009, 03:21 PM
What's the current requirement for the TV?

9 VDC... (in the original post)

I would think that you could easily modify one of the molex plugs for this, but you only have 12 VDC or 5 VDC.

You would have to put a resistor in line with the 12VDC line to drop it down to 9 VDC. I would also put an inline fuse just in case. But then again I am paranoid about that kind of stuff.
slaveofconvention
10-07-2009, 03:55 PM
Any idea what the current requirement of the monitor is in mA?
x88x
10-07-2009, 04:25 PM
9 VDC... (in the original post)

9V is the voltage requirement, but if it's not getting enough current it won't work, and too much current could easily fry it. Thus mine and slave's question.
crenn
10-08-2009, 05:40 AM
A beefy voltage regulator would work ;)
Airbozo
10-08-2009, 11:14 AM
9V is the voltage requirement, but if it's not getting enough current it won't work, and too much current could easily fry it. Thus mine and slave's question.

My screwup, I thought I was paying attention...
rafdmr24
10-08-2009, 11:48 AM
Hey guys, Thanks for the replies. I should have posted this in the 1st post, my apologies. It stated at the back of the lcd, DC9V - 4.5W. If thats what x88x & slaveofconvention was asking for? My apologies again if it isn't.
x88x
10-08-2009, 12:30 PM
O_o ouch. What's the current rating for the 12V rail on your computer PSU?
Luke122
10-08-2009, 06:12 PM
The conversion of Watts to Amps is governed by the equation Amps = Watts/Volts

For example 12 watts/12 volts = 1 amp

4.5/9v = .5 amps, or 500ma.

That seems kinda small to me.. how big is this television?
mtekk
10-08-2009, 07:06 PM
Ok, for the el-cheapo way of doing this, we'll use a linear voltage regulator. Looks like the L78S09CV will do ($0.89 at mouser (http://www.mouser.com/ProductDetail/STMicroelectronics/L78S09CV/?qs=sGAEpiMZZMug9GoBKXZ7578Qu64lAtCi0MdreJbuqF0%3d )). If you look at the part from the top (the metal tab is on the table and the pins are facing you) the connection order would be:
/````````````\
:``````O`````:
:,,,,,,,,,,,,,,,,,,,,:
|##########|
|##########|
|##########|
|##########|
|""""""""""""""""""""|
|.........|..........|
|.........|..........|
|.........|..........|
12V+ GND 9Vout

You'll need an .33uF capacitor to go from 12V to GND and a .1uF capacitor to go from 9Vout to ground. Should cost maybe $3 in parts.
x88x
10-08-2009, 09:44 PM
whoops, I saw 4.5A, not 4.5W :facepalm: ...that does seem pretty small.
rafdmr24
10-09-2009, 06:42 AM
@ x88x, is this it? +12v1 - 18.0A, +12v2 - 18.0A, +12v - 0.8A.

@Luke122, the whole unit is around 16 cm by 11.5 cm. The screen itself is around 7.5 cm by 5.5 cm. It's an lcd tv for vehicles.
x88x
10-09-2009, 08:32 AM
Yeah, that's what I was looking for. IIRC, the lowest current rail is your molex/SATA/etc connectors, so actually that works out really well. mtekk's got you what you need to do for the voltage, and I think the current should be close enough; your panel wants 500mA, and your PSU is supplying 800mA. I don't think that would be enough to kill the panel, but don't necessarily take my word for it ;)
slaveofconvention
10-09-2009, 12:43 PM
I think the third 12v is actually the -12v line so careful. Generally speaking, PC PSU's feed as much power as something draws, otherwise a single harddisk, for example, would be instantly fried if it was the only thing connected to an 18amp 12v line - there's should be ample excess power available thru one of the 12v rails tho - if you're close enough to your PSU's max to not have this much spare, you already need a new PSU anyway lol - oh and your computer would probably freeze regularly so almost certainly not an issue.
rafdmr24
10-09-2009, 04:15 PM
Alrighty .. thanks for the input guys & thanks for the link & the diagram mtekk. Really appreciate it. ;)
nevermind1534
10-09-2009, 07:30 PM
More amps or watts than something needs won't kill it. Too many volts, however can. This is why 1kW and 1.5kW PSUs don't kill people's computers.
Drum Thumper
10-09-2009, 08:08 PM
I hate to ask cause it'll make me sound like a dick, but did you google the model of the screen? I only ask because no one else has.
rafdmr24
10-10-2009, 05:33 PM
@Drumthumper, i did google it. Best link i found was from a russian? forum. Didn't have much info there.
Drum Thumper
10-10-2009, 07:08 PM
@Drumthumper, i did google it. Best link i found was from a russian? forum. Didn't have much info there.

Weird. With this being from a vehicle, I am a bit surprised that CarMP3.com didn't have any info on it.
rafdmr24
10-11-2009, 01:00 PM
Yeap, i was surprised as well. Probably it is too old?