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Not another laptop LCD replacement question...

O

orangezero

Limp Gawd
Joined
Jan 4, 2003
Messages
211
I have a dell inspiron 1000 that was given to me because the screen was cracked. I've since removed it and use it with a regular monitor.

I also own a tm-868 8" lcd touchscreen and finally decided to try to put them together for use in my car. I realize there are sites on car computers, but no one is responding over there and this place gets 1000s more readers so I thought I'd try.

I was curious and got out a voltmeter on the power connector for the lcd of the laptop (that doesn't work). There are 5 or 6 wires and a ground. The voltmeter reads 18.76v steady on one them, 3.26 on the other one, most others are zero. The laptop uses a 19v adapter so I'm assuming its just running slightly low.

I was curious to see if anyone had tried to hook up another DC device to where the lcd used to connect to (I hope that makes sense). My lcd touchscreen is 12v / 0.8A. I was thinking I may be able to rig up a voltage regulator circuit and output 12v from the 18.76v??? I'm not sure how to check what draw the old dell lcd is capable of since its broken, but I would think it would be similar to the smaller touchscreen I'm adding and not be a problem.

IF this works, it means I have slightly less cabling and less chance for ground loop problems like using an inverter would cause. Not the end of the world otherwise. Is it worth trying?

All I've tried so far is using a power inverter in the car and using the two ac adapters (which equals pretty bad buzzing). I had also looked in to getting an igo universal adapter which allows dualpower but they seem to be of questionable reliability and the newer ones are super expensive.

thanks for reading and any replies.
 
I've done a bit more reading and perhaps I can make this a bit more concise.

Car battery fluctuates depending on what else is being used at the time. It appears my 18.76v going into the original broken lcd screen is rather well regulated and constant.

All I need is a circuit that will convert ~19v to constant 12v. I've looked at something like this:

http://www.elecfree.com/electronic/wp-content/uploads/2007/11/circuit_regulator_for_78xx.jpg

It appears I wouldn't need the rectifier since I'm already in DC. I'd probably need a small heatsink on the 7812 (12v) regulator, and just a few capacitors to get this to work?

Any thoughts?
 
I've read both posts and I'm still slightly confused. Are you just trying to power the new touchscreen via the laptop?

If this is the case, the laptop takes 19v at the jack and the lcd takes 12v. Tap in to the 19v at the dc jack (not the lcd cable) with a dc to dc converter and feed your touchscreen. If you google, you should be able to find a nice schematic along with a basic forumula for how to set input/output.
 
Just using the connector to power it, yes. I will be using the secondary monitor output to pass info to the touchscreen and not the original lcd connection. Sorry for the confusion.

I didn't really want to buy something expensive if I can use a $1.59 part and a few capacitors.
 
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