634, PS/2 power source?

[SmashTheQUBE]

OK I have a Dell Inspiron 8200 laptop and I want to use the PS/2 port as my power source for the backlight and screen of my 634.

Is this a good idea or a bad one?

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[Patricksmalley1]

ummm it could turn horribly bad if you don't know what mA the PS\2 uses. typically the ps\2 port on a computer produces no where near enough amperes, i think around 15mA or so. the LCD, and that particular model needs about 600mA. although this is not your only option. you could check the paralell port for power. i know that it could put out a great deal, just don't do anything untill you have found out exactally which pin and how nuch voltage it puts out. Also be careful you might void a warrenty or two.

 

[SmashTheQUBE]

ummm it could turn horribly bad if you don't know what mA the PS\2 uses. typically the ps\2 port on a computer produces no where near enough amperes, i think around 15mA or so. the LCD, and that particular model needs about 600mA. although this is not your only option. you could check the paralell port for power. i know that it could put out a great deal, just don't do anything untill you have found out exactally which pin and how nuch voltage it puts out. Also be careful you might void a warrenty or two.

is 5V 200ma enough to power the LCD and backlight?

 

[Patricksmalley1]

nope, i have found out that the voltage and amperes that are given as operating are also the maximum. things fry if you go over them and they just don't work if you go under them.
the 634 actually needs 525mA to work, crystalfonts rounded up. anyway the datasheet has all of those goodies laid out.
http://www.crystalfontz.com/products/634/634full.pdf
By the way where are you getting 200mA from?

 

[SmashTheQUBE]

nope, i have found out that the voltage and amperes that are given as operating are also the maximum. things fry if you go over them and they just don't work if you go under them.
the 634 actually needs 525mA to work, crystalfonts rounded up. anyway the datasheet has all of those goodies laid out.
http://www.crystalfontz.com/products/634/634full.pdf
By the way where are you getting 200mA from?

oh I dug around in my closet and found a 5v 200ma adapter.

I'm checking Radio Shack's site for adapters, but they all seem to be either too little or too much.

Do you know what the maximum ma I can use on the 634 is?

 

[SmashTheQUBE]

Also I can only seem to find 4.5v adapters. That's close enough, would it still work or is 5v the minimum?

 

[Patricksmalley1]

it isn't enough. you could try the one in your closet. hey it's free and it won't damage your LCD(that is if you plug it in right). the one from your closet might not produce a lot of light compared to if you got a 600mA adapter. there is one thing that you must remember when using adapters power, if you go under what is required then it just won't turn on. if you go over in either the voltage or amperage then you risk frying someting.

 

[SmashTheQUBE]

it isn't enough. you could try the one in your closet. hey it's free and it won't damage your LCD(that is if you plug it in right). the one from your closet might not produce a lot of light compared to if you got a 600mA adapter. there is one thing that you must remember when using adapters power, if you go under what is required then it just won't turn on. if you go over in either the voltage or amperage then you risk frying someting.

that's good to know. my LCD is coming on Monday or Tuesday (hoepfully I'll be here for the FedEx person to sign) and I hope that the serial port will be enough to power the LCD itself and I can just have the backlight on when at home.

I'll post when it arrives and I get it all soldered up and I try it out.

Just so you guys now, I'm a software developer and I am planning to build software to run my LCD (because the CrystalFontz one doesn't download pages from the web, etc.) and I hope to have some feedback from everyone here on what to put in. Thanks!

 

[BenStein]

Backlight power by USB

Since I wanted my LCD to be entirely external (I bought a parallel LCD) I wired it so that it draws its power from the USB port. USB supplies +5v on pin 1 and ground is pin 4. So off the end of the parallel cable that plugs in at the PC, I have a short USB cable that plugs into the back of the PC to supply the LCD power.