USB Power?

Noobster · Post by **Noobster** » May 14th, 2006, 10:59 am

Hi, i'm just the average new guy who thinks that they have an idea. This has probably been done, so if it has could someone link me. What i'm thinking of is using the PC usb port (supplying 5 volts) instead of a pc molex connector. This could keep the lcd more portable. Again, if this has been done please don't flame me. Thanks

Post by **limbo** » May 14th, 2006, 11:52 am

this is possible...
depends on the desired current by the module.

In any case this must be done extremelly carefully!

fishthecat · Post by **fishthecat** » May 14th, 2006, 12:48 pm

I power my LCD using a USB lead, it works a treat.

_X7JAY7X_ · Post by **_X7JAY7X_** » May 15th, 2006, 12:55 am

I do the same, I actually use the USB power to power some of my electronic protoboards (VERY carefully). Most USB cords have a black (-) and red (+) in them. To be sure, I would skin these back and put a voltmeter on them.

J

Noobster · Post by **Noobster** » May 15th, 2006, 7:37 am

Okay, thanks for that. Its good to know that i'm not a lone ranger when it comes to this.

Post by **caesar** » May 15th, 2006, 7:55 am

I also use USB power! It is a normal process. I have read in some books on this subject that a USB device plugged should not use more than 100mA on powerup and not more than 500mA at any time. I suggest to use diodes for polarity and a fuse smaller than 500mA, remember that motherboards are expensive

fishthecat · Post by **fishthecat** » May 15th, 2006, 9:01 am

caesar wrote:I also use USB power! It is a normal process. I have read in some books on this subject that a USB device plugged should not use more than 100mA on powerup and not more than 500mA at any time. I suggest to use diodes for polarity and a fuse smaller than 500mA, remember that motherboards are expensive

Could you provide a circuit diagram.

Post by **caesar** » May 15th, 2006, 1:55 pm

Just did it...

Noobster · Post by **Noobster** » May 16th, 2006, 7:02 am

If you were worried about it drawing to much at system boot, couldn't you just add a switch so you had the choice of when to switch on? BTW, I have the most retarded power system for my board. I have a test PSU which powers 2 Hard Drives and a CD-ROM. Crazy huh.

Post by **caesar** » May 16th, 2006, 9:18 am

I wasn't reffering at system boot but at USB devices powering up, so basically if you have an LCD first it should start without backlight and after initializing the usb device (this cannot happen when just drawing power) only then to start using backlight. These are the USB specs.
I have found out that 350-400mA are no problem from the start in my case (I have a mouse and a USB->serial adapter that draw power, if any of you have other devices that draw more power from USB than don't use them all at the same time!) . If you want to be really sure use a self-powered USB hub...

LCD Smartie

USB Power?

USB Power?

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