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FreeTrack Forum > FreeTrack : English Forum > Support : Tracking System > SFH485P in serie and USB Power question

RSS > SFH485P in serie and USB Power question

benmeijer	#1 16/10/2008 - 00h20 Top
Class : Habitué Posts : 208 Registered on : 19/07/2008 Off line	I ordered some leds (sfh485P) to build a new 3 point cap. I want to use 5v from the USB port of my PC. what is the best value for the resistor? When i use the Led assembly wizzard I use these values. V=5 v Vf=1.5 v If=50 mA result = 10 ohm 5v+ o-------\/\/\/\/------>\|-------->\|------->\|---------o - 1st Q: is this right? or should i use a value of 70 mA / 7.5 Ohm 2nd Q: is this save for the USB port of my PC
babasior	#2 16/10/2008 - 11h49 Top
Class : Webmaster (admin) Posts : 930 Registered on : 09/07/2007 Off line Www	WARNING : Use USB is dangerous, because if there is an error on your build your motherboard can be broken .... It's more usefull and safe, to use external power source ... Babasior. FreeTrack Online / www.Free-Track.net
eLeTrO	#3 18/11/2008 - 16h45 Top
Class : Apprenti Posts : 16 Registered on : 12/11/2008 Off line	Hello Babasior, What can be wrong in a simple build like this?? We have to use only the black and de red cables from usb, right?? It can damage anything? Thanx!
didja	#4 18/11/2008 - 20h30 Top
Class : Webmaster (admin) Posts : 1043 Registered on : 09/07/2007 Off line Www	From the Hardware FAQ : I want to use USB to power my LEDs. Attempting to use USB as a power source can permanently damage your motherboard if you're not careful, if you feel competent enough to use it, make sure you include a PTC fuse with a 0.2A current cutoff in your circuit as insurance.

FreeTrack Forum > FreeTrack : English Forum > Support : Tracking System > SFH485P in serie and USB Power question

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