Messages in this thread | | | Date | Wed, 30 Jul 2003 21:02:41 +0200 | From | Pavel Machek <> | Subject | Re: PATCH : LEDs - possibly the most pointless kernel subsystem ever |
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Hi!
> > My construction of LED lights is extremely flaky, and I'm afraid of > > burning printer port. At 486 days ports were expected to survive such > > abuse. Not sure if todays EPP/wtf ports can handle that. > > parport uses 5V (actually a little less) so if you > use normal (not extra super duper bright) leds and > put a 1kOhm resistor in front of each led, then it > will drain 5mA per led, which gives a total of 40mA > for eight leds (for example) > > now for the parport: depending on the technology > and the age of the circuit, it provides between > 2 and 14mA output at >2.4V (the led usually requires > less than 1.5V to operate) so this would be within > the range ... but, if you want either extra brightness > or extra security, you could provide +5V and use > the outputlines as sink, which then is between > 15 and 25mA ... > > anyway, parport should be short circuit safe, so > the worst what could happen is, that the leds are > not working ;) ...
Really? Even for newer designs? I was afraid not to kill southbridge...
> PS: I usually use 220Ohm and no external power ...
I used 330Ohm and no external power. 8leds were bright (those on data pins), 4 dim (those on control pins). That was 486, through.
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