Screaming_Rabbit Posted September 21, 2004 Report Share Posted September 21, 2004 Hello allI'll use the MEC switches for my MidiBox, with built in LEDs. http://www.mec.dk/files/LED%20tecinfo.pdfMy question to the electronic pros:Are the 220 Ohms resistors on the DOUT Board high enough or do I need further resistors before the LEDs?Greets and thanksRoger Quote Link to comment Share on other sites More sharing options...
illogik Posted September 21, 2004 Report Share Posted September 21, 2004 i'm no pro so i'm not sure but i think the 220R resistors will do just fine; it's just to lower the output voltage of the shift registers so it wont kill your leds. you could compare the data (Vmax) to the Vmax of a "regular" led cheers marcel Quote Link to comment Share on other sites More sharing options...
raphael Posted September 22, 2004 Report Share Posted September 22, 2004 Hello Roger,In short: 220R is just fine.I've found a interesting link for all the midibox users who are asking this question from time to time:http://www.theledlight.com/resistancecalculator.htmlJust enter the 'supply voltage' --> 5VThe LED forward voltage Vf (voltage drop) --> 2.1 V in your case (take the typical value)The LED forward current If --> 20 mA in your (and the most) casesYou will get 145R. So 220R is Ok (try a resistor with 200R or 180R for brighter LEDs but beware of overloading the outputs of the DOUT! 25mA is the maximum!).Easiest way: Do it with your calculator. The formula is:(Vbatt - Vf)/If = RSo: (5V-2.1V)/0,02A = 145 RHope this helps,Raphael Quote Link to comment Share on other sites More sharing options...
Screaming_Rabbit Posted September 22, 2004 Author Report Share Posted September 22, 2004 ... it does help :DThanks a lot Raphael!Greets, Roger Quote Link to comment Share on other sites More sharing options...
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