On Wed, Sep 5, 2012 at 8:25 PM, James Newton wro= te: > I have a pin coming out of a chip that indicates an error condition. Pin > will be at +5 or ground. (e.g. not a 3.3 volt system) > > The output requires at least 4.7K ohms resistance, or risk pulling more t= han > the iMAX rated current for that pin. > > PCB already done, no room for a transistor to amplify the output (next > revision). > > So the question is this: What LED would you use to get the most noticeabl= e > indication from 5 volts through a 4K7? > > I'm thinking very small, but diffuse red. > > But then I notice the ones with the highest mcd rating are always clear..= .. > > Any experienced advice? You don't mention the voltage drop of the LED. Are you calculating 4.7K ohms as 4700 =3D 5 volts / Imax ? Or are you just assuming a red LED which fixes the Vdrop? --=20 Martin K. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .