<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; "><BR><DIV><DIV>On Apr 29, 2006, at 10:59 PM, John Luciani wrote:</DIV><BR class="Apple-interchange-newline"><BLOCKQUOTE type="cite"><P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">The regulator will handle the 15V on the input but it may not handle the power.</FONT></P> <P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">A 7805 in a TO-220 package (without a heatsink) should be able to dissipate</FONT></P> <P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">around 1-2 Watts. Since you have a 15V input the voltage drop across the</FONT></P> <P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">regulator will be 10V. Power dissipation of 1-2Watts would mean a maximum</FONT></P> <P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">output current of 100-200mA.</FONT></P> </BLOCKQUOTE></DIV><BR><DIV>According to Blacet's data sheet for his MIDI Sync PIC, it needs only 2mA to run (!!!). It can source up to 20mA at the outputs, but it's not likely that you'd really need to load your outputs that hard (unless you used them to directly drive LED's...). You'll also need a little current to operate the MIDI optoisolator chip (I don't know offhand how much -- keep in mind that the major current draw for a MIDI loop is on the MIDI Output side, not the Input side) My guess is that the whole shooting match is probably going to draw well under 50 mA through that 5 volt supply. The naked 78L05 attached to the 15 volt line should do just fine, I think.</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV></BODY></HTML>