[sdiy] Quick voltage regulator question

[Michael Bacich]

On Apr 29, 2006, at 10:59 PM, John Luciani wrote:

> The regulator will handle the 15V on the input but it may not  
> handle the power.
> A 7805 in a TO-220 package (without a heatsink) should be able to  
> dissipate
> around 1-2 Watts. Since you have a 15V input the voltage drop  
> across the
> regulator will be 10V. Power dissipation of 1-2Watts would mean a  
> maximum
> output current of 100-200mA.

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.


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