On Mon, 9 Jan 2012 13:06:12 -0800 (PST) Arthur Dent <[email protected]> wrote:
> On the inside of the case where the DB-9 > pins go through the circuit board, I mounted a 7805 fixed regulator. I > cut a piece out of pin 4 and connected the output of the 7805 to the > board side of the pin with a tantalum cap for bypass. I decided not to > use a 78L05 because at the elevated temperature I felt it would be > cutting it too close to the 100MA current limit. [...] > http://farm8.staticflickr.com/7013/6668466093_90782cf7e9_b.jpg You are driving the 7805 near its limit. As a rule of thumb, a TO-220 case can disipate about 1W of power, if it's free-standing. You have max 100mA with a voltage difference of 10V, resulting in 1W max. Ie the 7805 will be running at a considerable high temperature. As you have there a good heat sink already (the case), i'd mount the 7805 against the case and use wires to connect it. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
