[time-nuts] Adding adjustment pot to 5680

[Arthur Dent]

>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
++++++++++++++++++++++++++
I had considered mounting the 7805 on the vertical heatsink you see 
to the left of the 7805 in my photo, using a short screws in either side 
of the the tapped hole that is already there and use leads to connect 
the 7805 to the connector pins, but felt it wasn't necessary. Directly 
connecting the regulator to the DB-9 pins was much simpler. 

FYI, the load is not 100Ma as you assumed, that is the max rating of 
the 78L05 that I didn't use. The actual load the 7805 sees in the 5680A 
is about 80Ma so even at the higher temperatures inside the case I 
don't see a problem.  You are correct that it might be a better practice 
to mount the regulator on the heat sink, especially if this were a 
production item, but in this case I felt it was overkill.
http://farm8.staticflickr.com/7013/6668466093_90782cf7e9_b.jpg


-Arthur