[hpsdr] Linear Power Unit (LPU)

[Scott Cowling]

Hi Lyle,

I thought about that, but this is actually a bit cheaper. Even with 
the resistor, I still need the heat sink (albeit perhaps a smaller one).

The TO-220 cased regulators and the large (but inexpensive) heat sink 
will handle the worst case dissipation of about 13.5W on the 5V 
regulator (9V at 1.5A). A 10W resistor costs about the same as the 
regulator IC (even though it is still pretty cheap)!

They would reduce coupling in noise from the station supply, though, 
so it might be worth it, and it would definitely help spread the heat 
around and put it into a part that can more easily withstand higher 
temperatures.

Maybe an option for the prototype? (Oh no, not more options!)

73,
Scotty WA2DFI


At 04:55 PM 10/30/2008 -0700, Lyle Johnson wrote:
>Hello Scotty!
>
>>Please take a look and comment. Keep in mind the goal of LPU:
>
>I like the idea a lot.  I wonder if some heat can be spread around 
>by putting a low ohm, high-wattage resistor in series with the 5V 
>and/or 3.3V regulators.  The input is going to be pretty tightly 
>regulated and won't go below 12V.  If we need to supply 1.5A from 
>the 5V reg and it needs 2V headroom, we could put a 3.3 ohm 10W 
>resistor in line. Similarly,the 3.3V 1A supply could use a 6.8 ohm 
>10W series resistor.
>
>73,
>
>Lyle KK7P