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Old 05-20-2009, 12:02 PM   #16
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ok, so i figured out that i need a heatsink to dissipate 40watts because I'll be sending 32V, 2A (from the small solar panels) through a +5v 1A 7805. (so that link to the heatsink in my last post wouldn't work)

how would I search for a heatsink to dissipate 40 watts? i googled "TO-220 40w heatsink" but no luck)

if someone could please refer a link to a heatsink that would fill these requirements I would be greatful. i've been searching on google for 3 hours now and the more i look at, the more confusing it gets.


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Old 05-21-2009, 12:35 AM   #17
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Here's one that'll work. Go to www.mouser.com, and type 567-641-K in the Part Number search box. The one it brings up is a bit larger than needed (4.125"X3"), and it shows mounting holes drilled for a TO-3 device. The manufacturers specs state that this model has no holes. You'll need to drill one the same size as the hole in the mounting tab of the 7805. (The 641-A model has the TO-3 holes .)

567-120-SA is the heat transfer grease. All you do is smear a little dab on the back of the 7805 before you mount it to the heatsink. Enough to gush out the sides of the chip when it's fastened down. The excess is easily wiped away, or can be left on. It makes more heat transfer from the chip to the heatsink. If you don't use it, the chip will still work, but a reduced capacity.



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