7815 heatsink

[9 volts]

Hey there, I have a 7815 regulator (15v) getting 24 volts(1 amp), and using a brass pole as a heat sink. This is getting really hot. Is a bigger heat sink the answer? 24 volts falls within the regulators range. Thanks

[9 volts]

sorry 7915

[jakenold]

The 7915 is for negative supply! Get a 7815 for this application.

Jake

[9 volts]

The 24 volts is dc

[9 volts]

ok.......a quick check. It's a 7815, so my measurement of 24 dc is incorrect also. (whoops). I'll recheck for the correct input (ac) voltage. Thanks, sorry about the confused info.

[miqbal]

LM7815
1 Ampere POSITIVE voltage regulator
maximum input voltage = + 35 Volt DC  -----> NOT AC


LM7915
1 Ampere NEGATIVE voltage regulator
maximum input voltage = - 35 Volt DC  -----> NOT AC

Both should be heatsink-ed. Since it's only 1 Ampere, small to medium size heatsink should be adequate.

[jakenold]

ok.......a quick check. It's a 7815, so my measurement of 24 dc is incorrect also. (whoops). I'll recheck for the correct input (ac) voltage. Thanks, sorry about the confused info.

I do hope you rectify that AC before it hits the regulator.

Jake

[9 volts]

Thanks, so I was right to begin with, 24 dc. The heatsink gets really hot (brass post). The first 7815 blew, I figured it may be idea just to put a bigger heatsink in (the current one is a about 5mm wide2cm high)...like I don't want to replace the reg again in the very near future. (good idea?). Thanks again for the feedback

[axg20202]

Maybe. Bigger total surface area is what you're looking for. Have you used some hs compound between the regulator and the heatsink? It will improve the heat transfer significantly. If you've ever installed a CPU onto a motherboard, then you'll probably have some arctic silver kicking around - you can use that. Otherwise, order some regular hs compound when you order the new hs.

[slacker]

If it's a 7915 then you need to feed it -24volts DC if you run it off a positive voltage it won't work.

The tab of the regulator has the input voltage on it so you need to make sure the heatsink is isolated from the regulator or that the heatsink isn't touching ground or any other voltage.