5v L7805 Regulator Heatsink

Posted by under Electronics, on 21 October 2011 @ 5:34pm.

A recent project of mine is creating my own 5v regulators for charging mobile phones, etc. This will be incorporated into a battery box which I and my friends use when camping. However on this years trip we burnt out the 5v regulator we were using. For that reason I decided to make my own that would be more robust in comparison.

The biggest hurdle I’m hitting so far is dissipating enough heat away from the L7805 regulator (12v to 5v @ 1.5A). I am currently avoiding buying a “proper” heatsink for it as they cost in excess of £3 each. The regulator itself cost about 15p! It has been suggested by a friend that I use a “buck” style regulator instead which is significantly more efficient and does not require as much heat dissipation. This will likely be what I look at if I can’t find a suitably cheap solution to this issue. However as those themselves cost almost £3 each and require no heat sink in many cases it may be the better option.

At the moment I have been using strips of aluminium attached to the 7805 regulator along with heat paste (the same kind used on computer CPU’s). It extracts the heat just fine but the aluminium on it’s own isn’t enough to keep the temperature low. The load I am using on the regulator is just a 25w peltier chip (it’s the device that keeps portable fridges cool). However as a friend pointed out it won’t be running at 25w because of the lower voltage.

I have used 3 pieces of aluminium so far to extract the heat away and it seems to hold at a steady 90*c at 680mA, but as it’s not at full power, this is not going to be enough. I want to be able to extract at least 1A from it and still be below 90*c. A fan does aid this and keep it around 50*c but I’d prefer to omit the fan if possible.

5v regulator with home made heatsink
5v regulator current 5v regulator temperature (IN)

I’m considering ordering one of the buck regulators (LM2575 by the way) for testing. However everywhere charges a fair bit for postage so I’ll wait until I need other parts too.