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Topic: External power regulator getting really hot (Read 1 time) previous topic - next topic


Hi, I'm pretty new to electronics and am still learning a lot everyday. This stuff is really fun!

However I got one problem I just don't understand. I'm trying to control a ledstrip with a Arduino UNO and a ethernet shield. With the 12V directly into the Arduino, the regulator next to the connector got really hot.

Now I got a L7805CV regulator that I use, that is capable of 1.5A. As soon as I connect the Arduino and ethernet shield, the regulator heats up, just like it did with the regulator on the arduino itself. The only thing that is connected, is the Arduino.

How can I use this regulator to get 5V without overheating? Am I missing something? I probably do, but what ;) It must be possible to run this without a mighty big heatsink?

I've also checked a simple ledstrip controller from China, which got a LM78L05 regulator (100mA). That one doesn't get noticeable warm. It even sits in a small, completely closed box. I wouldn't dare doing that with my own project now.


The ethernet chips takes quite a lot of current.  The regulator has to drop 7V from 12V down to 5V, so if the current is, say, 150mA then the regulator will dissipate over 1 watt.  A small heatsink on an external regulator is a good idea...  Alternatively use a 9V external supply or a _regulated_ 5V external supply (USB charger perhaps?).
[ I won't respond to messages, use the forum please ]


Also without the ethernet shield, the regulator gets really hot. Even with a heatsink it's very uncomfortable to touch. When I connect the USB to the arduino to program, the regulator cools down quickly.
I need the 12V for the led strip and I don't want to use 2 powersupplies.

How come, for example, this little smd regulator in the ledstrip controller can give 5V without getting extremely hot? Is this because the current needed to power the controllerchip is much lower and thus the heat dissipation is less? I also noticed the controller has a little 47ohm resistor between the Vin and capacitor.


Can you measure with a DMM how much current it draws?

Add a second voltage regulator to bring the 12V to 7V or so. That could have a separate heatsink too.
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)


7V isn't available in standard chip ranges, 8V is, and is closer to being midway between 12 and 5
[ I won't respond to messages, use the forum please ]

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