Hot/warm voltage regulator

I've attached an ESP8266 with an SD card component onto a Mega clone and noticed the voltage regulator gets really hot. I'm supplying an external 7VDC/500mA.

I then tested on an official Mega and the regulator is warm but not hot like the clone so I'm thinking the clone has a cheap regulator. If I unplug the ESP8266 from the Arduino the regulator cools down.

Does the more components you add to the Arduino, the hotter the regulator? More amp is drawn?

The regulator on a Mega is a linear regulator. Actually there’s two: 5V and 3.3V. You’re probably using the 3.3V and that’s really not equipped to drive a whole ESP8266. It’s only intended for running a few 3.3V sensors.

A linear regulator must throw away the extra power as heat. The current in and current out are the same. Just for the purposes of the equations, let’s assume it’s outputting 100mA at 3.3V. That’s 330mW power. The input is 100mA at 7V, which is 700mW. So there’s 370mW of power that the regulator must dispose of. That’s enough to heat it up to “Ouch! It burns!” hot.

(This is not entirely true as the 3.3V regulator uses the 5V power as its source.)

Ah, thanks for the explanation.

Any solution for this? Have another regulator just for the ESP8266 or a heatsink?

I don’t know a lot about the ESP8266 but I expect that it has some very large surge currents. It will be best to use an independent regulator for that. A switchmode regulator (AKA buck converter) can do this very efficiently. Pololu make some great ones.

The standard solution is an external 3.3v regulator for the esp8266. Get a 1117-series in TO-220 package (many manufacturers make them). Heatsink it if needed.

Or use a dc-dc buck converter.

Yeah, I’m thinking of using a buck converter for convenience and since the esp8266 and arduino will be in an enclosure/box.

Does anybody know if I’ll need to add or extend the wifi antennae since the esp8266 will be in a box?

If the box is conductive, reception will be a problem. If it's wood or plastic, it will be fine.


I really like these small AMS1117-3.3 modules, because they fit perfectly in the power rails of my breadboards:


One source for the modules PieterP mentioned...

(I've bought from that Amazon supplier... no regrets.)

Forgive me, those of you to whom it is obvious, but...

Be sure that your breadboard's power rails come in "blocks", i.e. they don't run the full lenght of the board, if you think you are going to use these easily as in the illustration. (And that you breadboard HAS power rails... many of mine fail one or both tests. Or just buy a suitable board! Probably worth it, if you've got to the point of wanting one of these voltage regulators1