Huzzah Wi-Fi module (or emonTx v3.4) overheated?

Hello from south of France.

We reached 40°C yesterday afternoon, my outdoor EmonTx V3.4 + Huzzah WiFi breakout is in a closed enclosure in full sun and… It seems it didn’t like it.

The problem seems to be around power supply and the Huzzah WiFi breakout.

Once the EmonTx is plugged in (on my desk) with both AC and DC (checked, correct 5V) and I plug the Huzzah breakout in, the module blinks a couple of times then lights up (Wi-Fi is OK, I can ping it).

The breakout gets very hot near the UART connector (don’t know if it was the case before).

After a very short time (2 to 6 seconds, seems to depend on how the breakout is hot), it goes down (no more light, no more Wi-Fi).
I have to remove it and plug it back in to work again ; if I don’t wait enough for it to cool down a bit, it doesn’t boot (no blinking LED at all).

In order to check EmonTx was correctly booting, I plugged a USB-UART interface and after a reset, here’s what I get:

emonTx V3.4 Discrete Sampling V2.90
No EEPROM config
RFM69CW Node: 7 Freq: 433Mhz Group: 210
POST…..wait 10s
‘+++’ then [Enter] for RF config mode
CT 1 Cal 90.90
CT 2 Cal 90.90
CT 3 Cal 90.90
CT 4 Cal 16.67
RMS Voltage on AC-AC  is: ~266V
AC-AC detected - Real Power measure enabled
assuming pwr from AC-AC (jumper closed)
Vcal: 268.97
Phase Shift: 1.70
NO CT’s detected
No temperature sensor

I’ve double-checked, the USB power is OK (5V on the UART when Huzzah breakout plugged in) and the jumper is open (removed).

If I plug the AC cable only, the EmonTx doesn’t boot (no light). Unless I close the jumper (but this way the Huzzah module cannot boot).

If I connect the Huzzah Wi-Fi breakout to my UART interface, it boots correctly then stops, exactly like when it’s connected to the EmontTx.
I think the Huzzah is the culprit.

Any idea of additional tests I could do to sort this out?

I’m going to buy a new breakout module (I can’t find them anymore on the shop) then I’ll have to program it (with EmonESP).
Anything I should think of now (while ordering stuff)?


Hello David

That’s nice and warm and Im sure quite a bit hotter in the box! :sunglasses:

No should be cool, never noticed any part get particularly warm.

Could you post a picture of the Huzzah? It sounds like it’s probably beyond fixable if it’s overheating… sounds like a short of some kind…


It’s really really hot, I can’t keep my finger on it (between the two switches).

Here’s a picture (sorry, no macro mode), it seems normal.

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The device between the switches is a voltage regulator.
Getting so hot it can’t be touched likely means it’s bad.

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Yes sounds like a blown regulator! AP2112k-3.3v regulators, might be tricky to de-solder? but could be an option?

I’ve ordered a spare breakout, this will get me to learn how to program it.

I’m going to order some regulators (seems very cheap), a new super-thin tip for my soldering iron and I’ll try my (de)soldering skills on it. Can’t be worse than today anyway :sunglasses:

Or a hotgun maybe. Now I definitively need one!


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According to the Adafruit schematic, the regulator is a AP2112k-3.3. The maximum input voltage is 6V. This regulator has built-in over-temperature protection and Foldback Short Circuit Current Protection, so in theory it should be hard to damage - unless it has just failed!

The regulator supplies 3.3V to the EPS8266 (ESP12) WiFi module.

The regulator could get hot because:

a) it has failed
b) the ESP8266 WiFi module is drawing too much current. The EPS12f spec says the 3.3V average continuous transmission current is ~71mA while the peak is 500mA - a significant increase. Not sure what effect the firmware has on this.

I’m not sure if there is an easy way to check which reason it is, without removing the regulator and testing it, or trying a new one. If the reason is b), the replacement regulator will get hot too!

Good luck!

My bet would be it isn’t the regulator, but something else drawing excessive current - presumably just less than the point where foldback happens.

I’d expect a failed regulator to be cold - either almost a short-circuit or open-circuit, in each case dissipating little power.

That’s the logical conclusion, but I’ve had at least one fail in the same manner the OP’s
board is acting. i.e. get so hot you can’t hold a finger on it.

One I remember quite vividly because it got so hot it was actually quite painful when I touched it. The board where the reulator was mounted was discolored too. ('twas on a BeagleBoneBlack Single Board Computer) The odd part was the SBC operated fine one day, then the next day after powering it on, it wouldn’t boot. That’s when I found the hot VR chip. No changes were made to the board or the loaded firmware, so I can only guess it simply died.
Well, something died. Maybe not the VR, but the result was an overheated chip.