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Topic: Heating issue (Read 802 times) previous topic - next topic

komarek

hi guys
so i just finished this new quite complex project with Esp8266 on NodeMCU

a smart box which can do many things:

- open the door and turn light on (through MQTT)
- check if the gate is open (MQTT)
- has 2 status LED
- has a Oled display (128x64px)
- track my 2 websites visitor (through MQTT request and a python script on my raspberry)
- check the temperature and Humidity with a DHT11 module
- has 3 buttons (to open door, turn light, change screen-mode on the display)
- control the room light level (with a LDR module)

so i used all available pin ( i guess)

i just realized that the cpu is really heating... i tried to keep it turned on for about 5/10 minutes but i m quite scared to go longer...
i am powering the device with a dc external supply of 8 volts through the VIN.. but i checked that the device is heating anyway if i power it through the usb port.

what you think about?
am i risking to brick it?

cheers
 

Wawa

No direct experience with this board, but I know the ESP8266 module is drawing about 80mA in AP mode.
About 1/4watt of heat for that part.

With 8volt on V-in, the regulator (part in the middle) has to drop 8volt - 3.3volt (board supply) = 4.7volt.
The 3.3volt regulator will consume 4.7*0.08 = 0.376 watt, powering the ESP module only.
More (= hotter) than the ESP module itself.
That doesn't even include powering the USB chip?, the Oled?, and the sensors.

The regulator has little heatsinking on this small board.
The solution is a lower supply voltage.
Try a 5volt cellphone charger, plugged into the USB socket.
Leo..

komarek

as i said
i tried with the usb plug
but it is heating alot anyway

what would be the problem?
a wrong bond in solderings?

Wawa

What is getting hot. The 3-pin part in the middle or the metal square.

The metal square gets rather warm, and this is normal.
Warmer in access point mode than in station mode (depending on router settings).
Only cold in deep sleep.
Leo..

komarek

What is getting hot. The 3-pin part in the middle or the metal square.

The metal square gets rather warm, and this is normal.
Warmer in access point mode than in station mode (depending on router settings).
Only cold in deep sleep.
Leo..
yes specially that 3-pin part in the middle (i guess the regulator) gets really hot almost immediatly, you can't even touch it with your finger...
and after 40/60 seconds the big part in the middle with writings (i guess the cpu) is getting warm and after a while quite hot too

Wawa

You could post a circuit diagram, showing how everything is connected, so we can check.
And a links to the Oled and sensors.
Leo..

komarek

You could post a circuit diagram, showing how everything is connected, so we can check.
And a links to the Oled and sensors.
Leo..
ok
i will do it today
it's gonna be a few hours job :)
what's your idea at the moment?
and... it is better not to turn the device ON for long time at the moment?

ElCaron

#7
May 04, 2017, 04:42 pm Last Edit: May 04, 2017, 04:46 pm by ElCaron
The 3pin part is the LDO voltage regulator, which immediately burns about 1/3 of the energy your device takes (or half of the energy your components take). That might be the issue.
The ESP it self also gets rather warm. Not untouchable hot, but enough to seriously fuck up temperature reads of adjacent sensors, even with free air circulation.

Perhaps this is for you: https://forum.arduino.cc/index.php?topic=445951.msg3149938#msg3149938
You could even skip the LDO I planned into this entirely, but at least, you could almost halve the dissipation on the LDO by getting the voltage to 4.3V before the AMS1117. Or find a SOT-223 LDO with an even lower dropout voltage. You would need to power with more than 5V, but that doesn't matter, since it is switched down, not burned.
The Board is published at https://github.com/kvoit/WemosD1MiniPerfboard

BTW: The DHT11 is terrible garbage. The DHT22 is usable, but I like the BME280 better. If your OLED is I2C, than you wouldn't even lose pins for it.

EDIT: Looking at the used components, that project SHOULDN'T take that much current. The DHT11 takes virtually nothing, the OLED isn't excessive, neither are the LEDs ... You should measure how much current it takes, e.g. using something like this: https://www.amazon.com/Eversame-Multimeter-Chargers-Capacity-Banks-Black/dp/B01D9Y6ZFW/ref=sr_1_2?ie=UTF8&qid=1493909200&sr=8-2&keywords=usb+power+meter

komarek

hope u can read that

Wawa

Diagram look Ok.
As said, you only need 5volt on V-in.
Anything higher is only heating up that LDO more.
Why that 8.5volt supply. Existing supply, batteries?
If you HAVE to use it, then a buck converter is the coolest way.
You can even step directly with that to 3.3volt e.g. with this one.

Next time, connect the switches between pin and ground, without external resistors.
Use the internal pull up resistors in pinMode: pinMode(switchPin, INPUT_PULLUP);
Invert all switch logic (HIGH becomes LOW, and LOW becomes HIGH).
Leo..

komarek

Diagram look Ok.
As said, you only need 5volt on V-in.
Anything higher is only heating up that LDO more.
Why that 8.5volt supply. Existing supply, batteries?
If you HAVE to use it, then a buck converter is the coolest way.
You can even step directly with that to 3.3volt e.g. with this one.
well i m using an old charger of some mobile or something... it's all i have... and it's 8.5 v out.
at the  moment i m trying to find somethingelse. but, as i said, it's pretty strange that the device is heating alot also when powered by the usb port to the computer.

Quote
Next time, connect the switches between pin and ground, without external resistors.
Use the internal pull up resistors in pinMode: pinMode(switchPin, INPUT_PULLUP);
Invert all switch logic (HIGH becomes LOW, and LOW becomes HIGH).
Leo..
yes i know.
sometimes i use it

Wawa

Things that use power do heat up.
That 3-pin LDO should be able to handle "just too hot to touch" (~65C) indefinitely.

With a USB/5volt supply, the LDO is using 33% of the power of the board, with 8.5volt that rises to 60%.
We know about the ESP module (80mA), but we still don't know how much that Oled is using.
Leo..

komarek

We know about the ESP module (80mA), but we still don't know how much that Oled is using.
Leo..
yep sorry

that's it
https://eu.banggood.com/Wholesale-Warehouse-0_96-Inch-4Pin-White-IIC-I2C-OLED-Display-Module-12864-LED-For-Arduino-wp-Eu-958196.html?rmmds=myorder

Wawa

The Adafruit site mentions an average current draw of 20mA for that Oled.
Leo..

komarek

The Adafruit site mentions an average current draw of 20mA for that Oled.
Leo..
:) i see
so?

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