Arduino Forum

Development => Other Hardware Development => Topic started by: Houser636 on Feb 14, 2015, 09:57 pm

Title: Arduino WIFI or Standalone using the ESP8266
Post by: Houser636 on Feb 14, 2015, 09:57 pm
Hello friends,

I just launched a kickstarter campaign.  I am building an ESP8266_12 breakout board.  It has a built in 3.3v regulator, and can even come shipped with the NodeMCU firmware.

https://www.kickstarter.com/projects/323660810/wifi-esp8266-iot?ref=category_popular (https://www.kickstarter.com/projects/323660810/wifi-esp8266-iot?ref=category_popular)

Please support and spread the word if you are interested.  Thanks!
Title: Re: Arduino WIFI or Standalone using the ESP8266
Post by: westfw on Feb 15, 2015, 01:05 am
It doesn't have enough heatsink space for the voltage regulator.
(there are a lot of similar boards that also lack enough heatsink space.  ~0.5W ((5-3.3)*.25) is quite a bit of power.  Sigh.)

Title: Re: Arduino WIFI or Standalone using the ESP8266
Post by: Houser636 on Feb 15, 2015, 09:11 am
What would you recommend?  I have not had any problems with this set up even running at 6.0V. It seems to dissipate heat nicely.  I could add a copper heat sink to the board if you think it is needed.
I think it is 6.0V at .250A and needs to dissipate 1.5Watts at full power.  The ESP8266 does not constantly consume .250A

E(J) = P(W) × t(s)

1.5X60=90Joules = 21.54 Calories

The specific heat capacity of copper is 0.092 calories per gram per degrees Celsius

Guess I should add a copper heat plain that is 234.16grams or 8.25oz.  I know physics dont lie, but I swear I have never had a problem with the mcp1700.  I think it can operate a bit above its max specs.
Title: Re: Arduino WIFI or Standalone using the ESP8266
Post by: westfw on Feb 15, 2015, 10:11 am
I would at least add as much copper around the regulator as you can possibly fit.
The board I was using apparently burnt itself out and started drawing .5A or so :-(
There are assorted app notes that suggest that ~250 mm^2 of copper (~15*15mm) is a big help (but not too much beyond that.)

Title: Re: Arduino WIFI or Standalone using the ESP8266
Post by: pito on Feb 23, 2015, 12:42 am
If you want to calculate the temperature of the linear voltage regulator package (an example):

P = (6V - 3.3V)*0.25A = 0.675W

T = Rthermal * P  +  Tambient

Let Rthermal is aprox 50 degC/Watt (ie SOT-89 package soldered to 1 square inch of copper)

T = 50degC/W * 0.675W + 25degC = 58degC

Thermal resistance of the SOT-89 against still air (no heatsink attached) is 330degC/W (=248degC for above example, the package will desolder itself from the wires).

Search for "thermal resistance" of various packages and heatsinks..