Wednesday 8 April 2015

More work on the CaptiveIntraweb - ESP-01 NodeMCU

With all basic programming issues out of the way, I built a first prototype of a somewhat oversized Wifi-throwie. Schematics will be published in one of the next posts.

There is a 1N4001 diode hidden in the red heat-shrink tubing to get rid of about 0,6V. It might not be the most energy efficient way to drop a few thenths of volts, but it sure is cheap.
For the power consumption I measured 70mA. That is A LOT!
With an estimated realistic capacity of around 1000mAh, my Ultrafire battery will only give me a 14h run time.
Not really spectacular.
This also makes it rather inefficient for a tiny WiFi-throwie. A CR2032 has around a capacity of around 200mAh, giving us only 3hrs of fun.
ESP8266 sleep modes (according to the WIKI) do not work in SoftAP mode. So the only thing that helps is a bigger battery.

Battery options:

  • CR2032 (3V / 200mAh) < 3h
  • 14500 Lithium cell (3,7V, 800 mAh) > 10h
  • 18650 Lithium call (3.7V, 2000 mAh) > 28h
  • Energizer L92 (1,5V, 3000 mAh) > 40h
I have some unused, low quality 18650s, matching battery holders and a suitable enclosure, so I'll stick with them,

  • 18650 battery (well, nothing really but let's say:) = 2€
  • ESP-01 = 3,30€
  • Battery holder = 1€ (less)
  • Dupont cables = 1€ (less)
  • Enclosure = 1,30€
  • 1N diode = 0,10€ (less)
  • Rare earth magnet = 1€
So I get away with less than 10€ (also less than 10$ US) - Cheap enough to put at risk in public places. That is why I shy away from good quality 18650s.

The code on github is a bad mess of English and German fragments. The next step is to clean up the translations.


  1. Hi,
    I have built it on a ESP8266 v01, it works well.
    Mine is a bit bigger, since I use a 7.2V 1100mAh Liion Pack (from Pollin) with built in protection and a cheap buck converter to 3.3V. Now I am trying to write some other games, like nim, guess the number, mastermind. But I am new to HTML and Java Script, so it will take some more time to get it work fine.

    1. How long does your battery pack last?
      Also: If you get any new content to work, please drop me a line.