Skip to main content

A Totoro to forecast the weather

Regular readers may know that I like ambient devices: devices that fit into the environment unobtrusively and provide information at a glance. One such device is my bus monitor that shows times of buses at the stop near my house.


Recently I decided to solve the problem of answering the question "Do I need an umbrella?" when I leave the house. For this I chose to use an ESP8266 in the form of a NodeMCU running Lua and display the coming weather by illuminating the eyes on a small Totoro figure.


This was my first NodeMCU/ESP8266 project and there's definitely a bit of a learning curve. I ended up using luatool to upload my Lua code to the device, and esptool to flash the firmware using a custom firmware build from this wonderful website with the following modules present: cjson, file, gpio, http, net, node, tmr, uart, wifi, and ws2812.

./esptool.py --port /dev/cu.SLAB_USBtoUART write_flash -fm qio 0x00000 nodemcu-master-10-modules-2017-04-08-20-28-08-integer.bin

The first step was to prise open the Totoro figure and then drill out the eyes so that two LEDs cut from a NeoPixel strip could be hot glued in place.



I made a mess of opening the bottom of the Totoro as I didn't realize there was a large chunk of resin in the bottom (for stability). However, I ended up with a nice hole through which it's possible to connect a USB cable for reprogramming the NodeMCU.


The rear part of the Totoro contains the NodeMCU with just five wire connections: power, ground and data to the NeoPixel strip, and a pig tail to supply power through a hole drilled in the back (5V from an old wall wart I had lying around is fed straight to Vin and GND on the NodeMCU).


I used heat shrink tubing to insulate the connections so that there aren't any inadvertent short circuits when the Totoro is closed.

The code that runs Totoro is here. It uses the Met Office's DataPoint API to get the weather forecast for a location in the UK. You'll need to register there for an API key and figure out the location you want to get weather for from the Met Office data. As coded it gets the weather forecast for a maximum 6 hour period (two 3 hour forecasts) and figures out the worst weather to happen during that time.

The configuration for the Totoro is all in totoro-config.lua where you'll fill in the weather location, API key and the credentials for the WiFi network you want your Totoro to connect to.

The Totoro conveys the following with its eyes:

  • Red: heavy rain
  • Blue: rain
  • White: snow
  • Flashing white/black: hail
  • Yellow: sunny
  • Flashing red/blue: Internet or API connection problem
  • Flashing green: updating weather forecast
  • Black: no special weather
Here's Totoro having trouble reaching the API (flashing red/blue).


And here's Totoro checking the weather (flashing green) and finding that it's nothing special (goes black).



Comments

Unknown said…
Incredible Totoro-T1000! :)
Inspired by you, I am thinking about robotizing my Android-G-Cloud doll.
Could you tell me the size of your Totoro? Guessing it from your photos is hard.
It's this figurine: http://www.ebay.co.uk/itm/My-Neighbor-Totoro-Figure-STUDIO-GHIBLI-Totoro-with-Umbrella-Resin-Action-Figure-/112016116132

About 10cm tall

Popular posts from this blog

Your last name contains invalid characters

My last name is "Graham-Cumming". But here's a typical form response when I enter it:


Does the web site have any idea how rude it is to claim that my last name contains invalid characters? Clearly not. What they actually meant is: our web site will not accept that hyphen in your last name. But do they say that? No, of course not. They decide to shove in my face the claim that there's something wrong with my name.

There's nothing wrong with my name, just as there's nothing wrong with someone whose first name is Jean-Marie, or someone whose last name is O'Reilly.

What is wrong is that way this is being handled. If the system can't cope with non-letters and spaces it needs to say that. How about the following error message:

Our system is unable to process last names that contain non-letters, please replace them with spaces.

Don't blame me for having a last name that your system doesn't like, whose fault is that? Saying "Your last name …

All the symmetrical watch faces (and code to generate them)

If you ever look at pictures of clocks and watches in advertising they are set to roughly 10:10 which is meant to be the most attractive (smiling!) position for the hands. They are actually set to 10:09.14 if the hands are truly symmetrical. CC BY 2.0image by Shinji
I wanted to know what all the possible symmetrical watch faces are and so I wrote some code using Processing. Here's the output (there's one watch face missing, 00:00 or 12:00, because it's very boring):



The key to writing this is to figure out the relationship between the hour and minute hands when the watch face is symmetrical. In an hour the minute hand moves through 360° and the hour hand moves through 30° (12 hours are shown on the watch face and 360/12 = 30).
The core loop inside the program is this:   for (int h = 0; h <= 12; h++) {
    float m = (360-30*float(h))*2/13;
    int s = round(60*(m-floor(m)));
    int col = h%6;
    int row = floor(h/6);
    draw_clock((r+f)*(2*col+1), (r+f)*(row*2+1), r, h, floor(m…

The Elevator Button Problem

User interface design is hard. It's hard because people perceive apparently simple things very differently. For example, take a look at this interface to an elevator:


From flickr

Now imagine the following situation. You are on the third floor of this building and you wish to go to the tenth. The elevator is on the fifth floor and there's an indicator that tells you where it is. Which button do you press?

Most people probably say: "press up" since they want to go up. Not long ago I watched someone do the opposite and questioned them about their behavior. They said: "well the elevator is on the fifth floor and I am on the third, so I want it to come down to me".

Much can be learnt about the design of user interfaces by considering this, apparently, simple interface. If you think about the elevator button problem you'll find that something so simple has hidden depths. How do people learn about elevator calling? What's the right amount of informati…