This hat uses crime data to decide if your hood is naughty or nice.

Hat Displaying Animated Colors

The Sunday before Xmas I woke up with the great idea of building a blinky santa hat that would be a festive and silly thing to wear throughout the holiday. Looking outside at the record rains we’ve been getting I decided to see if I could build it out of components left over from other projects I already had lying around the house so I could spend my Sunday warm and dry.

Hardware

Digging through my storage boxes and junk drawer I managed to find the following:

Using a couple bits of protoboard and random hookup wire I connected two of the CR123A batteries in series to provide a 6.4 volt power source which I used to run both the ESP8266 and the LEDs.

The LEDs are connected to the ESP8266’s SPI (MOSI/CLK) pins.

Electronic Components

I was slightly concerned about putting 6.4v into the LEDs as the datasheet says not to give them more than 6 volts, but it seemed to work just fine. Your mileage may vary; there are a large number of APA102 clones on the market some of which are of dubious quality.

The ESP8266 is a 3.3v device, but the breakout board included a voltage regulator which can handle stepping the 6.4v down to a stable 3.3v. Overall this board is a good deal for a Made-in-the-USA full featured ESP8266 breakout, but it it does have a couple of problems. It doesn’t expose a pin for the VIN for the voltage regulator so I had to solder in a jump wire to power it from a non-USB source. Additionally, it uses the older-style mini-USB connector rather than micro.

After soldering everything together, and checking the connections, I rolled it up into the brim of a santa hat and the hardware was complete!

Components Installed in Hat

Software

The ESP8266 shipped with NodeMCU pre-installed so I wrote a quick 10 lines of lua to light up each led to ensure everything was working as expected. When I tested it out, I was pleasantly surprised with how well the faux-fur around the brim of the hat diffused the LEDs. Success!

Hat with one LED lit at a time

Initially this was all I had planned for this project, but the ESP8266 includes a wifi radio and TCP stack, so I might as well add a santa hat to the Internet of Things. Sticking with the theme, I decided I wanted the hat to use it’s internet connection to act as a “naughty or nice” detector.

After a few minutes of looking at available APIs, I stumbled across SpotCrime and their API which aggregates crime data from many agencies and sources into a common format (SpotCrime Open Crime Standard (SOCS)). TL;DR you make an HTTP GET providing your lat/lng and you get back a JSON document with all the crimes in area over the last 7 days.

Now I just needed to find out how to have the ESP8266 figure out where it was. I planned to tether the hat to my phone while I was away from the house so I didn’t want to trust IP geolocation; I needed something more accurate. Thankfully Google provides the Google Maps Geolocation API which allows you to provide a list of BSSIDs nearby and it will approximate your location.

Now that “the cloud” was doing all the heavily lifting for me, I just had to write the code to tie it all together. I decided to put as much of the code on the server as possible. Given my prior experience with wireless deployments, I don’t trust a tethered connection to a mobile phone to be reliable or robust. Limiting the amount of data I send/receive over the wireless link would be critical to having the hat actually function in the real world.

Server

I wrote a tiny webapp in Python using Flask which accepts a simple string of data from the ESP8266, handles the API calls to SpotCrime and Google, processes the results to determine if an area is naughty or nice, and returns a simple naughty/nice/unknown response to the ESP8266. I hosted the app on Google App Engine for free.

Client

I then wrote a very simple client in lua which attempts to connect to my phone’s hotspot and update it’s location and naughty/nice status every 5 minutes by talking to hat.py over the internet. If the local area is deemed “naughty” the hat flashes red, if it’s a “nice” hood the hat flashes green. If it can’t determine, or if the internet is unavailable, it defaults to a nice white/red/green fill loop.

This code was then flashed onto the ESP8266 using nodemcu-uploader.

You can get the code on Github but please consider it POC quality at best!

Real world performance

Knowing that the ESP8266 can pull upwards of 200ma when transmitting, and that the LEDs were using ~400ma; I was pleasantly surprised with the runtime of 3 hours I got out of a pair of 5 years old 1400mah batteries. I did notice that after extended use the batteries would become very warm to the touch. I don’t know what the maximum current draw from these cells is, but it’s quite possible I was exceeding it when all the LEDs were lit full white.

I’d estimate the hat was able to update it’s crime data successfully about 90% of the time. Failures were mostly related to associating with my phone’s hotspot. When that did occur, a quick reset would fix it, which was simple thanks to the reset button on the breakout board, which I could easily press through the hat.

Summary

Considering I only put about 6 hours of work into it, the hat turned out great, and I was very happy with the performance. It was amazingly bright; I was asked to turn it off in a dimly lit restaurant, and I received dozens of compliments / questions while wearing it in public.

Santa even decided to wear it while doing Christmas Karaoke:

h0 h0 h0