Category Archives: Nerdery

Saint Paul Public Libraries and

I’m not sure many folks know this, but I didn’t until I stumbled upon it: Saint Paul residents having a valid and up-to-date library card can access online training for free, and you don’t need to be in the library to use it (like you do for some references, like ALLDATA).

It can be a little confusing to sign in. This worked for me:

  • Visit and click “Log In”
  • Click “Sign in with your organization portal”
  • Type in and click “Continue”
  • Type in your “Library Card Number” and leave the “Password” blank
  • Click “Log In”

You should be in and may need to enter a little information to set up your profile.

Solving the refrigerator problem

We have a refrigerator downstairs that once in a while gets left open, and since it’s downstairs, we sometimes don’t catch it in time to save to food. Will and I decided to make something to help solve this.

Our plan is to use our Particle Proton (a tiny Wi-Fi development kit) and connect a temperature sensor. We’ll report that temp to “the cloud” and if the temp rises above some threshold, we’ll use IFTTT to text or call us to let us know to check the fridge.

I got us a free DS18B20 temperature sensor as a sample from Maxim Integrated (how cool is that?) and found some nice sample code here.

The prototype is now sitting in the fridge (photo above), dutifully sending out the temp every 10 seconds. The code is crazy simple.

Things we talked about while doing this:

  • Resistors in parallel and in series
  • Reading resistors
  • Analog-to-digital conversion
  • What numbers look like in binary
  • Trusting a component’s data sheet first
  • How to debug when Papa tells you to put the resistor in the wrong place

Refrigerator Problem_bb

UPDATE: The 2200mAh 3.7V battery didn’t last until morning, so Next up will be to see whether there’s a way to reduce power consumption. Fewer temp reports to the cloud will obviously help. I wonder if there’s a “low power mode”.

Saturday Morning Nerdery

Will and I have been working on some electronics fun, mostly because I wanted to try this Instructables using a microprocessor.

Of course, this was one of those things where you need to complete some projects in order to do the project. In this case we needed to build an AVR programmer so we could program the microprocessor (an ATtiny85). Building the programmer was fun, and Will did a whole bunch of the soldering!



Once that was done, we tried programming the chip…


…and the trashing began. It turns out I didn’t understand how to read the pinouts from the programmer. But once we got help and re-wired and re-tried, we finally got it working! We were able to make our NeoPixel Ring do cool things via this nice code.

One of the things we want to do with all this is help Jack have an “arc reactor” and “repulsers” for his Iron Man suit, so we needed an easier way to program and test our chips, because it was a little hard to work with wires for programming vs. wires for trying things…

IMG_2739 2

So this morning I made this…

IMG_2743 2

…which let’s me program and test easily without a bunch of jumpers and without having to keep moving the chip back and forth. Pretty sweet, and cost about $2 in parts (the board was $1.25).

And now we have easy-to-use joy. :)