Coffee Table Hacks

An Engineer's View on the World

Adding lights and a microcontroller to a project

For my next trick, I will attempt to add lights and an Arduino microcontroller to the coffee table.  *drum roll, please!*

Table-LEDs-4-Small

Table-LEDs-2-Small

Table-LEDs-3-Small

So how did I do this?  Let’s start with a (very) quick background on programmable microcontrollers.  These little guys have been around for a long time in various forms.  Reduced to its basic concept, they are an embedded microcontroller development platform on which a user can write some easy-to-understand programming code that takes some electrical input (sensors, potentiometers, etc), processes the data by the code specified, and provides some output (usually in the form of lights, relays, motors, etc).  That is an over-simplification of the capabilities, but once you understand how to program the microcontroller to complete these basic steps the possibilities become endless!!  I have included a few links at the bottom of this post for further reference.  For this project, I am using an Arduino Yun.

ArduinoYunFront_2_450pxYunParts

First, I had to add the lights.  For this project, I chose to use 2 meters of WS2812 R-G-B LED strip lights from Adafruit (Link), in part because Adafruit provides a free Arduino-compatible header file… more on this later.  I cut the LED strips into 4 segments, added a few soldered-wire leads to connect the segments, and affixed them to the underside of the table with double-sided adhesive tape.

Table-Circut-2

 

Powering the LED’s can be a challenge.  There are 120 tri-color LED’s in this project.  Each LED can draw up to 60 mA of power (20 mA per color component) at full brightness.  At a peak current draw of 7.2 amps (36 Watts at 5 volts), that is a lot of juice!  A more reasonable average current would be 20 mA per LED (one color at any moment in time), resulting in a current draw of 2.4 amps (12 Watts at 5 volts).  Either way, this power draw exceeds the Arduino specifications for it’s 5-volt V-out pin.  Consequently,  I chose to power the LED’s with a wall wart (finding one at Radio Shack that offers a 5V DC + 5V USB port with support for up to 5 Amps, so I can power both the LED light strip and the Arduino off the same power outlet).  Following the instructions on Adafruits website, it is also recommended to add a large capacitor across the power supply and a resistor in-line with data signal so as to protect the LED string from harmful spikes in voltage.  **For a more detailed explanation, see Adafruit’s website (link below.)**

Table-Circut-1

I will write another post detailing some of the programming options and possibilities! Stay tuned.

Reference Links:

Arduino Homepage

Adafruit WS2812 LED Installation Guide

Arduino Project Ideas 

First Post: Building a Coffee Table

What would a blog called “Coffee Table Hacks” be like without a coffee table?  So, I thought a good place to start would be to build a coffee table!  As my first adventure with woodworking, it has been few months in the making.  I am finally ready for the big reveal. First, we’ll start with the final product.  My design goal was to incorporate an aspect of wine (another hobby).  This gave way to a wine rack hanging below the glass table top.

Final Table (1 of 2)   Final Table (2 of 2)

As a shameless plug, I have been taking classes in woodworking at the Washington DC-area Tech Shop (www.techshop.ws).  I started by sketching the design out.  A friend had plenty of extra raw oak lumber that I was able to use.

Building-1

Building-2

Once a design was established, I had to use a jointer, planer, and table saw to cut the raw lumber into flat planks of useful wood.

Building-16

Building-15

Building-3

Building-4

I decided to use mortise and tenon joints for the table legs, aprons, and wine rack supports.  I was fortunate enough to have access to a chisel-hallow mortiser to cut the 1/2″ mortise holes.  The tenons were cut with a band saw.

Building-6

Building-7

Having only 3/4″ planks of lumber, I had laminate (3) planks together to form the 2″ x 2″ legs.  Once the joints and legs were cut, I was able to glue all the base pieces together.

Building-9

Building-5

The wine racks were cut out using a ShopBot Alpha CNC machine. This thing was incredible!! While I do not have photos of the top, I used a table router to cut the 3/8″ edge round-overs and a 1/4″ rabbet for the glass tabletop to sit in.  All that was left to do is stain!!

Building-8

Building-10

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