LED Logo

A lot of my build is based on ideas and work done by brewers on Homebrewtalk.  One of the members there Kal, has also put up a wonderful site documenting his build at The Electric Brewery.  To add a little flare to my control panel I have built a LED lighted version of Kal's logo.  The panel is not finished yet but here is the Logo so far.

  
This will be attached to the back of the control panel face and will show through a hole cut in the panel.  There will also be a small frame around it.  This is how I built it.....

I started by printing out Kal's logo as a mirror image.  It needs to be mirrored because you will be engraving it from the other side and that way it will be the correct way around when you are done.  I cut 2 pieces of 1/8in acrylic to the proper size.  I used a dremmel tool with the flex extension and a 1/32in engraving bit to 'etch' the image.  The flex tool allows you to use the dremmel sort of like a pencil.

I then attached the printed logo using some tape and went over the image with the engraving tool.  It takes a little practice at first because the image is seen though the thickness of the acrylic.  You do not have to go very deep.  Just go over the image slowly and cover everything.  Be careful because the tool wants to 'pull' in the direction of the spin.  It may be useful to practice on a scrap piece first.  I did the lettering on one sheet of acrylic and the hop on a 2nd sheet.  This way I could make them 2 different colors.

Above are 2 pictures after etching.  There is a lot of debris from the engraving in the pictures but that cleans up easy.

Here are the two pieces held together.

On to the LEDs.  To wire the LEDs we need to know a couple of things.  The forward voltage, the current draw and your supply voltage.  Also note LEDs want DC power.  The current and voltages can usually be found on the suppliers spec sheets. 

 In my case I have 3 types of LEDs.

The White LEDs are 3V 20ma
1 Green LED is 3.6V 20ma
1 Green LED (slightly different color) is 2V 30ma

I am using 12V as the supply.  Because 12V is too much for the LEDs we will attach resistors inline with them to control the voltages/current to the proper amount.  This is calculated using Ohms law which states:

Current = Voltage/Resistance or Resistance = Voltage/Current

We have 12V and the 3 LED string uses 9V (3 LEDs x 3V) so we need to dump 3V to keep our current at 20ma.  So 12-9 =3V   3V/.02A = 150.  We need a 150ohm resistor.

You can find many LED calculators on line to figure out the resistors needed for your LED voltages and current.

The letter sheet will have a string of 3 LEDs running across the top and 3 along the bottom.  The hop sheet have 1 above and 1 below.  That's basically 4 circuits.  Two strings of 3 and 2 strings of 1.  These 4 (series) strings are then connected to each together in parallel.  You can see below the resistors used for each string.

The three string runs have the 3 LEDs in series.  In this case the voltages are added and the same current is drawn through the circuit.  In this case, 20ma.  We then attach 4 strings together in parallel which means the entire circuit will draw the sum of the currents or in our case 20ma + 20ma + 30ma + 20ma = 90ma total.  Our power supply will need to provide at least 90ma.  To attach the lines in parallel we attach the 4 12V ends to the power and the 4 ground ends to ground on the power supply.

Ok enough about math and stuff.  I modified the LEDs by grinding down the face and the sides so it was a square shape the thickness of the acrylic and then cut notches in the ends of the acrylic the correct size with a dremmel and glued the LEDs in place with styrene cement.  Remember LEDs must be connected with the correct polarity or they won't work.  See the above crappy picture for a before and after shot.

I used a small Radioshack project board to have a place to connect the power supply to the circuit and also for a place to put the resistors.  It's not a necessity but it can be a pain trying to solder the resistors onto the wires so I did it this way.  There is also terminals to tie everything to the power.  Top and bottom views follow. 

In the top picture the top terminal connects to the power supply and the left one connects all the power lines from the circuit to power.  The right side connects all the grounds to their appropriate resistors and then all tie to the ground back to the power supply.

To hold all this I made a small 'box' out of styrene and painted it black.  The circuit board is held to the back of the board with some nylon standoffs. I started with a sheet of 2mm styrene and some .250 x .100 sticks of styrene (like model plastic).  I made it big enough for the sheets to fit in it with clearance for the wire on top and bottom.

 

The next picture shows the final product.  I drilled small 1/8in holes in the top and the bottom of the sides for the wires to come through.  I also notched the 4 corners of the acrylic sheets so a screw can pass through and attach the unit inside of the control panel.

The power supply I used for this is an old 12V 'wall wart' from an old Linksys router.  I just cut off the connector at the end and attach it to the circuit board with the screw terminals.  As you can see in this picture it is 12V and up to .5A or 500ma. (click the picture)

Well that's about it.  I will follow with some pictures from the build and some more or less 'finished product' pictures.  My panel isn't painted yet nor is the small frame around the logo.  Also note it is very hard to get good pictures of this thing because of the lighting.  Flash tends to wash it out and no flash pictures are dark and tend to be blurry.  click any pictures to see a larger version of them.