Projects/LED Sign

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NOTICE. This page is still being worked on, and is not finished. Be aware of gaps, errors or complexities that need solving before proper use!

Contents

Purpose

This project is designed to provide basic training in using various tools and techniques in the space. At the end the student will have a nice looking LED sign to show off, as well as some experience with the equipment.

Example Sign

.

Skills

  • Inkscape.
  • Laser cutter design and use.
  • OpenSCAD use (basic).
  • Arduino programming.
  • Soldering.
  • Hand construction.

Materials

To complete this project you will need the following materials.

  • 8mm Clear Acrylic.
  • RGB LED strip.
  • Wood for base stand.
  • Power Supply.
  • Blank PCB.
  • Electronic Components.

Most/All of these should be available at the space.(TODO!!!) A donation to cover the replacement of them would be greatly appreciated, and allow for continued training schemes.

Guide

Step 1: Software

The first step to designing your sign, is getting the software. Most of the computers at the hackspace have it installed already. But if you want to install it on your own computer to work on it, you can download it for free.

The 2 programs we will be using are OpenSCAD, for the 3D design, and Inkscape for the 2D. Both these are open source and relatively easy to use.

OpenSCAD

[1] OpenSCAD is a 3D procedural design program. What this means is, rather than editing an object with the mouse. You program it with code. While this sounds scary, most of the work needed for this project is already done and you can download and use the end result quite easily.

InkScape

[2] Inkscape is a simple to use vector image program. What this means is, rather than making an image out of lots and lots of dots in an array, it makes it out of lines. This is exactly what the laser cutter wants to work with as well, making them a good match.

Sign Maker

File:SignMaker.zip This is the program that will make all the bits for your new sign. it looks scary when you open it, but is relatively easy to use.

Step 2: Sign Design

Mechanical

Now we have the correct software, we need to make a blank sign to edit. Load up OpenSCAD and open the sign maker program you downloaded previously.

Now at this point, you will be faced with 2 frames, 1 blank and 1 filled with a scary amount of code. Don't Panic. If you press F5 you should now have a nice image of what your sign will look like, on the right. You can zoom in and out with the mouse wheel, rotate with the left mouse button and translate with the right button.

If you look in the left hand window, you will see a section titled 3D Versions with 4 lines under it. If a line has // in front of it, it is inactive. Removing the // makes it active, adding it back deactivates it.

Change view_box(); to //view_box(); and //view_exploded(); to view_exploded();

if you press F5 again, you should now have an exploded view of the box. This shows you how all the pieces are fitted together. Feel free to change to the various views, to get a feel for how your sign will be made.

A little further down the window is the properties section. Most of these should already be correct for the materials, but if you can, measure the currently available material and change the numbers to match, it will avoid any issues later (Everything is in mm).

Below the Properties is the Sign Dimensions section. Here you can set the height, width and corner rounding of your sign. Remember to hit F5 after making any changes to update the view. Below these are the sizes of the base box. Initially, these are generated from the size of the sign. Feel free to change them to fixed values if you want. Though take care that everything will fit, and the sign will stand up when finished. The current values can be found in the little window just below the image.

The next section is the Base Options. This is where you set the various holes etc in the base box.

The first, and most obvious is the slot for the perspex. It often looks better set back a bit from the centre, it also leaves room of the electronics to fit in.

After this, we have the various holes for wires, switches, etc as well as hanging the sign up. You can set the size and location of these using the options here. They should be fairly sane to start with, but feel free to play and change to fit what you want.

The rest, below this is mainly model generation, and shouldn't be touched unless you know what you are doing. Feel free to have a nose and learn more about how the model works if you wish though.

Now we have the mechanical stuff sorted, we need a blank for the design to be put on to. Go back to the top, and activate the line

"projection(cut = true) perspex_outline();" (by removing the //)

and deactivate the other options up here. You now want to press F6. This will give you a technical layout, rather than the artistic one we were using previously with F5. You should now see the outline of your perspex (and only this) on the right window.

We now want to export the design out of OpenSCAD, so we can play with it in Inkscape. We do this by making a DXF file. Do to 'Design' (on the top row) and 'Export as DXF'. Save the resulting file (and make a note of where).

Artistic

Now we have the mechanical part sorted out, we want to be artistic with it. It's time to fire up Inkscape.

Once you have Inkscape opened up, you will be confronted with a blank page. We first need to import the DXF file we made in OpenSCAD. The import option is under the 'file' menu. Keep the import settings at default and you should now have the outline of your sign visible. It's likely off centre and a different size to the main frame though. To fix this go to 'file','Document Properties' and click on 'Resize Page to Drawing or Section'. Close this and you should have your frame neatly placed, with the page fitted around it. You can zoom in and out with the + and - keys.

Now is the time to get creative. There are 3 types of things you can add to your design, Text, Shapes and Images. In order to play nice with the laser cutter though, all 3 need some extra steps applied to them.

Text

Text can be added by clicking on the 'A' symbol on the left hand menu. Click where you want it and type away. Fonts and sizes can be set at the top. If you want to move it click on the arrow at the top left to select and move it. Once you are happy with your text, you need to convert it to a form the laser cutter will like. Select the text box (using the arrow mode), go to 'Path' in the top menu and click 'Object to path'. This will convert it from editable text to a bunch of lines the laser cutter software can handle.

Shapes

Much like text, Shapes can be added from the left hand menu. Each has various option and settings to play with. When you are happy with your shape, you need to change it to lines using the 'Object to path' button, just like text.

Images

Images are one of the most important parts of most people's designs. They are unfortunately also the hardest to laser cut though. Most pictures are arrays of dots. In order to be laser cut, an image must be converted to a bunch of lines. Inkscape can handle this though! :)

The first step is picking the image. You want a high(ish) resolution image. A small image is harder to convert and more likely to produce nasty and unwanted effects. You also want to avoid smooth colour changes as well. Black and white is best, but block colour can also be handled reasonably well. If there is an image you desperately want on a sign, and Inkscape can't do a good enough job, GIMP (Graphical Image Manipulation Program) can often be used to make it usable. This is a little outside this course though.

Once you have your image, you need to import it. You use the 'import' function your used previously (file, import). Now you have your image in Inkscape, you need to convert it to lines. Inkscape has a function set to do this called 'Trace Bitmap' in the 'Path' menu. Brightness cutoff is the default mode for this, and works well for black an white images, 'Colours' works better for block colour clip art. Hit update to see a preview of the new image, then OK to generate it when you are happy.

There is often a bit of confusion at this point. The new image has not replaced the old bitmap, but is position directly above it. If you click and drag the top image to one side you can see the original bitmap image. Click on it and delete it with 'Del'. Now you have your vector image, it helps a lot to see how it will look when laser etched. Select your vector image and bring up the 'Fill and Stroke' window (under the object menu). Under stroke, you want to select the 'flat colour' option from the top row of boxes (2nd in from left). This makes the lines visible, as they will be on the laser etch. Next go to 'Fill' and select 'No paint' (1st option). This removes any colour fills, since the laser cutter will not process these.

When it comes to etching, you can tell the software to fill loops as solids, if you want a line, both sides of the line must be lines, not just the line itself.

Other hints

While resizing, moving etc with the mouse is intuitive, it can be difficult to get stuff exactly centred and sized as you like. When the arrow is selected, at the top are the size options. X and Y are the coordinates of the bottom left corner of that element. W and H are the Width and Height of the element. If you click on the padlock, it locks the ratio of these 2 together, and so preserves the aspect ratio. Lastly the drop down menu allows you to change units. mm is generally the best options on these. These settings give you a lot more control and allow for exact positioning and centring. (To get the required X to centre something you take the width of the sign, subtract the width of the element you are centring and divide by 2.

You also need to remember that the bottom of the sign will be within the support box, anything etched here will be hidden.

Saving and Exporting

Now we have our sign ready, we need to save it in a format that the laser cutter can use. Inkscape normally saves as .SVG files. You should hopefully be saving regularly as you go along, particularly before converting to paths, since this can't be reversed.

To create a file the laser cutter can use, you need to export as a DXF file. Click on 'Save a copy' under the 'File' menu, it should default to .DXF, if not change it in the bottom right selection box.


Step 3: Laser cutting Sign

You should have 2 files from the previous parts. An outline to cut out (from OpenSCAD) and a design be etched (from inkscape). Load these onto a memory stick and head over to the laser cutter.

At this point you need a piece of Perspex slightly larger than your sign. If you are lucky they will be some pieces cut, next to the machine that will fit. The sign will be cut on it's side, so the height (generally the longest part) will be sideways. You want to peel off the protective coating from the top of your perspex, but leave the bottom one on.

Open up the laser cutter software (TODO - add exact software name), click import and import the outline DXF file. The outline of the sign should now be visible. Click on it, then on 'File', Engrave. This will bring up the control panel.

From here there are several settings you need to check are set correctly.

Click on Prop, this will load the properties menu. You want to adjust the cut speed to 5mm/s and the etch speed to 300mm/s. Leave everything else as is. (If they have been fiddled with, the exact settings are at the bottom of this document.) Click OK

(TODO)

Step 4: Stand Design

(TODO) 4.A : Designing the cut-paths for the sign base for use on the mill 4.B : Using the 3D printer to print base. 4.C : Using the laser cutter to cut base.

Step 5: Stand Manufacture

See 4

Step 6: PCB Manufacture

Using the PCB mill to cut and drill the PCB

Step 7: Soldering

Taking a made or provided PCB and populating it.

Step 8: Micro Controller Programming

Programming up the ATTINY85 for the main program, using an external programming board.

Step 9: Final Assembly

Putting the whole thing together.

Resources

Various useful resources for the project (designs, gfx, code etc).

Blank image files

(TODO) RLab logo in inkscape. (TODO) Basic sign shape in inkscape.

Base design files

(TODO)

Milling path file and 3D design

3D printer design and G-code

Laser cut box files

Electronics Design

The Positive Drive Board is designed for LED strips with a common Ground (driven high). The Negative Drive Board is for Strips with a common power (pulled low to drive).

Board designs are done in Eagle PCB File:RGB LED Drive PCB.zip

Positive Drive Board

Positive Drive Schematic Image
Positive Drive Board Image

Negative Drive Board

Positive Drive Schematic Image
Positive Drive Board Image

Micro Controller Code Examples

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