Seriously, here are the full schematics.

Given that most of the hard work is done,at this point all that’s left is faffing about with the trace . Here are pointers to make said process easier:

OK, so all the pieces are accounted for; now to arrange them. Although this takes time, it isn’t hard and this part just serves to provide minor pointers so that you don’t end up with a stack of failure.

The thing you need to account for is how accurate your printer can be and how small of a circuit you think you may be able to pull off. Larger circuits may take up more space, but they reduce the chance of cross-feeding channels (small imperfections that may cause a bridging point for current flow). Luckily, EAGLECad has a built in error finding feature that will give a proximity warning for any connections that are too close to each other. Now on to trace and sizes: this chaser uses 10 LED’s and 5 power pins. 15 connections is a lot of trace management, for which I have a couple of rules (when not using SMD components. *Sigh*).

  • 1. Keep connections running between pins limited to just one. You may be tempted to use the paths between the soldering pads as paths for certain signals. Although not completely unviable, those soldering pins are relatively close to each other in the first place, so try to use that space wisely.
  • 2. trace sizes should be kept above 0.001 (inches? EAGLE Cad is very non-descript about which units it uses) to ensure that printing gives a usable result.Use 0.0016 whenever possible.

Side note: Although it was not something I have tried, using an inverted circuit scheme will save you a lot of etchant (at the cost of ink).

  • 3. Take into account that you are going to have to actually place the components and use your space accordingly. Components in tight spaces make for difficult soldering.
  • 4. If all else fails, lap it. Pretty quickly you should realize that working in a single direction makes a layout work out pretty well. I tend to work clockwise. There are exceptions to this rule, but if you’re stuck running out a signal line to a component, it may be worth consideringmaking a longer trace to bypass the trace s that block a particular path. The internal resistance of the copper won’t have a massive impact on the end result.


  • 5. Keep checking if there are any ways of improving a trace . EAGLE Cad isn’t perfect, so at times you may be faced with a situation where a trace doesn’t need to connect exactly where the schematic wants it to. In situations like these, it pays to know your layout.It may also end up saving a trace that would otherwise be blocked because of a badly placed trace node.

Now for printing the image:

Printing a circuit at home is easy enough once you understand the finer points of printing. One of those is that you have to consider the side of the board that you are going to use. Surface mounted components will always be on the same side as the copper, whereas through hole components will be on the opposite side. That would mean that SMD images (when being printed) would need to be inverted, whereas through-hole components will naturally flip the image, because it’s going to be mounted on the opposite side.In short, SMD schematics need to be flipped, and through-holes not flipped.

Skipping the whole printing and etching (because we have an entire article on that, dammit), you are going to want to place the components on the board. For that, you may want to keep a sheet with the layout nearby. It’s going to give the appropriate information on where components go, as well as (and this is the most important) their orientation. The sheet will also give a good reference point to how things should connect; if a pin looks suspicious then it should be easy to check via the sheet.

Also consider:

When the trace(ing?) is done you are going to have to transfer the print to a PC board.

Now if you’re wondering how to get the perfect result instantly, don’t. Save yourself the effort. This is going to take a couple attempts. Most of the time spent on this project will be trying to figure out what went wrong and how to fix it. Here are some troubleshooting shortcuts:

Print not staying on the board?

This one is tricky, because you have to figure out what went wrong. Most of the time it’s probably going to be a result of insufficient heat applied to the surface. The solution is obviously to just apply more heat and, if necessary, pressure. Alternatively, there may be something stopping the image from reaching the copper surface (check for surface oxidation).

Some other fixes that help as well is to include a solid border around what you are printing. The border (if adhered) will provide some protections against the surface tension of the paper, which can and will remove a smaller print if not guarded against.

Small flakes coming loose?

Rinse and repeat. If your trace is large enough, you may be able to cross the connection using a permanent marker, but if the trace is as small as we’ve used it will do more harm than good.But this is kind of a catch 22: if you have the savvy, then bypassing minor imperfections is possible. The choice becomes: use a decent print, or take the chance on another print which may be better, but also stands the chance of being worse. Always consider the risks.

Failure in all its glory (AKA, dealing with something going wrong):

After etching, there is not much you can do about something going wrong, but not much is still something. For example, on the through-hole board I managed to not place a ground line to a connection. The image was etched, so my choice was either to use this board or trash it.After looking at the schematic it became apparent that running an insulated piece of wire underneath the 4017 created an inconspicuous solution to the problem. The point is, although you may be faced with problems,some may have a solution beyond starting over.

Drilling:

Both the SMD and through-hole versions require component holes. Easy enough: Dremmel sells a drill set specifically for projects like these, and although not strictly necessary, a drill press is going to be hugely helpful. I managed without, but will admit that it made it a bit harder. Start with the smallest bit size (which will fit any basic wire pined components) and then work up from there. If you use a bit that is too large to start off with, there is a significant chance that the pad that you are trying to drill for will come loose.

This concludes our LED chaser. Any questions or comments can be posted on any of our social media accounts.

Next up: SMD and other nonsense.