If you don’t feel up to doing the whole damned schematic yourself, here’s the shortcut. Check our acid etching articles for even more shortcuts!

So now you know how to print an image on a PC board. But what use is knowledge if it brings no profit to the wise? In this case, we will make an LED chaser based off a simple IC 555 timer and an IC 4017 decade counter. The circuit is extremely simple: the 555 timer gives a set pulse output dependent on resistors and a capacitor (or two, if you’re feeling fancy); which in turn activates specific pins in sequence on the IC 4017 chip.

Below is a schematic that I “procured” on the internet (Here is the site of origin).

Additional things you might want to know:

You may be more inclined to know how 555 timers work so here is a calculator

Also available on our resources page along with the full printable schematic


Here are the parts you will need

  • IC 555 timer
  • IC 4017 decade counter
  • 2X 1.5k resistors
  • 10X LED's of your choice
  • 100K variable resistor (A single turn carbon potentiometer, ACP VS5 was my choice.)
  • 3v coin cell holder (and a battery to match)
  • 1uF capacitor (electrolytic or ceramic capacitors should work perfectly fine.)
  • 10uF capacitor
  • A switch, to taste (This time around I wanted to use a slider switch)
  • As well as everything from part 1and part 2(Hey, no-one said this was going to be easy.)
  • And some perseverance



Tools

  • A Dremel
  • Small drill bits
  • Soldering iron
  • solder
  • Tweezer or small pliers: small pieces are a pain to handle (especially in areas of the board where space is limited)
  • Not required but always helpfull: A helping hand or clamp to hold the board while you solder

Once you get past the nitty-gritty of the printing and etching, all that's left to do is some continuity checks and then drilling holes. Be sure to have small drill bits on hand for this part, as well as solder, a solder-iron and workspace (duh).


It’s highly recommended that you don’t test the water with both feet: build the circuit on a breadboard first to get a feeling for space and to check if everything is working.

First up is making the circuit for printing. If you’re as lazy as I am you can always build it using perf board if the LED chaser part is all you are after; but in this case I want to incorporate the design as a pseudo business card for our website, as well as a gift for that special someone. So a hop, skip and download later, EAGLE Cad is open and ready to use (but seriously, the learning curve on this program is ridiculous. If you’re new to it, here are the videos that showed me how to use it: special thanks to Jeremy Blum). To start, make a new folder and a new schematic within said folder.

Ok; so far, so good. Now, open the components menu and…Wait, what are the component names again?

So it turns out that the manufacturer names are going to mess around with you some, but there are ways around that. Searching “decade” should bring up the 40xx series, which is the correct prefix. Alas, no 4017 seems to exist. At this point you may be feeling some dismay at you current situation, but fear not!There are varied definitions for the IC board because of its wide range of uses, but because it’s a CMOS logic drive it’s found in the subsection of counters and dividers. So it stands to reason that searching for either a counter or divider will bring up the 4000 CMOS logic drives that you need. Of course this is for EAGLE Cad,in any other fabrication software this may vary slightly. Now the resistors: EAGLE gives you the choice of either EU or US symbols, neither of which makes any difference to the end result, because they both use the same package resistor. Now for the trimpots, which are nowhere to be seen.

*Sigh.* Time for some coffee.

Now, depending on your particular item set you may have a trimpot (variable resistor) on hand that fits the description, but in my case I’m using a horizontal mounted resistor( ASP VS5), because I want a knob to control the flicker rate of the LEDs. Now comes scrounging around for what you need. In my case, EAGLE cad did not have the exact patent I am using, which means that you need to find one that’s close enough not to cause you problems when mounting. In this instance the saving grace was the RTRIM74X, which has pin dimensions similar *enough* to use or not, this was a problem that had to be resolved in part 2 to save you some effort we have the custom footprint for both the variable resistor and coin cell holder available on our resources page.

The coin cell I used was the B2430UNI. I got a little confused, but a brief Google search revealed this to be the component I needed. The E2-5 standard electrolytic configuration fits perfectly. Last are the 10 LEDs which are listed as 3mm, red tinted diffused LEDs (with TLLR 4400 as the Cadsoft ID).

And with that, all the pieces are done, and it only took two years!

It was right about this point when I realized that having the schematic drawn up beforehand would have been a wise decision to make. It saves alot of time when you can go out and buy components that do the same thing and are a little less obscure; which lets you just connect the points, setting you up for the next stage.