Medieval Madness glowing castle skulls mod!

This page will attempt to show how I went about modifying my Medieval Madness pinball machine to have glowing red skull eyes. The skulls on the original castle are not painted so they really blend right into the surrounding castle. I painted my castle to have a totally different look and one of the changes was to paint them white with dark shadows for aging. But, even though they stood out, they still needed something more. I had seen on the Internet where someone had installed tiny LEDs into the eyes of the skulls so I decided to do the same on mine. There are really no defacto instructions on how to do this. Therefore, I designed my own version.
Here we have the unmodified Castle. The skulls have been painted by myself previously as mentioned above. However, the skulls have not been drilled nor fitted with LEDs.
I used this Lexan to determine the correct drill bit size to use to get the optimum sized hole to accept the LEDs, yet hold them securely in place.
I can't really tell you what size drill bit I finally used because it was not stamped on the drill bit. It turned out to be a fairly tiny drill bit but to give it some scale, I took a picture of it next to a ruler.
I test-fit an LED in one of the holes to see if it would be snug. It fit well and wedged itself in. I will also secure them with hot glue later in the project.
Here is another picture showing the LED from the front side as it pokes through. This would be similar to the LED sticking out from the skull's eye sockets.

This schematic is the creation of Ed Cheung. Ed is an extremely smart pinhead that works for NASA. He designed this circuit and this is the one that I used for the skulls as well as the LEDs I put under the catapult plastic. It is wired in parallel so that when one half-cycle of the AC waveform is on, one LED is on, and on the second half of the waveform, the other LED goes on (while the first turns off). Due to the frequency of the LEDs turning on and off (60 times per second), our eyes cannot tell that the lights are actually turning on and off. Thanks to Ed for this circuit and please visit his site http://www.edcheung.com/

Here is a picture of a completed set of LEDs for the skull. By following the above circuit, you can see how to build it. Basically, the positive portion of the A/C cycle voltage comes in through pin 1, travels through R1, through D1 and back to ground. On the negative portion of the A/C cycle, voltage will flow from pin 1, travel through R1, then go through D2 and back to ground. I didn't use Ed's complete circuit, just the theory on how to hook the LEDs together to utilize both portions of the A/C wave. That way, there is always one LED on instead of if they were in parallel, both would be off and both would be on during the A/C cycle.
Here you see both sets of skull LED assemblies built. If you are familiar with the resistor color code, you will notice that I used 470ohm resistors as the current limiting resistors in the circuit. I didn't want the LEDs to be too bright so I used a fairly large sized resistor. The smaller the value, the brighter the LED will be. Don't go too small or you will burn the LEDs out or at the least, shorten their life.
I took a picture of the final assembly. Here I put heat-shrink tubing on to keep the legs of the LEDs from shorting once they were put in the castle.
This picture is a little difficult to see, but this is a picture of the LEDs inserted into the holes I drilled in the skull's eyes on the right side of the castle. When I drilled out the eyes, I angled the hole upward so that you can see the LEDs better. The skulls are looking slightly downward. Therefore, you have to compensate for that while drilling.
This is a shot of the LEDs test-fitted into the left side of the castle.
I have both assemblies installed into the castle. They are not secured yet, just being test-fitted. I will be bending the leads in and behind the main archway section where I will attach wires to connect both sides together for power.
To secure the LEDs into the castle, I didn't want to use screws etc, so I raided my daughter's room and took her craft hot-glue gun. This thing worked extremely well. The hot glue holds very well, is solid, yet it can be taken off if needed without damage to the castle.
Here you can see where I glued in the LED. I used quite a bit to ensure there was no movement of the assembly. I didn't want my LEDs falling out or tipping up or down, after I had them in the game.

Once the LEDs were installed and glued, I bent the leads inside the castle and pointed them towards the center. I soldered on some extension wires that were used to connect the left LED assembly to the right for shared power. In this picture, you can see where I put a blob of hot glue on the wires to hold them in place. Great stuff that hot glue!!
Here I show a better view of how the wires from the left (top portion of the picture), connect from the left LED assembly to the right. Then, I took two wires from my hard drive ribbon cable and soldered them to the positive and negative leads of the right-side LED assembly. Since they are connected to the left side assembly, both will now have power once connected to the game's G.I. A/C circuit. Also in this picture, you can see how I again used hot glue to attach the wires to the castle. You can also see the flickering tower modification circuit board also attached with hot glue, in the bottom portion of the picture.
I took a shot of the finished installation of the LEDs in the skull's eyes. They are not lit in this picture. This is the left side of the castle.
This is the right side of the castle. The skulls are not both oriented exactly the same. I believe the right side skull is looking in a more downward position so I had to work with the LEDs to ensure they didn't point downward.
Early on, I tested the skull LEDs before I glued them in. Since they are going to be attached to a GI circuit, when testing with the 5v DC source, only one side will light at a time.
I rigged the assembly to have power on both sides to ensure they both worked. Here you can see a pic of the test. The camera has a hard time taking pictures of LEDs for some reason. I think the wavelength of the LEDs is hard to capture on the camera's CCD without looking oversaturated.
Here are the connectors I made. I used .156 connectors and headers. The female end comes from the castle for both the flickering tower mod and the skull eyes mod. The skulls will be connected to the GI circuit while the flickering tower mod was connected to a 5v DC location on the power driver board.
This is a close-up shot of the skull connector. I labeled the connector and used my daughter's trusty glue gun to create a strain-relief on the wires. I soldered the wires onto the connector instead of stamping them in and displacing the wire. I wanted to be sure I had a solid connection.
My final pictures is rather hard to comprehend. It is a picture from under the playfield where I connected the wires to the GI circuit that was nearby the castle. On the other end of these wires, I put the .156 header pins. These connectors hung under the playfield awaiting me plugging them into the female connectors I have coming from the castle. That way, I can flip up the playfield and easily disconnect them if needed. I guess I don't have a picture of the connectors connected under the playfield. But, I think you get the idea. Female connectors on the castle side connect to the male header pins connected to the GI circuit.

I hope this was detailed enough to allow you to at least see how I made the mod for my skulls on Medieval Madness. Hopefully this how-to page will inspire you to modify your castle and perhaps design something new!

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