Fun with LEDs
LEDs have been available to the pinball collector for quite a while now and I’ve been impressed with the results that can be achieved with them. I’ve also been disappointed at some of the things they don’t to too well like general illumination lighting. The biggest down side for me with LEDs has always been the cost so I decided to build some myself. The nice thing about building yourself is that you can customize the LED lamp for the specific effect you’re looking for.
The first step is to buy some LEDs. I found the “flat top” LEDs to work the best under inserts which is where I’ll be using most of my LEDs. Brightness is also important. I experimented with “super bright” LEDs of different intensities and found the general rule to be brighter is better. I bought my LEDs on ebay. I was able to get a bunch of different types from a manufacturer in China for a good price.
You’ll also need current limiting resistors. You’ll need to look at the specs for the LEDs you purchase and use a calculator to determine the resistance value you’ll need. For my experiments I used mostly resistors in the 100-200 ohm range.
The first step (once you’ve acquired the LEDs and resistors) is to prepare the LEDs to be installed in a #47 lamp socket. I cut one of the legs on the LED and soldered one leg of the resistor to it. The resistor is in series with the LED in the circuit to limit the amount of current that can flow through it.
Here is an example of an LED ready to install in a socket:
This picture shows a batch of super bright blue flat top LEDs ready for assembly. The flat top LEDs have a wider viewable light angle making them a better choice for pinball. LEDs with a narrow viewable light angle may not light up the whole insert and appear as a dot.
NOTE: LEDs are light emitting diodes. A diode will only allow current to flow in one direction. This means that the LED must be installed with the cathode to the negative side of the circuit and the anode to the positive side. In the machines I’m planning to use these LEDs in the negative side of the circuit is the small contact on the lamp base and the positive side is the lamp base frame. You will need to take this into consideration should you decide to make your own LEDs.
Once the LEDs are ready we need lamp bases to house them. I chose to salvage my lamp bases from burnt out #44 and #47 lamps. Fortunately I have a huge supply of these burnt out lamps. I did enquire about purchasing the bases from a couple of lamp manufacturers but wasn’t able to get anywhere.
I started by desoldering the old element from the lamp base. I tried drilling the hole and a couple of other methods but desoldering proved to be the best method. This picture shows the lamp bases before and after desoldering. The height difference is due to the fact that the desoldered lamp has also had it’s glass bulb removed.
The next step is to remove the glass bulb from the base. I found the best method to be gently squeezing the base where it meets the bulb with pliers. The bulb will break so you’ll want to contain the glass somehow. I break the bulbs with the pliers inside a large zip-lock bag to contain the glass. It’s not exactly delicate work. You just want to remove the bulb without bending the base too badly.
Here we see some bases ready for assembly.
I found it was easiest to solder the outside leg first.
Soldering the outside leg first allows you to position the LED before soldering the other leg. Once the LED is positioned where you want it you can solder the other leg.
This LED didn’t come as a flat top but I was able to sand down the dome on the LED later to widen the viewable light angle.
Once the LEDs cool from soldering I fill the base with hot glue.
This picture shows a bunch of double LED lamps. I’ve used as many as 4 LEDs in one base.
Here are the same LEDs after filling the bases with hot glue. Not the cleanest looking hot glue job but they work well.