After months of waiting I can now finally continue my series of posts on making a multitouch table. The reason for this delay was suspiciously long shipping times for some additional equipment (I will talk about this in the next post).

In this post I will describe how we have connected IR LED diodes together and what problems we had on the way. There are a few photos of our wiring in my gallery. The first idea was to use 20 diodes wired in parallel. This gave us a system with peak voltage of 1.8 V (determined by a single diode) and very high current requirements (some 6 A). As non-electricians we did not realize that this may be a problem, we just wanted to have the wiring as simple as possible. Combined with a very weak power adapter (used to power some simple devices such as CD players and such) it naturally did not work … as the power adapter can usually produce less than 1 A of current.

Next time we actually researched the topic a bit and decided to make the system bigger in every way. We increased the diode count to 80, add some small resistors and wire them in 8/10 sequential/parallel system (schematic representation shown on an image below). This system has peak voltage of 14.4 V and requires about 4 A of current to function.

At the beginning we thought that an off-the-shelf camera adapter could power that thing … no luck. With visible signs of desperation we borrowed a tunable PSU station and plugged the system to the maximum safe configuration. Still no real progress. At that time we decided that the problem has to be somewhere else and decided to change the camera. I can now say that the camera was indeed the weak link and that the system now works very well … even to well in some cases. I will talk about our camera issues in the next post.