LEGO Circuit Boards
Crazy Circuits (crazycircuits.com) has introduced a line of electronic components that fit onto LEGO mounting. As in the photo above, you can build an electronic circuit onto a LEGO baseplate using conductive tape (instead of wires) to join components. Decorative lighting is a useful application for this design, and Crazy Circuits has several types of LEDs built onto chips. They also sell blank chips that you can solder your own components onto, as in the photo below, where I put a color-changing LED and a resistor onto chips.<
While the circuit connection with tape works well, I also found a convenient solution in soldering blank Crazy Circuits chips onto LEGO electric plates. A chip before soldering is shown in the photo below. The soldering wasn't easy and tended to burn the plastic of the LEGO plate, so a conductive epoxy might be a better alternative. The blank Crazy Circuits in this design for the photo at the top of the page has two wire leads attached to it, so the plate can be used to make a connection to vintage 9V and Power Functions parts. This is an excellent alternative to my previous approach of cutting up vintage cables.
Another use for Crazy Circuits I found was to step down the voltage from a 9V supply using a voltage regulator. Many such regulators, such as the 2950 and 780x chips, have three leads that conveniently fit into a Crazy Circuits header chip. In the photo below I have a 2950 regulator to supply 3.3V for powering LEDs. If you need a 5V supply, you can just swap out the regulator.