I don't know what a busy board is*, but I made some sort of LED light board for my nephew and niece years ago. It's a wooden box just a bit bigger than a sheet of paper. The top of the box has 4 columns of nails planted in, nail head on top. The bottom of each nail in the two left columns connect to a specific nail in the two right columns.

The idea is to print a sheet of paper with questions on the left, and answers on the right. For instance, colored squares on the left next to each nail, and the actual name of the color near the nails on the right. You put the sheet of paper over the nails, the sheet if of course already punched over each nail, and you pull 2 pins from the box, they are cabled to a battery and a green LED so that when you close the loop by pressing one pin on the question nail and the other pin on the correct answer, the LED will light up. You can print several sheets with the same questions but in a different order, or reverse the questions and answers, like putting the names of the colors on the left and the colored rectangles on the right.

Keep the questions and answers interesting so that even if the kids memorize the correct nail combinations after a while, they are more interested by the novelty of the questions than by cheating with the memorized positions. One set I liked most had the names of the animals and the sound they make. 18 months is a bit young for such a word board though, you'd need pictures. The upper inside part of the box has the battery and cabling, the bottom part can be used to store all the question and answer sheets.

You can probably replace the battery with a potato and tin/copper electrodes or electric play dough to make things even funnier. Of course, that was long before the days of the iPad... ;)

* Oh, I see the picture now, never mind! Pretty cool "busy board."

(Electric play dough.jpg)

Electric play dough.jpg (12KB - 26 downloads)