Arduino Lego Tannerin

Step 4 The schematic

The circuit schematic. You will want to replace the resister with some large enough to limit the current through the nichrome wire (lest it gets too hot), but small enough so there's a noticeable drop in potential when the marker short circuits part of the wire. The Arduino has a 0-1023 range for a 0-5v on its analog inputs. i.e. 5 mv per input entry. So if you want 100 possible inputs along the wire, there must be 0.5v across the nichrome wire.