DMX only works if I touch it?

[tsfischer]

My son and I implemented the circuit from the example https://tigoe.github.io/DMX-Examples/arduinodmx.html.

However, something very strange is happening: The circuit only works if someone physically touches the wire from A5 to the MAX chip! For the longest time we thought it was a loose connection and were diagnosing how that could be... but sure enough, we find if we touch this wire... even the insulated portion, things work, and if not, DMX is dropped and our light goes into its own "color cycle" mode.

Now clearly the human body is acting as some sort of filter here... but I don't know enough about electronics to know what I should add to the circuit to make things work properly. Thoughts would be appreciated.

[tigoe]

Sounds like you have a grounding issue there. Can't sam more without seeing the physical circuit, but my guess is that something is improperly grounded and your body's providing the grounding.