33. Make it do the thing, then test it on a stranger

Project 2 · Build 2 of 2

Make it do the thing, then test it on a stranger

What we are making: the finished thing — and then, in the same session, finding out what it looks like to somebody who did not build it.

First half: make it work

Do not touch the wiring from last session. It works. Leave it alone.
Get the output doing its thing on its own, with no sensor involved.
Join them with one decision. Usually three lines.
Make it happen ten times in a row and count how many times it does the right thing. Ten out of ten, or it is not finished.

💡 Tip

If it works on the third try but not the first two, it is not working. Something is marginal — nearly always a threshold too close to the normal reading, or a wire barely making contact. Find out which now. It will not fix itself before the exhibition.

Second half: the stranger

Swap with another team. Put your thing in front of them and say nothing at all. Watch. Write down every time they pause, touch the wrong part, or ask what it does.

Swap. Say nothing. Write down what you see.
Swap back and read your list.
Fix the three worst things.
Add a label: what it is, and what to do to it.
Then stop. No new ideas after today.

💡 Tip

‘They just did not get it’ is not allowed as an answer. If a person cannot tell what your thing wants them to do, that is a fact about your thing. A label, or a light that shows it is ready, fixes most of it in five minutes.

What you see	Why	What to do
The output never fires when the sensor should trigger it	The join, not the halves.	Print the reading and the decision together. One of them is wrong and you will see which.
It fires all the time	The comparison is the wrong way round.	Swap the > for a <, or move your number.
It worked last session and not now	A wire moved in the tray.	Check what you carried, not what you coded.
The stranger pressed it twice	Nothing told them it had worked.	Something on the device has to change when it does.

Before you leave

Your thing working ten times out of ten.
Your observation list, and the three fixes made.
A label on it.
Everything packed against the bin card. Nothing half-built left out.

Challenge optional — only if you finish early

Give somebody your machine with no label and watch. Then add the label.

32. Wire it, one part at a time