Level 1Project 2 · Session 32
32

Project 2 · Build 1 of 2

Wire it, one part at a time

Today: the circuit, proven piece by piece. Not the whole thing at once.

The rule for today

One part. Test it. Then the next part.

It is tempting to wire everything and then run it. Everybody wants to. It also means that when nothing happens, you have six things it could be, and you will spend the session guessing.

  1. Wire one component. Just one.
  2. Write the smallest program that proves it is alive — blink the LED, print the sensor, move the servo a little.
  3. Run it. Does that one part work?
  4. Only when it does, add the next part. Test again.
  5. Repeat until everything on your list is wired and proven.
💡 Tip
Keep every little test program. When the big one misbehaves next session, you can go back to the small one that definitely worked and find out what changed.

The four rules of the bench

  • Power off while you wire. Build it, check it, then plug in.
  • Black to black. Ground wires are black, every time, on every project. It makes mistakes visible.
  • Push the wires all the way in. Half-in is the single most common fault in this room.
  • Check before you power on. Two people look at it. It takes ten seconds.
What you seeWhyWhat to do
Nothing at all happensPower, or the board is not connected.Is the light on the board on? Is the USB in at both ends?
It worked and now it does notA wire moved when you added the last part.Go back to the last thing you changed. It is nearly always that.
The LED is very dimWrong resistor, or wired backwards.The long leg goes to the plus side.
The sensor number never changesWrong pin, or a loose wire.Print the number and watch it while you wiggle each wire.
Everything resets randomlyThe servo is drawing too much from the board.Servos need their own power. Ask your teacher.

Before you pack away

  • Every part is wired and each one has been proven on its own.
  • Your little test programs are saved in your Robotics folder.
  • Nothing is half-wired. Either it is done or it is out.
  • Everything back in the bin, checked against the card.
Challenge optional — only if you finish early
  • Make your circuit work on a battery instead of the laptop.
31. Choose, and plan