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Topics Covered

  • connectivity on the breadboard
  • polarity of the power supply, positive and negative voltages.
  • proper practice for cutting wires and stripping the ends of wires. how to use your wire clippers and your wire strippers.
  • how to use your multimeter to measure continuity, voltage.


  • wire clippers
  • wire strippers
  • 12V DC 500 mA power supply/AC Adapter. (do you have any of these at home? In case you burn one out, it may come in handy. check your old scanner, phone charger, etc., they are all labelled with voltage, current, polarity).
  • solderless breadboard
  • black and red hookup wire.
  • black and red alligator cables.


Distribute the kits. Please keep them in the lab, with the understanding that once you have paid for them with Judi you can take them home. (We will have the final price in next week, please bring a check addressed to the UC Regents).

Breadboard Setup and Voltage Supply:

  • Connect the positive and negative rails running along the top and bottom of the breadboard. The positive rails have a red bar running next to them and are labeled with a "+", the negative rails have a blue bar running next to them and are labelled with a "-". Use a short red wire to connect the positive rails and short black wire to connect the negative rails. Make your wires long enough to avoid blocking any of the holes on the breadboard, but not so long that they are trailing off into space. See the picture below.

Breadboard w supply.jpg

  • Set up your multimeter: attach the red and black probes and remove the covers over the tips.
  • Test the continuity setting of the multimeter. Turn the dial to the position in the photo below, and make sure the black probe is connected to the middle socket and the red probe is connected to the far right socket. Keeping the probes apart, the screen should display "1" on the far right. When you touch the two probes, it should beep. This setting lets you know if two points in a circuit are connected without power running through the circuit.

Continuity setting.jpg

  • Use the continuity setting on your multimeter to check that you successfully connected the positive and negative rails in step 1.
    • Are your red supply holes connected at every point on the board?
    • How about the black ones?
    • You are making sure that your power is distributed properly for later use.

Power continuity check.jpg

  • Clip the end of the power adapter off, saving enough wire with the plug to reconnect the two later in the semester (do not clip the wires too close to the plug).
    • Cut the two loose ends to different lengths, to prevent accidentally touching them together.
    • Separate the two wires and strip the loose ends of each.
    • Twist the end of each wire to join the loose strands together.

Clipped plug.jpg Assymetrically clipped.jpg

  • With the DC voltage setting on the multimeter in the appropriate range, identify which is the positive and which is the negative wire coming from the adapter. The voltage setting on the multimeter dial is shown below. The number at top will display the current voltage. It is helpful to use a red and black alligator cable to connect from the multimeter probes to the power supply. Attach them as shown. WARNING: You need to plug the adapter into the wall. Be sure that you do not touch the two power supply wires together, this will short out your power supply and you will be out $5.00. This is your first live voltage!

Voltage setting.jpg Pos neg alligator clips.jpg Testing powersupply voltage.jpg

    • What is the voltage you record?
    • Which is the positive wire and which is the negative wire?
    • Is the positive wire labeled in any way?
    • Attach the red alligator cable to the positive wire, and the black alligator cable to the negative wire. This is the standard color code for positive and negative, red for "+" and black for "-". We will use this throughout the course.
  • Unplug the power supply.
  • Using one red and one black alligator cable and a short length of red and black hookup wire, connect the positive and negative lines from the power supply to the appropriate power buses on the breadboard.

Power connected.jpg

  • Plug the power supply back in.
  • Measure the voltage across the positive and negative power bus. Measure it at a number of different points on the board.
    • What is the voltage that you see?
    • Is it the same at every point on the board?

Measuring power bus.jpg

  • Unplug your power adapter from the wall, and look at the label on the back.
    • What is the labeled output value?
    • Is this different from the voltage you measured before?