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Activity #2: protecting the underside of your microcontroller
Book - Chapter 3

Notice with the Arduino UNO that the board has open wires on the underside. You must insulate those wires from accidental shorting or you may blow out your microprocessor. You can use rubber feet as below or some plastic insulator. Be very careful when prototyping on the board in association with the breadboard that you do not accidentally connect small wires with the underside or the upper side of this board.

The back of your board may not look exactly like this with the logos though the exposed wired are the issue to be resolved before you go on to read voltages.


You can place the rubber feet on the undersides of boards.

Here you can find a detailed PINOUT of the Arduino UNO R3. Notice on this page that one pin can source and sink 40 mA and 20 mA is recommended. The sum total of Miliamps for a series of pins is 100 mA. so for driving many LEDs, you should consider ohms law here and for the complete board no more than 200 mA. These are absolution Maximum ratings...never to be exceeded.


Place rubber feet under the board. Remember to wash your hands after touching any lead on the board.


We will be using the Arduino to practice measuring more DC voltages, and we will be exploring a breadboard as well.

If you are using the BS2 to not yet place your Basic Stamp chip on the board as well will be taking measurements from the socket on the board that the Basic Stamp will fit into.


Board of Education without the stamp.

NOTE! For now, leave the Basic Stamp 2 chip out of the Board of Education.


Parts Required

(1) DC multimeter
(1) Arduino or BS2
(1) Red wire
(1) Black wire

Introducing a Bread board

The white bread board (below) is a highly flexible prototyping and the testing area which can be integrated with microprocessors with connection wires.


White prototyping area. The valley between the rows can except chips and electrically isolate the pinouts from each side of the board.


Probing the Board with our Multimeter

Now plug your Arduino programming cable into the board or your Stamp transformer into the wall and plug it into the Board of Education.

Use connector cables to place wire coming from the 5V and Gnd sections of your Arduino UNO or other Arduino product to test and measure Voltages. Notice that the Arduino also have a 3.3 Volt output pin.

Measure that now. 

Notice on the Arduino that the LED will glow green indicating it is on.

Turn on the basic stamp carefully and do not to allow any unshielded wire or metal to touch the metal contacts or traces on the underside of the board.


Notice that you can choose to use a plug or battery. For the purposes of this lesson, the transformer is advised, though not necessary, if you want to use a 9-volt battery instead

Take the red connector wire and lay it in the black header called VDD, and take a black wire and lay it in the black header called VSS. Allow them to stick straight up, as shown below.

  1. Set your meter to the 20-volt DC setting.
  2. Wedge the red probe so it is touching the wire and lightly pushed into the socket that the wire is nestled into. Do the same for the black on the black wire.

    Measuring DC with multimeter


  1. What is your voltage reading on the multimeter? ________________
  2. Reverse your red and black multimeter probes so the metal tip of the red probe touches the metal of the black wire and the tip of the black probe touches the metal of the red wire.
  3. What voltage do you read? _______________________
  4. Do you notice a – minus sign in front of your voltage reading?

    Measuring DC with multimeter

  1. Why do you get this voltage? _________________________
  2. Could it be because you have switched your probes so the red which is normally used for the + side of the voltage source is now reading the – side of the voltage source?______________________