Build a Logic Probe

Logic Probe
Another useful tool for electronics debugging is the logic probe. A logic probe will tell you the logic of a particular point in a circuit, and whether the point has low or high voltage. We start the prototype circuit on the breadboard before soldering the circuit onto a printed circuit board.

 When the probe is powered and not testing for logic or voltage.

 When the probe touches the positive side, the LED glows even brighter.

 When the probe touches ground, the LED goes dark.

Now that we have enough practice, we move onto the fabrication lab for some surface mounting work. This requires a tedious soldering job because once a mistake is made it will be difficult to fix the mistake (I only have one PCB!). After the soldering is complete, we take an exacto knife to make the incisions necessary for this particular circuit because the PCB is made in such a way that all the pins are intertwined as one circuitry. So, our logic must thoroughly predetermined before we begin cutting.

Once we finish our board should function as it did in the breadboard and we put a little bit of hot glue to prevent any of the components from moving about the pins and short-circuiting.

 

DB9 Serial Connector
To prepare for programming and interfacing between a microcontroller and the PC, we solder the necessary wires onto a DB9 serial connector.

The wiring should look as such and shrink wrap should be used to prevent unintended wires from shorting.