Change the Resistance

Did You Know: Load or No Load?

In the main activity, you measured the I/O pin high voltage under load.
In the Try This section, you measured the I/O pin high voltage with no load.
In both activities the I/O pin low voltage was not under load because it was trying to supply 0 V to a circuit that had 0 V (GND) at the other end.  No electrical pressure was applied, so no current was flowing through the circuit.  Thus, no current “load” on the I/O pin.

Your Turn: Change the Resistor Value

• Try replacing the 220 Ω resistor with a 1 kΩ (brown-black-red-gold) resistor.  
• Repeat the high and low signal I/O pin voltage measurements.  

What I/O pin voltage under load did you observe?  What is your explanation?  

• Make sure to put the 220 Ω resistor back before moving to the next activity.