Week 8 Reading Inputs, Pull Up and pull down resistors, ADC

 What are Pull Up and Down resistors / Reading high low voltages with the pico

  • What are they
  • Experiment to show why the are needed
  • Pico comes with them built in.  (But I could not get them to work)


ADC

  • What voltage drop is expected across a 1000 + 10000 voltage divider. Experiment
    This setup using a voltage divider is required for ADC work
    Equation to work out Vout
    Vdrop = R1/(R1+R2) * Vtotal
    Vdrop = 1000/(1000+10000) * 3.3
    Vdrop = 0.3 V
    The voltage measured after the 1000Ohm resistor would be 3.3Ohm - 0.3Ohm. = 3.0 Ohm
    If we put the 10000 Ohm resistor as R1 it would drop the voltage by 3V so the measurement would be 0.3V


  • GPIO 26, 27,28 are the only ADC pins
  • Experiment with potentiometer


  • Experiment with light dependent resistor



Powering the Pico from an external source

  • Power via usb powerbank
  • Connect pins. Using between 1.8 and 5.5 V 
    • Steps to Power Externally
      1. Connect a suitable power source such as a battery pack (e.g., three AA batteries, or a single-cell LiPo battery) or a benchtop power supply.
      2. Identify the VSYS and ground pins on the Pico.
      3. Connect the positive (+) terminal of your external power supply to the VSYS pin on the Pico.
      4. Connect the negative (-) or ground (GND) terminal of your external power supply to one of the Pico's ground pins.
      5. Do not connect the Micro USB and VSYS power at the same time unless using a diode for protection. This can cause damage to your battery or Pico. 
      6. Taken from Core Electronics Video
  • What is the "main" program
 

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