Week 08: Electronics Design

Assignment

• Use the test equipment in your lab to observe the operation of a microcontroller circuit board (as a minimum, you should demonstrate the use of a multimeter and oscilloscope)

Using Multimeter

A multimeter is an essential tool for measuring electrical values such as voltage, current, and resistance.

Let’s cover the basics. Here’s parts of Multimeter

• Display: Shows the measured value.
• Selection Knob: Allows you to set the multimeter to measure voltage (V symbol with ~ for AC and — for DC), current (A/mA), resistance (Ω), capacitance (mF, nF, µF), continuity, etc.
• Ports: Where you plug in the test leads. In our multimeter, this includes:
  • COM (Common): The ground or negative input
  • VΩCap: For measuring voltage, resistance, and Capacitance.
  • mAmF : For measurin small currents.
  • 10A: For measuring larger currents.

Measuring Voltage (DC)

• Set the selection knob to the DC voltage setting (symbol: usually ‘V’ and a straight line and/or a dashed line beneath it).
• Plug the black lead into the COM port and the red lead into the port marked for voltage (VΩCap)
• Touch the black probe to the negative side of the component/circuit and the red probe to the positive side
• Read the voltage on the display.

Testing GND plane Voltage = ~5V

Testing VIN track Voltage = ~3.3V

Measuring Resistance (Ω)

• Set the selection knob to the resistance (Ω symbol)
• Same as before, - Plug the black lead into the COM port and the red lead into the port marked for voltage (VΩCap)
• Touch the probes to either end of the component.
• Read the resistance on the display.

Testing 1k Ohm Resistor

Measuring Capacitance

• Ensure that the circuit is not powered. Discharge the capacitor completely before measuring it to avoid damaging the multimeter. We did this only by touching the capacitor with our finger.
• Turn the selection knob to the capacitance mode, marked with a symbol that looks like two parallel lines (representing a capacitor) or “F” for farads
• Touch the probes to either end of the capacitor.
• Read the capacitance on display. The multimeter display will show the capacitance value in farads (F), microfarads (µF), nanofarads (nF), or picofarads (pF).

Testing 10 nF Capacitor

Measuring Voltage (AC)

• Set the selection knob to the AC voltage setting (symbol: ‘V’ and a wavy ~ line).
• Plug the black lead into the COM port. And plug the red lead into the port marked for voltage.
• Touch the probes to the two points in the circuit where you want to measure the voltage.
• Read the voltage on the display.

Testing Continuity

• Turn the selection knob to the continuity test mode.
• Insert the black lead into the COM port and the red lead into the port marked for continuity or resistance
• Touch the positive and negative probes to the two points you want to test for continuity.
• Listen for the Beep: If there is continuity, means there is an electrical flow (a complete connected path), the multimeter will beep. If there is no beep, it means there is no continuity (the circuit is open).

Using Oscilloscope

An oscilloscope is an essential tool in electronics for visualizing electrical signals. It shows the signal’s voltage over time, allowing for the analysis of parameters such as frequency, amplitude, and waveform shape. By displaying waveforms in electrical circuits, oscilloscopes help understand how voltage and current change across the circuit and verify if a device is correctly sending or receiving data.

While standard multimeters can display voltage or current values, they are too slow to capture rapid changes and present them meaningfully.

MiniWare DS13 Oscilloscope

For this assignment, we’re going to use the MiniWare DS213 Oscilloscope.

The MiniWare DS213 Oscilloscope comes with a set of two probes, ground clips, and identification rings.

It features 4 input channels, 1 waveform output channel, micro USB port, and a power button.

There are 2 scrollers and 4 buttons for function and navigation. We will use mostly scroller B to navigate the menus around the screen and scroller A to adjust/change different values.

For a complete guides on how to operate this Oscilloscope, please refer to this DS13 Mini Oscilloscope User Manual.

Workflow: Probing Device (Rotary Encoder) with Oscilloscope

Physical Setup

1. Turn on the Oscilloscope

2. Attach the probe(s) to the channel input. Connect the probe tip to the intended measured point on the circuit.

   In this case, we’re testing Rotary Encoder. So, we will hook two probes to CLK and DT pins of the Rotary Encoder;

   

3. Attach the ground clips to the circuit ground;

   

   This is how the overall physical setup looks like:

   

Now that the physical setup is complete, if we rotate the Rotary Encoder, it will generate some visuals on the oscilloscope.

However, these visuals still appear as straight lines and are not yet meaningful to us. So we have to adjust the settings.

Signal Display Adjustment

1. Before reading, make sure the settings for Channel A and Channel B is in “AUTO” mode and “DC” coupling.

2. Adjust the (horizontal) time scale to an appropriate value to view several cycles of the waveform. This changes the time span displayed on the screen. We set it to 500 mS.

3. Adjust the (vertical) voltage scale to a suitable value to display the signal clearly. We set it to 2V/div.

4. Adjust “Vtrg” (the trigger level) so the signal is stable on the screen. Typically, set it to the midpoint of the signal amplitude.

5. You can also select measuring data, such as Vpp (peak-to-peak voltage), Vavg (average voltage), FRQ (frequency), etc.

Observing the sine wave

Clockwise Rotation: the blue signal line rises first

Counter-clockwise Rotation: the green signal line rises first

Rapid Rotation: