6. Electronics Design¶
This week’s group assignment was to learn how to use test equipment in our lab to observe the operation of a microcontroller circuit board. (As a minimum, we should demonstrate the use of a multimeter and oscilloscope)
Definitions of technical words covered in class:
| Equipment | Description | Useful for | Tutorial (Rico’s recommendation) |
|---|---|---|---|
| Regulated Power Supply | Provides a steady voltage to a device, regardless of changes in the input voltage | Testing electronic circuits and other devices (because they provide a stable voltage) | |
| Multimeter | Measures electrical values like Voltage(AC, DC), Resistance, Capacitance, Continuity in one unit | To confirm that circuits and devices are safe and working properly. | Youtube |
| Oscilloscope | Graphically displays varying voltages of one or several input signals as a function of time | Identifying the problem in a circuit, determining if a component has malfunctioned, identifying the shape of a wave, comparing several inputs graphically, etc. | Youtube |
| Logic Analyzer | Captures and displays multiple digital signals from a circuit or system | For examining the behavior of digital signals over time, by analyzing the timing and logic states of various signals simultaneously. | Youtube |
| Mixed signal | Can simultaneously analyze and test both analog and digital signals within a circuit | For testing integrated circuits (ICs) that contain both analog and digital components |
Using the Multimeter¶
Multimeter allows us to measures electrical values like Voltage(AC, DC), Resistance, Capacitance, Continuity in one unit. It’s useful for confirming that circuits and devices are safe and working properly.
This is the multimeter we used for our test;
1. Measuring the Voltage¶
This test is useful for checking if the voltage at different points in the circuit is within the expected range; this can helps us confirm if a power source is providing the correct voltage, checking for potential problems in wiring/connections, if a switch is properly switching voltage, etc. The Multimeter can test for either AC Current and DC Current. You can distinguish them with these symbols;
Most of the time we will be measuring a DC, and under 20 V.
Steps:
1. Turn on the Multimeter.
2. Turn the knob on the Multimeter to select AC or DC, and maximum voltage of the power source you want to measure. This time, we tested DC voltage of <20V
3. Touch the probes to Negative and Positive poles of the device
Remember!
First, touch the Black probe to Ground (negative) pole
Then touch the Red probe to Positive pole
We compared the voltage of different power sources;
From a working battry; we got 8.9V
From a dead battery; we only got 1.2V
We also tested the ESP32 Dev Kit. From the 3.3V output pin, we got 3.2V.
2. Measuring the Resistance¶
This test is useful for determining the Resistance value of a Resistor.
On Resistors, there are no positive and negative poles, so you just touch the 2 ends with the probes. We start with turning the knob to the biggest measurement, and adjust the knob to move down to the unit that is appropriate.
The resistor we measured was 220 Ohms.
3. Testing the Continuity¶
Testing for Continuity means to testing the circuit to determine if it’s closed or open. This test will be useful for determining if my sodder joint is good. Or to test that a LED is not broken.
- Turn the knob to select the Diode mark.
- Touch the 2 ends of the circuit you want to test.
4. Testing the Current¶
Thi is useful for determining if a circuit is functioning as expected. For exaxmple, measuring the current at different points can help pinpoint which component is malfunctioning. Measuring the current draw of a battery can also provide insight into its remaining capacity and lifespan. We can also verify circuit design calculations, by comparing measured content to theoretical calculations.
We tested a simple LED blinkig circuit;
1. Remember, you first need to break (open) the circuit in order to test it.
2. Touch the 2 ends of the circuit (to close it).
We measured 5.4mA.
5. Testing the Capacitance¶
What is Capacitance??? Should we know about this too??
Using the Oscilloscope¶
Oscilloscope allows us to observe parameters such as frequency, amplitude, and waveform shape, as a function of time. This help understand how voltage and current change across the circuit (the waveform) and verify if a device is correctly sending or receiving data. This helps with identifying issues like timing errors, signal integrity problems, noise, and other anomalies in a circuit, enabling us to pinpoint the source of malfunctions and make necessary adjustments to the design.
For our test, we used the Hantek DSO5072P (Link to PDF Manual);
On the screen is displayed a graph of Voltage vs Time.
1. Set up¶
Turn on the machine and select settings such as AC.
2. Connect to the circuit¶
We made a blinking LED circuit (blink every 100 milli seconds), and attached the positive probe to the circuit and negative probe to the Ground.
3. Calibrate and Read¶
At first, the scale is usually too big, so we need to calibrate the machine by touching the probe, and adjusting the dials.
One calibrated, we could read the square-wave pattern of blinking LED.
We changed the blinking speed to LOW=500 milli seconds, HIGH=100 milli seconds to observe the change in waveform shape.
We also tested Serial Communication.
We tested the current flow by the program of showing letter K by Xiao.
“K“‘s ascii code is “111101011”.
First number is start bit(0) and end bit(1) and we have to read the number from back.
However, since both of these are a LED On/Off circuits, in theory these tests could also have been done using a Logic Analyser.