Ossiliscope is a vital take a look at and measurement system that allows us to investigate AC and DC indicators, visualize waves, and decide frequency.
Nonetheless, most conventional oscilloscopes are cumbersome and enormous in dimension, which will be inconvenient when working with microelectronics, designing, and testing small elements.
Subsequently, we’ve designed InduScope, a transportable oscilloscope that gives IoT connectivity, permitting customers to attach it to sensible TVs, laptops, and telephones. This allows real-time knowledge visualization, show enlargement, and wi-fi management of the oscilloscope.
Within the design course of, we utilized the IndusBoard Coin, which contains each DAC and ADC capabilities, enabling us to learn indicators and use the board as an oscilloscope. Moreover, a circuit was built-in to increase the oscilloscope’s vary.
The mandatory elements are listed under.
Invoice of Supplies
| Parts | Amount |
| IndusBoard Coin | 1 |
| BNC Connector | 1 |
| Slide change | 2 |
| Resistors 10K, 100K | 2 |
| IN4148 Diode | 2 |
| Capacitor 1uF | 1 |
IndusScope Circuit
Right here, the InduBoard ADC pin is used when connecting many multichannel oscilloscopes.
Nonetheless, to maintain the design easy and simple to fabricate, just one channel oscilloscope is made, and any pins can be utilized as an ADC. On this case, the four-pin is used as the primary channel of the oscilloscope.
After getting ready the code, we will instantly join the pin 4 to the probe to see the sign and use it as an oscilloscope. Nonetheless, to modify between AC/DC indicators and prolong the vary from 0 to 33V DC and 220V AC, we want a particular form of circuit.
Right here is the design and circuit wanted to attain this:
The voltage divider circuit consisting of R1 = 100kΩ and R2 = 10kΩ ensures secure enter voltage ranges for the ESP32-S2 ADC pin by cutting down the enter sign. The output voltage is given by:
Vout=Vin×(R2/(R1+R2))
=Vin×(10k/(100k+10k))
≈Vin×0.091
This implies the enter sign is decreased to about 9.1% of its unique amplitude, making certain it stays throughout the secure voltage vary of the ADC (0–3.3V).
Including a Capacitor for AC Coupling
To measure AC indicators whereas blocking any DC element, a collection capacitor is added. The capacitor ought to be positioned between the BNC enter sign line and the voltage divider (R1).
Steps to Add the Capacitor:
- Disconnect the connection between Pin 1 of BNC1 and R1.
- Insert the capacitor in collection between these factors.
Capacitor Choice:
- Low-frequency indicators (50Hz–1kHz): Use a 1µF to 10µF electrolytic capacitor.
- Excessive-frequency indicators (10kHz+): Use a 0.1µF to 1µF ceramic capacitor.
If utilizing an electrolytic capacitor, guarantee correct polarity—the constructive leg connects to the enter sign, and the damaging leg connects to R1.
Including Diodes for Overvoltage Safety
To guard the ESP32 ADC pin from voltage spikes, two clamping diodes are added on the output of the voltage divider (R2).
Placement:
- Join one diode between the ADC pin and three.3V (anode to ADC pin, cathode to three.3V).
- Join the second diode between the ADC pin and GND (cathode to ADC pin, anode to GND).
How It Works:
- Voltages > 3.3V are redirected to three.3V.
- Voltages < 0V are redirected to GND.
Really useful Diodes:
- Schottky diodes (e.g., 1N5819): Low ahead voltage drop.
- Normal diodes (e.g., 1N4148): Different choice.
Including a Slide Swap for AC/DC Mode Choice
A slide change (SW1) permits toggling between AC and DC coupling by bypassing the collection capacitor.
Tips on how to Join the Swap:
- Place the change in parallel with the capacitor.
- Swap closed: Capacitor is bypassed, enabling DC sign measurement.
- Swap open: Capacitor blocks DC elements, enabling AC sign measurement.
Why Add These Parts?
- Capacitor: Allows AC/DC sign measurement flexibility.
- Diodes: Defend the ESP32 ADC pin from voltage spikes.
- Swap: Permits fast switching between AC and DC coupling modes.
IndusScope Coding
The IndusScope oscilloscope code is designed to pattern enter indicators through the ADC, course of the info, and show real-time waveforms on an internet interface hosted by the ESP32-S2.
It begins by together with important libraries like WiFi.h for WiFi performance and ESPAsyncWebServer.h to arrange an asynchronous net server.
The ADC pin is outlined as GPIO4, and the reference voltage for the ADC is about to three.3V. The ESP32-S2 operates as an Entry Level (AP) with the SSID Indus-Oscilloscope and password 12345678, permitting units to attach instantly and entry the interface through the IP handle http://192.168.4.1.
The net interface is created utilizing HTML, CSS, and JavaScript. It encompasses a canvas for real-time waveform show, sliders to regulate time and voltage scales, and a “Capture Waveform” button to save lots of waveforms as pictures in a grid.
The drawGrid operate renders the oscilloscope grid traces, whereas the fetchData operate periodically retrieves sign knowledge from the ESP32 utilizing an HTTP GET request to the /knowledge endpoint.
The waveform is plotted on the canvas in actual time by the updateGraph operate.
The sign knowledge is processed within the handleDataRequest operate. The ESP32 collects 100 ADC samples at 100µs intervals, calculates the height voltage (most amplitude), common voltage (imply worth), and frequency (based mostly on zero-crossings of the waveform).
This knowledge, together with the sampled waveform, is formatted right into a JSON response and despatched to the net interface. Customers can regulate time and voltage divisions utilizing the sliders, and captured waveforms are displayed within the seize grid for additional evaluation.
This setup transforms the ESP32-S2 right into a compact, versatile oscilloscope with a user-friendly net interface.
Testing IndusScope
- Energy the oscilloscope and hook up with Indus-Oscilloscope utilizing the given credentials.
- Open a browser and navigate to http://192.168.4.1.
- Observe the real-time waveform, regulate settings, and use the seize grid to save lots of waveforms.
