Oscilloscopes are used to graphically display time varying signals, with time as the independent variable on the x-axis, and the dependent variable, such as voltage or current, on the y-axis. They are incredibly useful, but bench top scopes can be large and bulky, and break the bank at the same time. The Analog Discover 2 aims to alleviate both problems, being at once affordable as well as compact and lightweight.
For this Instructable you will need:
- 1X 100μF electrolytic capacitor
- 1X 20kΩ
- 1X 9V battery w/ battery clip
- 1X breadboard w/ jumper wires
-Waveforms 2015 software*
- a computer with USB port to run the software
*You may also use the original Analog Discovery or the Electronics Explorer Board with Waveforms 2015. There are some slight differences in functionality between the AD1, AD2, and EEBoard, but nothing that will prevent you from following along if you have one of the other tools.
There isn't much background to oscilloscopes, so let's just dive right in. If you want some help with AD2 calibration and Waveforms installation/setup, check out this quick start I'ble collection.
Before we get to using the AD2, we need a simple time-dependent circuit so we can see what's going on.
When the switch is closed, the capacitor charges but quickly reaches full capacity. Once it does, it acts like an open break in the wire and the voltage across the resistor is the same voltage as the battery. Once the switch opens, the capacitor starts to drain through the resistor. The equation Τ = RC tells us that it will take Τ (Greek Tau) seconds for the capacitor to drain to ~36.8% of it's previous value. For our schematic, we get Τ = 20kΩ * 100μF = 2s. We'll come back to this value in a bit.
Connect the 30-pin connector to the AD2. Connect "1+" to the capacitor anode (+) and connect "1-" to the capacitor cathode (-). Because the oscilloscope channels on the AD2 are fully differential, meaning that they can measure differences in potential between the "1+" and "1-" pins with no need for a GND reference, there is no need to connect a GND wire from the AD2, though you may if you wish. If you use the Electronics Explorer Board, the scope channels are not differential so you will need to connect one channel to the anode and GND to the cathode. In this example that also connects to the "-" battery terminal.
Your circuit should look something like this once you have it all set up.
Once you have your AD2 and circuit set up, open Waveforms and click on the "Scope" button at the top.
The Oscilloscope window will open.