Things Used In This Project
- Digilent Analog Discovery 2
- Servo (generic)
Software apps and online services:
- Digilent LabVIEW Home Bundle
- Everything from Setup (OpenScope, micro USB, wires)
- Breadboard (from Parts Kit)
- Servo (from Parts Kit)
- USB-B Cable
- Mini Grabbers
- Analog Discovery 2
Verifying Your Servo Signal
Connect your Servo to your Arduino using breadboard wires.
- Orange servo wire – Pin 9
- Red servo wire – Power 5V
- Black/Brown servo wire – GND
- The servo should be in SWEEP mode
- The Arduino implements a PWM signal, that is a square wave with a duty cycle that can range from 0% to 100%.
- We will use LabForms and the Analog Discovery 2, to see exactly how long the duty cycle is on, what voltage, and duration.
Connect the Analog Discovery 2 to the Arduino
- Disconnect the Servo
- Remember, the PWM Signal for the Servo is on Pin 9 of the Arduino.
- Use a breadboard wire, connect OSC1 (Orange Wire) to Pin 9.
- Close out LabForms, open up a new window (so the settings reset to default).
- Hit Run.
Grounding the Oscilloscope Channel
Anytime you use your Oscilloscope channel, you need to have a Ground connected.
Since the Arduino is on a different circuit, the Analog Discovery 2 needs to know its ground in order to correctly measure the signal. Let’s demonstrate this.
Plug a breadboard wire into the Analog Discovery 2 analog ground (orange or blue with white stripe) and plug it into one of the Arduino Ground Pins.
Adjust the signal on the screen
The Arduino puts out 5V signals. We suggest “zooming out” so you have the signal cleanly on your screen.
“Volts/” will allow you to change the Y Scale of the graph. Offset will allow you to move where 0 is.
It’s important to make sure that the screen is “focused” on the part of the waveform with the information we need.
For this exercise we are interested in what happens when the signal goes high, so the top of the waveform needs to be seen.
Change your Volts/ Division to 1.00 V and Offset to 1.5 V (you can scroll or type it in). You can also type in mV instead of V.
- Cursors are a way in which you can set points of interest on a screen, and display the exact value.
- LabForms allows you to put single cursors on Time or Voltage.
- Time – We’ll use this to see if the PWM signal has a consistent duty cycle
- Voltage – We’ll use this to see what Voltage the PWM signal peaks at.
Test our cursors
- Hit SINGLE to capture a single acquisition of the waveform
- Turn on Cursors, select Time
- Line the cursors up with the edges of the signal by moving the dotted lines at the top of the graph
- Pay attention to the calculations to the right of the cursors button
- Follow the same procedure for Voltage
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