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This tutorial summarizes the methods used by Waterloo Labs engineers to wirelessly monitor and control their car.
Method
In the Waterloo Labs “Drive a Car with an iPhone” Video the engineers used a wireless configuration of a National Instruments Compact RIO and a National Instruments Wireless DAQ device monitor to control various components in the car. This combination allows them to drive the car anywhere without being tethered to a wired network. Because this hardware was used in a car, no wired AC power supplies were available. All devices in this video were battery powered. This document will provide an overview of how the engineers set up their wireless system to monitor and control the car.
The engineers placed optical encoders on the wheels of the toy car and read in voltage values from the encoders. They also connected a potentiometer to the steering wheel and measured the resistance of the potentiometer to measure steering wheel position. The outputs of the optical encoder and potentiometer were passed to the input of an NI WLS-9215 Wireless DAQ card, and the data from the 9215 was sent to a laptop using a standard wireless G router. The engineers then used LabVIEW to process the data and convert it to useful information such as speed and direction.
Figure 1. The wireless setup of the car. The router is on the left,
battery on the right, and the CompactRIO is in the center.
The laptop was then connected to an NI cRIO-9072 controller, and the data was passed from the laptop to the cRIO. The data was used to set desired speed and steering angle for the car using LabVIEW Real-Time. The calculated values for the desired speed and steering angle were then used to control the motors connected to the gas pedal and steering wheel using NI 9201 and NI 9403 modules installed in the cRIO chassis.
Related Links
Products and Services: NI CompactRIO
Products and Services: NI Wireless DAQ
Developer Zone: NI Wi-Fi DAQ Overview
KnowledgeBase 3NOKD7FQ: Connecting a CompactRIO Controller to a Wireless Network
KnowledgeBase 4K68J5LX: How Much Power Do I Need to Have in a Battery to Power my CompactRIO?
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