Introduction
In the October 2016 issue of SERVO, we built the
Parallax ELEV-8 v3 kit and began to explore its capabilities.
The ELEV-8 has since made appearances as an instrument
platform for a meteorology package and has other projects
planned. One of the first things I wanted to add was the
capability to send vehicle data back to the ground.
Before we go any farther, I must stress that as the
pilot, your first priority is safe operation of the aircraft, but
having your spotter glancing at a screen full of vehicle data
could be very valuable if you lose your orientation or would
like an altitude check. Recording the telemetry data could
be useful when performing a post-crash analysis, or trying
to measure and improve the vehicle performance.
This month, I’ll walk you through the process of adding
the ELEV-8 900 MHz Telemetry Kit (Figure 1)
(
https://www.parallax.com/product/32480) and go
through the troubleshooting that occurred when things
didn’t work on the first (or second) try. While this article is
specifically about using the kit and software from Parallax,
the telemetry system is based on XBee radio modules, so
there’s something to learn here no matter what kind of
multi-rotor or radio system you
choose to use.
XBee
Introduction
XBee is a series of modules
from Digi that lets you easily
make connected devices in
everything from a complex
mesh network to a simple
“wireless serial port” type
configuration. They use the IEEE
802.15.4 networking protocol,
and are a really nice and
inexpensive way to add a
wireless component to many
projects. If you want to learn
more about using wireless
protocols and peripherals in your project, check out the
book, Building Wireless Sensor Networks by Robert Faludi
(
http://amzn.to/2eJ6FMl).
The radios used here are the 900 MHz models. This is
important as the radio system we are using to control the
quad is a 2. 4 GHz system. Using multiple 2. 4 GHz systems
on the same quad would likely result is lots of interference
and possibly losing control of the vehicle.
I have had no previous experience with the XBee
products other than reading articles about projects that had
used them in Nuts & Volts and SERVO. This was a good
chance to dive in and learn a little bit about how they work.
I’m thinking that they could be an even simpler solution
than Wi-Fi for sending data
from sensor packages down to
the ground, but they are slightly
more expensive. The kit that
we’ll install this month retails
for $149. The Pro 900HP
modules that we’re using sell
for $39 individually.
XBee
Configuration
We need to set up the
parameters the XBee radios will
use to communicate. Digi
The
Multi-Rotor
Hobbyist
Adding Telemetry
to the ELEV-8
By John Leeman
Post comments on this section and find any
associated files and/or downloads at
www.servomagazine.com/
index.php/magazine/article/
January2017_MultiRotorHobbyist_Telemetry.
8 SERVO 01.2017
Pilots of regular aircraft have a panel of
instruments that indicate important parameters
such as the aircraft altitude, air speed, attitude,
and engine system status. As multi-rotor pilots,
we are often operating by look and feel. We can
estimate our altitude through experience and
the aircraft attitude through the use of colored
propellers or motor struts. This month, we are
going to add a telemetry kit to the ELEV-8 v3 to
get real time aircraft data sent back to our tablet
in the field.
Figure 1: The complete telemetry kit from
Parallax includes two XBee radios, antenna,
USB adapter, USB cable, zip ties, header, and
RPSMA extension cable.
