Telepresence-Robot-Distance-Sensor.pdf

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Telepresence Robot: Distance Sensor
by randofo
Most of the sensors we have investigated so far
involve navigating immediate dangers, such as things
the robot crashes into or sudden drops. The distance
sensor takes a different approach in sensing things
far away so the robot can make informed decisions
about what to do next.
The particular sensor we are using is a PING
distance sensor. This sensor uses ultrasonic sound to
calculate the distance of objects in space. It works on
a similar principal to the edge detection sensor in that
it sends out a signal -- in this case an ultrasonic
sound and not LED light -- and then measures how
long it takes to bounce back. By calculating how long
it takes to return in relation to the speed of sound, we
can calculate how far away the object is that the
sound bounced off of.
This sensor works up to about 12 feet, and allows you
to measure with reasonable accuracy the distance of
objects over a wide area. This is not only helpful in
avoiding things, but can also be used to get a basic
sense of the shape of the environment. With the right
code, it can even be used as a crude motion sensor.
However, we are primarily using it to avoid objects.
This sensor is meant to prevent the collision switches
from being triggered. The collision switches are
intended to be more of a fail-safe and last resort than
effective means of interacting with the world. The
distance sensor is being installed to keep the robot
from crashing in the first place.
This is the fifth part of a seven-part instructables
series. Over the next two instructables we will be
building the basic electromechanical robot platform.
This platform will later be enhanced with sensors and
additional control electronics.
To learn more about the topics covered in this series
of projects check out the Robot Class, Electronics
Class, and Arduino Class.
Telepresence Robot: Distance Sensor: Page 1
Step 1: Materials
You will only need one thing for this lesson:
(x1) PING ultrasonic distance sensor
Telepresence Robot: Distance Sensor: Page 2
Step 2: Test It Out
Plug the sensor into a breadboard and wire its pins to the Arduino as follows:
Ping 5V to Arduino 5V
Ping Ground to Arduino ground
Ping Signal to Arduino digital pin 4
The Ping sensor "talks" to the Arduino by sending a series of rapid high (5v) and low (ground) pulses to the digital
input pin. The Arduino is able to interpret these special pulses and calculate the distance of objects. It is a bit like
someone is communicating with the Arduino in morse code by tapping on a switch that is connected to the input
pin, except it is happening really - really - really - fast.
High and low pulses is the basis of all digital communication and logic. When people talk about computers running
on 1s and 0s, this is what they are referring to.
Once the wires are connected, upload the following code and open the Serial Monitor:
Telepresence Robot: Distance Sensor: Page 3
Step 3: Mark and Drill
Place the sensor on the front of the plastic box and mark it's mounting holes onto the box.
Also make markings on the box just next to the each of the board's mounting holes. We need these second holes
to zip tie the sensor to the box.
Drill all of these marks with an 1/8" drill bit.
Telepresence Robot: Distance Sensor: Page 4
Step 4: Solder Wires
We're going to need to solder 12" solid core wires to
each of the pins on the sensor.
To make this easier, we are going to first tin the pins
on the sensor and each of the wires. What tinning
means is to melt a little bit of solder onto a surface to
prepare it to be soldered later. We do this because
solder likes to stick to other solder. If both surfaces
already have solder on them, it will make them easier
to join.
Once everything is tinned, solder the green wire to
SIG, the red wire to 5V and the black wire to GND.
Telepresence Robot: Distance Sensor: Page 5

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