Changes between Version 4 and Version 5 of ControlSystems/Electrical/Training/Arduino/Lesson5

Timestamp:

Oct 13, 2015, 9:27:52 AM (10 years ago)

Author:

David Albert

Comment:

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ControlSystems/Electrical/Training/Arduino/Lesson5

@@ -9 +9 @@
 When you build your mini-bot, you will mount an ultrasonic sensor on the front to help it navigate.  You can scan the environment in front of the robot by periodically having the robot turn on its axis while range finding; this will let it build a map of what's in front of it (Thanks to Ed Garner for that method!).  Other robot designs often mount the ultrasonic module [http://www.instructables.com/id/Arduino-HC-SR04-Ultrasonic-Rover/ on a servo motor] that continuously scans the area in front of the robot
 
-Potential problems: The ultrasonic sensor transmits a burst of ultrasonic sound and then listens for the echo.  The echo is received by a transducer that converts sound energy to electrical energy.  The further away the target is, the weaker the received signal will be.  To accurately measure longer distances, the sensor must be able to measure the very small voltages generated by the reflected signal and if the power supply to the sensor is fluctuating rapidly (we call that a noisy supply line) it is tough to do that (sort of like trying to hear someone whispering at a loud concert).  You can reduce the noise on the power supply lines by adding a decoupling capacitor: a small capacitor placed between +5v and Gnd as close to the ultrasonic sensor as possible.  For more information on power supply decoupling, see [DecouplingCapacitor here].  NOTE: you should use a non-polarized ceramic capacitor, however if you use an aluminum electrolytic capacitor (ask a mentor), you must observe the correct polarity, connecting the - lead to ground and the other lead to +5v...otherwise, the capacitor will turn into a firecracker.
+Potential problems: The ultrasonic sensor transmits a burst of ultrasonic sound and then listens for the echo.  The echo is received by a transducer that converts sound energy to electrical energy.  The further away the target is, the weaker the received signal.  To accurately measure long distances, the sensor must be able to measure the very small voltages generated by the reflected signal and if the power supply to the sensor is fluctuating rapidly (a noisy supply line) it is tough to do (try making fine measurements while bouncing on a trampoline).  You can reduce noise on the power supply lines by adding a decoupling capacitor: a small capacitor placed between +5v and Gnd as close to the ultrasonic sensor as possible.  The capacitor serves as a reservoir that absorbs spikes in supply voltage and supplies current when the supply voltage dips.  For more information on power supply decoupling, see [DecouplingCapacitor here].  NOTE: some capacitors are polarized (ask a mentor if you are not sure), if you are using a polarized capacitor, you ==must== connect the '-' lead to ground and the other lead to +5v...otherwise, the capacitor will turn into a firecracker.
 
 **Exercise**: Use your arduino to trigger the ultrasonic module and convert the resulting pulse duration into a distance; change the blink rate of your LED based on the distance to the target (faster=closer).