Post on 22-Dec-2015
The WeedRake
By Nick Bigelow, Matt Merrit, Tyrel Ellis and Jason Pemberton
Background
Weed removal is a labor intensive, time consuming part of owning a garden
Some gardeners use herbicides to shorten and simplify the process
Herbicides are harmful to the environment The stalks are 12” apart with a roughly 4”
diameter of roots that can not be damaged Corn stalks are at least 5” tall
Problem Statement
We need to find a way to use MARV to remove weeds automatically without the help of human hands
Solution
We are going to use a rake assembly to remove the weeds
We are using ultrasonic sensors for plant detection and navigation of the WeedRake
System Overview Diagram
Flow Chart
PING))) Sensor Specs
Range: 2cm to 3 m Supply Voltage: 5V Supply Current: 30mA Input Trigger: 5us typ. Echo pulse: 115us min to 18.5ms max
Sensor Diagram
HC12
Rake Mechanism
Lifting Mechanism
State Diagram
Torque Calculations
It will take about 30 inch pounds to push the rake assembly out
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Motor Specifications
We are using the DENSO DC gear motors for moving the rake mechanism
These motors operate at 12 volts and have a no load current of 1.5A
The motors turn at 162 RPMs
Motor Controller
Calculating Motor Travel
13 threads per in 6 inches horizontal travel 162 RPM 1 rev = 1 thread 13 TPI x 6 Inches = 78 threads 78 threads / 162RPM = .48 minutes .48 minutes = 28 seconds
MARV Speed
Max Speed is 3.9 mph Uses 2 DENSO DC gear motors (12V,1.5 A,
162 RPM) 8 inch Diameter wheels We will limit MARV to a speed of 6 inches per
second 6 inches per second is 8.7% of MARV’s top
speed
Personal Assignments
Nick and Jason on the extension mechanism Tyrel and Matt on the lift mechanism Jason and Nick on programming MARV and
the motor controller board Tyrel and Matt built the rake mechanism
Budget
Cost Cost to Us
Two Motors $40.00 Borrowed
3 ft threaded rod $5.00 $5.00
Relays $6.86 Borrowed
Rake $8.00 Donated
1" square stock $5.86 Donated
1.5" square stock $9.60 Donated
Total $75.32 $5.00
ScheduleWeek 1 Week 2 Week 3 Week 4 Week 5 Week 6
Brainstorm/Choose GroupsGroup Meeting: Concept IdeasGarden TripTest SensorsCalculate Motor RequirementsDraw Concept DiagramsChoose MotorsGather Rake MaterialsCreate System DiagramCreate State DiagramCalculate Motor TravelBuild Rake MechanismDesign PresentationMount Rake MechanismWrite Microcontroller ProgramTest SystemTroubleshooting