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