Automatic Weightlifting Spotter

Mid Semester PresentationSenior Design I

February 27, 2014

Team Members

Chris ChildersElectrical

Engineering

Nathan CarrollElectrical

Engineering

Garrett DoorenbosElectrical

EngineeringTeam Leader

Drew BosargeElectrical

Engineering

Faculty Advisor

Dr. Robert Reese

Professor

ECE Department

Outline• Problem

• Solution

• System Overview

• Constraints

❖ Technical

❖ Practical

● Approach

● Progress (Timeline)

● Questions/Comments

Problem

• When lifting free-weights, a spotter must be present to ensure the safety of the lifter.

• When a spotter is unavailable, weightlifters are likely to lift without one, exposing themselves to injury and possibly death.

• From the years 1999-2003:o 1-4 deaths annually involved asphyxiation from neck compressiono As many as 3,820 injuries per year may be related to bench press

failures[1]

Solution

A microcontroller-based system that will use sensors and a motor to allow users to lift

weights safely without a spotter:

The Automatic Weightlifting Spotter

System Overview

• Sensors determine position, speed, and direction of barbell

• Microcontroller reads sensors and sends directions to motor

• Motor lifts the barbell as instructed by the microcontroller

Technical ConstraintsName Description

Detection of Bar The device must detect the position, speed, and direction of the bar.

Weight Limits The Automatic Weightlifting Spotter must be able to handle weights ranging from 45 pounds to 405 pounds.

Reaction Time The product must have a reaction time that is fast enough to protect the user from falling weight.

Notifications The Automatic Weightlifting Spotter must implement a user interface to indicate the status of the machine to the user.

Power Requirements The device must run on 120 VAC power.

Practical Constraints

Type Description

Health and Safety

Fail-safes must be implemented to prevent possible injuries to the user.

Usability The product should not be used by beginners and must come with an owner’s manual.

Approach

MotorPros Cons

DC Winch ● Simple process to control speed.

● Could use car battery for power.

● Would have to heatsink 30A.

● Car battery would have to be charged frequently.

AC Winch ● Already variable speed.

● Plug into wall outlet for power.

● More complicated speed control.

[3]

[2]

Microcontroller

[4]

[5]

IO pins Price

Arduino Mega

54 $58.95

dsPIC33 21 ~$2

User Display

Pros Cons

Seven Segment Display ● Easy to use ● Not able to display much info

LCD Display ● A lot of info can be displayed

● Many IO pins are required

Laptop Interface ● Easiest to create● No extra hardware

required

● Not practical for weightlifting environments

Weight Sensor

Pros Cons

Tension sensor Direct measurement of weight

Has to be inline with the tension cable, hard to find

Pressure sensor Can lay in rack while the weight is stationary

Requires extra hardware and software calculations to work

Supporting Frame

[6]

Cost

Build frame from scratch using wood ~$8 for 4”x4”x8’ board

Build frame from scratch using Steel ~$120 for 4”x4”x8’ bar

Purchase Power Cage to act as frame ~$350

Barbell Attachment

• Hole in bar with cable hookup

to machine

• Tow straps attached to each end of bar

• Use eye clamps on each end of the bar

[9]

[8]

[7]

Wheel EncodersPros Cons

LED encoder Easier to implement and debug

Light can cause interference

Hall-Effect encoder Light not an issue Harder to debug

[10] [11]

Progress: TimelineJanuary February March April

Research, Documentation, and Analysis

Order parts

Build frame

Implement user display

Design Software

Implement Sensors

Testing

Finalize & Present Design

References[1] V. Patteson Lombardi, “Petition Requesting Labeling of Weightlifting Bench-Press Benches to Reduce or Prevent Deaths Due to Asphyxia/Anoxia,” unpublished.

[2] http://www.globalindustrial.com/p/material-handling/dock-truck/winches/warn-1700-dc-powered-

1700-pound-capacity-12v-utility-w. Feb. 26, 2014.

[3] http://www.globalindustrial.com/p/material-handling/dock-truck/winches/warn-works-pullzall-

handheld-110v-ac-electric-portable-pulling-li-ing-tool

[4]http://arduino.cc/en/uploads/Main/ArduinoMega.jpg. Feb. 26, 2014.

[5]http://www.electropages.com/2013/02/farnell-element14-ideal-prototyping-popular-16-bit-dsc-family-expanded-dip-packages/. Feb. 26, 2014.

[6]http://dldiscountfit.com/racks/power. Feb. 26 2014.

[7]http://totalgymcare.com.au/sales/images/uploads/Snap_Hook_Final.JPG. Feb. 26, 2014.

[8]http://simage1.sportsmansguide.com/adimgs/l/1/140756_ts.jpg. Feb. 26, 2014.

[9]http://www.bhphotovideo.com/bnh/controller/home?O=&sku=690061&Q=&is=REG&A=details. Feb. 26, 2014.

[10] https://www.sparkfun.com/products/241. Feb. 27, 2014.

[11] https://www.sparkfun.com/products/9312. Feb. 27, 2014.

Automatic Weightlifting Spotter

Mid Semester PresentationSenior Design I

February 27, 2014