Electromagnetic Bodybuilder
ECE 445 | Spring 2016 Project Proposal TA: ​
Jackson Lenz Project Contributors: Harrison Kim | hjkim6 Michael Liu | mliu41 1 1.
Introduction 1.1.
1.2.
1.3.
Title:​
Electromagnetic Body­Building We decided on this idea because we recognized some of the problems with the benchpress system that could be solved by using electromagnetic force. We are excited to work on this project because it is something that has not been done before, and will have practical use. Motivation:​
There are several components in a free weight bench press systems that could be improved. First, having to constantly replace weights on the bar and organizing them are tedious actions in the bench press process. Secondly, bench pressing can be dangerous, without a reliable spotter. Lastly, buying sets of weights that can only increment by 5 lbs at a item can be very costly. We believe that our electromagnetic bench pressing system will be able to overcome these inconveniences. Objectives & Benefits:​
The goal of this project is to replicate and bench press systems using electromagnetic force with easy to use controls for the user. Some benefits of an electromagnetic bodybuilding system include: ● Eliminates the tedious process of switching weights ● Organizing the weights is no longer needed with the control system ● A spotter will not be needed with the safety control ● The amount of force will be able to be changed more precisely than current free weights ● Having to buy sets of weights is no longer necessary ● Will maintain relatively same amount of force in places with lower gravity 2.
Design 2.1.
Block Diagram Figure 1 depicts the block diagram for the electromagnetic bodybuilding mechanism. Figure 1:​
Block Diagram 2 2.2.
3.
Block Descriptions 2.2.1.
Power Supply The power supply module will be the main source of voltage for the system. The power will come from a standard 120V ± 5% outlet which will be supplied to the variac. 2.2.2.
Control System 2.2.2.1.
Variac The variac will be the control unit of the system that will allow a user to change the voltage across the wire of the electromagnet. As the voltage of the variac changes, the current will change with a direct relationship, thus increasing the magnetic force the solenoid produces. 2.2.2.2.
AC­DC Converter The AC­DC converter will be used to convert the AC power from the low side of the variac. An AC­DC converter is necessary because an electromagnet using AC current will have a magnetic field that is constantly reversing directions, whereas a one using DC current will have a constant magnetic field. A constant magnetic field will be required to keep the weight simulation consistent. 2.2.3.
Electromagnet (solenoid) The electromagnets are the meat of the system. There will be two solenoids that will produce the magnetic field necessary to replicate the weight. 2.2.4.
Emergency Cutoff The emergency cutoff switch is the safety module of the system. This will be a foot switch which will allow the user to cut off the power to the electromagnets in case of an emergency. Requirements and Verification Table 1: ​
Requirements and Verification Requirement Verification Power Supply 1. V​
= 120 V ± 6 V out​
Power Supply 1. Variac 1. 0 VAC < V​
< 120 VAC out​
2. 0 AAC < I​
< 100 AAC out​
Variac 1. Connect variac to wall outlet 2. Attach oscilloscope to variac output terminals (both voltage and current probes) 3. Turn variac on with knob at 0 V and measure V and I. Verify within low range. 4. Turn variac knob slowly to 120 V and measure V and I. Verify within high range. Points 0 10 3 AC­DC Converter 1. 0 VAC < V​
< 120 VAC in​
2. 0 VDC < V​
< 120 VDC out​
3. 0 AAC < I​
< 100 AAC in​
4. 0 ADC < I​
< 100 ADC out​
AC­DC Converter 1. Turn variac off and connect AC terminals of converter to variac. 2. Connect oscilloscope and multimeter to DC end of converter. 3. Turn variac on at 0 V. Measure voltage and current at DC terminals of converter. Verify within range. 4. Turn variac slowly to 120 V and measure voltage and current at DC terminals of converter. Verify within range. 15 Electromagnet (solenoid) 1. I​
= 100ADC ± 10 ADC max ​
at 12V 2. Length 7­10ft Electromagnet (solenoid) 1. Measure temperature as current is increased. Observe to see that the max temperature rating of wire (200​
°) is never reached when stepping to 100A 2. Perform verification 1 with different length of wire. 15 Emergency Cutoff Switch 1. Rated I​
= 100 ADC ± max​
10 ADC 2. Rated V​
= 120 VDC ± max​
10 VDC Emergency Cutoff Switch 1. With AC terminal of converter connected to variac, connect switch to DC terminal of converter. 2. Connect oscilloscope to other end of switch. 3. Apply rated voltage to circuit and measure V and I. Verify within range. 4. Flip switch and ensure voltage and current are cut off. 10 4.
Tolerance Analysis One of the most important components required in our project is the solenoid. It must be able to withstand the current and heat that it is sustaining. Magnetic wire are graded by the temperature that they are able to withstand. To calculate the amount of temperature that will be reached by the wire, we would have to determine the rate at which heat is added and find where it is equal to the rate is it being removed, the latter being more difficult to find. Since this requires testing to estimate, we compared it to other projects of similar capacity of around 90​
±50% C. 50% tolerance is sufficient for temperature because most magnetic wires are rated to withstand 200 degrees C or above and we are only concerned with the upper limit. This tolerance range will be well under the 200 degrees rating. We also suspect a maximum ampacity of the wire to be around 100A. Therefore we expect a wire that can sustain a current of 90±10% A. We got this value assuming that we will be using a max voltage of 12V, and based on the American Wire Gauge standards, a 10 gauge wire will suffice at these specifications. We set a tolerance of 10% so that it will not exceed 100A. Wire gauge specifications are set assuming 20,000hours of life at max rating. 4 5.
Cost and Schedule 5.1.
Cost Analysis Table 2: ​
Labor Wage Hours Total Michael $40/hr 180 $18,00 Harrison $40/hr 180 $18,000 Total $80/hr 360 $36,000 Table 3: ​
Parts No. Part Cost 1 14AWG Copper Magnet Wire $25 2 4 Rods $60 3 Bench Press and Bar $75 4 Power Supply $150 5 Variac $75 6 Emergency Foot Switch $15 7 Various Wires and Components for controls from ECE store ~$20 8 Power Tools ~$100 Total $520 Table 4: ​
Grand Total Labor Parts Costs Grand Total $36,000 $520 $35,480 5 5.2.
Schedule Table 5: ​
Schedule Week Task Delegation 2/8 Finish Proposal Talk with Professors Harrison Kim Finish Proposal Talk with Professors Michael Liu Find and Order Parts Prepare mock­up Harrison Kim Draw general design Prepare mock­up Michael Liu Test limits of ordered parts Document limits for solenoid wire Prepare design review Michael Liu Check if ordered parts operate as expected Order additional parts if necessary Calculate different EM forces desired Prepare design review Harrison Kim Start to construct solenoids Check interactions between solenoid and variac with voltage supply Michael Liu Start to construct solenoids Formulate safe testing method Measure force ranges achieved Harrison Kim Solder solenoid and wire for stability Test interaction between solenoid and bar Harrison Kim Design solenoid configuration in bench press towers Michael Liu 2/15 2/22 2/29 3/7 3/14 Append the benchpress system to house the solenoids Harrison Kim using power tools and attach solenoids Append the benchpress system to house the solenoids Michael Liu using power tools and attach solenoids 3/21 Spring Break 3/28 Design Control Switch mechanism with foot pedal. Incorporate footpedal emergency switch Michael Liu 6 4/4 4/11 4/18 4/25 5/2 Design display for force/pounds relationship Create display for force/pound relationship Harrison Kim Testing and Debugging Prepare for mock demo Michael Liu Testing and Debugging Prepare for mock demo Harrison Kim Optimize Product Michael Liu Optimize Product Harrison Kim Fix any remaining issues. Michael Liu Fix any remaining issues. Harrison Kim Final Presentation and Demo Michael Liu Final Presentation and Demo Harrison Kim Final Presentation and Demo Michael Liu Final Presentation and Demo Harrison Kim 7