Thrill ride enhancement: seat sensors




THRILL RIDE ENHANCEMENT: SEAT SENSORS


By


Rachel Adaniya

Kristin Jones

Jason Witek


ECE 445, SENIOR DESIGN PROJECT


SPRING 2005


TA: Mo Zhou


May 3, 2005


Project No. 6


ABSTRACT

The Thrill Ride Enhancement: Seat Sensor system is designed to enhance the safety features of theme park Thrill ride enhancement: seat sensors rides by providing an electronic means of checking occupant safety before ride dispatch. The system detects the occupancy and state of the seat belt of any seat on the ride vehicle Thrill ride enhancement: seat sensors, and reports the current state of the seat to the ride operator. It uses capacitance sensors to detect occupancy and Hall-effect sensors to detect the state of the seat belts. The system Thrill ride enhancement: seat sensors reports faults in the seat sensors and counts the number of guests passing through the ride.


The main goal of this project is to expand the safety features of a ride Thrill ride enhancement: seat sensors system by adding seat occupancy detection to the current seatbelt and vehicle control systems. This paper describes construction of the seat sensor system, including the design process, the finished design Thrill ride enhancement: seat sensors, verification results, and cost.


^ TABLE OF CONTENTS


1. INTRODUCTION 1

1.1 Purpose 1

1.2 List of Acronyms 1

1.3 Review and Update 1

1.4 Specifications 1

1.5 Subprojects 2


2. DESIGN PROCEDURE 3

2.1 Power 3

2.2 Seat Belt Sensors 3

2.3 Programmable Logic Controller (PLC) 3

2.4 Fault Signal 4

2.5 Seat Sensors 4

2.6 LED Display 5

^ 3. DESIGN Thrill ride enhancement: seat sensors DETAILS 6

3.1 Capacitance Seat Sensor 6

3.2 Magnetic Seat Belt Sensor 7

3.3 PCB Circuit Design 8

3.4 PLC Program 9

3.5 PLC and LED Display 13

3.6 Finished Seat Sensor System 15


4. DESIGN VERIFICATION 16

4.1 Seat Sensors 16

4.2 Seat Belt Sensors 16

4.3 PLC Control Signals 17

4.4 Power Conversions Thrill ride enhancement: seat sensors 17

4.5 Water Tolerance 18

4.6 Testing Conclusions` 18


5. COST 19

5.1 Parts 19

5.2 Labor 19

5.3 Total Cost 19


6. CONCLUSIONS 20


REFERENCES 21

1. INTRODUCTION

Walt Disney Imagineering proposed a seat sensor system as an added safety feature in two Disney ride systems Thrill ride enhancement: seat sensors, including Dinosaur in Disney’s Animal Kingdom and The Indiana Jones Adventure in Disneyland.


1.1 Purpose

Currently, ride operators must manually check the state of each seat and seat belt before the ride vehicle leaves the Thrill ride enhancement: seat sensors station to verify occupant safety. Thrill Ride Enhancement: Seat Sensors automatically detects the occupancy of each seat on the ride vehicle and the state of each seat belt. Adding the seat sensor Thrill ride enhancement: seat sensors system will eliminate the need for a manual safety check. The seat sensor system enhances safety features, reduces the time required for a manual safety check, and increases hourly ride capacity Thrill ride enhancement: seat sensors. The goal of the seat sensor system is to create a prototype that checks seat occupancy and seatbelt state at the load station, and convey this information via LED to ride Thrill ride enhancement: seat sensors operators so that a decision to dispatch a ride can be мейд.


^ 1.2 List of Acronyms

WDI Walt Disney Imagineering

PLC Programmable Logic Controller

PCB Printed Circuit Board

CPU Central Processing Unit

IC Integrated Circuit

EEPROM Electronically Erasable Programmable Read-Only Thrill ride enhancement: seat sensors Memory

EM Electro-Magnetic


^ 1.3 Review and Update

This system prototype was successfully built according to the specifications outlined in the proposal. It examines the occupancy of two seats and the state of two Thrill ride enhancement: seat sensors corresponding seat belts and then transmits that data to an LED display. A system fault signal detects problems in the system and reports them to the LED display. A seat counter was Thrill ride enhancement: seat sensors added to count the number of guests that frequent a seat on a given day. Counter results are displayed on the DV-1000 display on the PLC case. Sensor outputs are sent Thrill ride enhancement: seat sensors to a PLC to output the data on LED's, which indicate four states for each seat. This system involved the design and placement of sensors and electrodes on each seat to detect capacitance Thrill ride enhancement: seat sensors as well as sensors to indicate that the seat belt is buckled. The PLC program was written to interface all components, and the system was packaged to meet all specifications.


1.4 Specifications

The seat sensor Thrill ride enhancement: seat sensors system must be capable of monitoring the state of the seat sensors and seat belts. An LED indicator alerts the operators of the following states:

The seat sensor system must be an affordable safety enhancement with no additional attraction operators needed once device is installed. It must Thrill ride enhancement: seat sensors make use of off-the shelf parts whenever possible. It must be designed to function on or around the existing attraction vehicle with a minimal amount of additional equipment. It also must have Thrill ride enhancement: seat sensors the potential for system expansion, such as detecting seat occupancy and seat belt position while the ride is in motion. It must be 99.99% reliable, durable to withstand the physical stress of Thrill ride enhancement: seat sensors the ride, and be waterproof.


1.5 Subprojects

Control Logic and PLC

Seat Sensors
Vehicle Control System

Guest


Operator LED Display








Seat belt Sensors

PLC Display


Power Supply





^ Figure 1.5 Seat Sensor System Block Diagram

Figure 1.5 shows the seat sensor system Thrill ride enhancement: seat sensors block diagram. The seat sensors interact with the guest to detect the state of occupancy of each seat. Seat sensor design includes circuit design surrounding a QT310 capacitance chip, electrode selection, and Thrill ride enhancement: seat sensors calibration of seventeen parameters in the QT310’s onboard EEPROM. The power supply powers all components. The control logic and PLC takes sensor, fault and reset inputs for each seat and translates Thrill ride enhancement: seat sensors them into corresponding output states. The control logic must convert 24 VDC from the power supply to 5 VDC to supply the sensors, and then must raise all 5V sensor logic signals to 24V Thrill ride enhancement: seat sensors logic to properly trigger the PLC. The PLC software implements the state decoder, fault detection, and seat counters. The LED’s display four states for each seat, and the PLC display and the Thrill ride enhancement: seat sensors DV-1000 displays PLC status and seat counters respectively. In the design process, work was broken down according to the blocks in Figure 1.5.


^ 2. DESIGN PROCEDURE


The design procedure began by reviewing the design specifications provided Thrill ride enhancement: seat sensors by the Walt Disney Company as specified in section 1.4. Disney graciously supplied a PLC and accompanying software to implement the state decoder. Disney further suggested the use of Quantum QT310 chips for Thrill ride enhancement: seat sensors use in the seats to detect the capacitance of a person. With these considerations in mind, the design process began. The following sections describe design alternatives and decisions мейд for Thrill ride enhancement: seat sensors each system component.


2.1 Power:

To eliminate the need for additional equipment, the 24 V power supply packaged with the PLC was used to supply power to all components. 24 V is readily available on the ride vehicle Thrill ride enhancement: seat sensors so the seat sensor system need not use a supplementary supply. Originally the power conversions were designed for a 24V power supply, as the power supply used was specified to be Thrill ride enhancement: seat sensors 24 V as per the industry standard. In testing, the power supply was found to output 28V and recalculations were мейд to accommodate the higher voltage. The QT310 capacitance sensor, the MP Thrill ride enhancement: seat sensors1301 magnetic hall sensor, and the switch are rated at a maximum input voltage of 5 V each. This posed as a problem since only 28 V was available. A LM317 voltage regulator was used to Thrill ride enhancement: seat sensors drop 28 V to 4.87 V, creating a sensor power supply. To determine the output voltage of the voltage regulator, the following equations were used:


Vout = Vref(1+R2/Ra)+Iadj*R2 (1)


Iout Thrill ride enhancement: seat sensors = Vref/R1 + Iadj = 1.25/R1 (2)

Sensor outputs needed to be stepped up since the PLC requires a minimum input of 16.5 V. A transistor was used to raise the output voltage of the onboard Thrill ride enhancement: seat sensors circuitry to trigger the PLC. A 28 V input was placed on the drain and the sensor output that varied from 0 V to 5 V was used at the gate to produce an output Thrill ride enhancement: seat sensors of about 16.67 V. Sedra [1] states that the output voltage of a transistor is determined from:


Vout = Vcc –ic*Rc (3)


A resistance of 3.3k was used at the gate and drain of each transistor to minimize Thrill ride enhancement: seat sensors power and avoid overheating. How the 3.3 k resistor was chosen can be found in the testing and verification section.


^ 2.2 Seat Belt Sensors:

There were several design alternatives for seat belt sensors, including Thrill ride enhancement: seat sensors force sensors and mechanical switches. Hall-effect sensors were selected because they are relatively inexpensive and can easily be mounted on an off-the-shelf seatbelt. The Hall effect sensors Thrill ride enhancement: seat sensors are activated with a minimum of 300 Gauss and carry a rated voltage input of 4.75-24V. The magnets generate a magnetic field that acts perpendicularly to the direction of current and generates Thrill ride enhancement: seat sensors the Hall voltage. Magnet selection and placement played a large role in the seat belt sensor design as described in section 4.2.2. To determine the field strength, the following equation was used.


H = m* (4)


^ 2.3 Programmable Thrill ride enhancement: seat sensors Logic Controller (PLC)

A PLC was used as a state decoder according to Disney’s specification. The PLC takes four inputs from each seat: the capacitance sensor output, seat belt sensor output Thrill ride enhancement: seat sensors, fault and reset signals. It decodes the inputs and produces four outputs for each seat: occupied latched, occupied unlatched, unoccupied unlatched, and fault. The PLC program was written with DirectSoft Thrill ride enhancement: seat sensors32 programming software. It implements the state decoder, fault detection and seat counters with ladder logic. Designing the PLC circuit proceeded with general wiring, programming and compilation, debugging and recoding. The inputs and Thrill ride enhancement: seat sensors outputs were tested independently of the sensors to ensure functionality before the entire system was integrated together.


^ 2.4 Fault Signal

Specifications required a fault signal to determine the status of the capacitance sensor and any PLC Thrill ride enhancement: seat sensors faults. Design alternatives included a mechanical test of the seat sensors, applying a controlled signal to the seat sensors to test functionality, or using the Heartbeat on the QT310 chip Thrill ride enhancement: seat sensors. The seat sensor system used utilizes the Heartbeat signal on the output of the QT310 chip, because this allows for continuous monitoring of the system. The Heartbeat consists of 15us floats superimposed Thrill ride enhancement: seat sensors on the sensor output and indicated a healthy working chip. The floats occur once per burst cycle, or roughly 20ms. The time between burst cycles can be altered by changing the parameter settings on Thrill ride enhancement: seat sensors the QT310. The fault signal is described in sections 3.3 and 3.4. The fault signal will detect PLC faults and problems with the QT310 chip including a PCB power outage and a Thrill ride enhancement: seat sensors fried chip.


^ 2.5 Seat Sensors

Seat sensor design included the construction of the circuit utilizing the QT310 sensor chip, and the construction of a suitable electrode. The basic circuit was taken from the QT Thrill ride enhancement: seat sensors310 data sheet [2]. A resistor was added between the electrode and sampling capacitor (RE1) to ensure that no static charges can be absorbed through the electrode and into the device, thus eliminating electrostatic discharge Thrill ride enhancement: seat sensors. The value of this resistor was chosen to keep the resulting time constant between the resistor and the capacitance from the electrode below 1/6th the transfer time of the chip. The Thrill ride enhancement: seat sensors formula for the time constant is:


t=(RE1)(Cx) (5)


RE1 represents the value chosen for the resistor and Cx represents the capacitance from the electrode. Knowing the chip transfer time of 833ns and the range Thrill ride enhancement: seat sensors of human capacitances between 60-250pF, a range of resistances was available for selection. A midline value for the resistance was chosen to represent a median capacitance at a value Thrill ride enhancement: seat sensors of 560 ohms.


The construction of the electrode alleviated the concern that passengers in adjacent seats might cause a false detection, and also to ensured that a guest could move in the seat without Thrill ride enhancement: seat sensors fooling the sensor . Various sizes and shapes of electrodes were tested to determine the maximum distance to trigger an occupied state. The results can be seen in ^ Table 2.5.


Table 2.5 Electrode Sensitivity

Electrode Description

Max Thrill ride enhancement: seat sensors Distance to Activate Sensor

1” Diameter thin metal circular disc with holes

1.25”

2”x3” Thick metal square with holes

.63”

3.5”x3” Metal mesh screen

2”


An analysis of these results shows that regardless of the electrode chosen, a false trigger from Thrill ride enhancement: seat sensors an adjacent seat is unlikely, so the electrode that has the largest activation distance was chosen. This gave the largest amount of leeway for passenger movement in the seat. Since Thrill ride enhancement: seat sensors the width of an average theme park ride seat is approximately 16-18 inches, it could be advantageous to use an electrode with an even larger range. Having a range of up to Thrill ride enhancement: seat sensors 6 inches in each direction provide for a person centered in any portion of the seat to be detected, and still would not have sensed outside of the intended seat. This modification proved unnecessary because the Thrill ride enhancement: seat sensors system as implemented was very accurate and reliable.


^ 2.6 LED Display

The display was designed solely for the demonstration to give a clear representation of the PLC output states. The display Thrill ride enhancement: seat sensors needed to show all four of the possible states of the device, and make clear the state of the system. LED’s were used because they provide bright, easy to see indicators of output. The Thrill ride enhancement: seat sensors LED’s available were yellow, green, and a red/green multicolor LED. Since four states needed to be shown and easily differentiated, the decision was мейд to mix the red/green multicolor Thrill ride enhancement: seat sensors LED to produce a fourth orange color. For each single-input LED used, a 2.2 kΩ resistor was placed between the output from the PLC and the LED’s input Thrill ride enhancement: seat sensors to lower the voltage from 28 V to 3.8 V according to the following equation.

28 V – (11 mA)(2.2kΩ) = 3.8 V (6)


For dual input LED’s, 4.4 kΩ resistors were placed before each lead to lower the total Thrill ride enhancement: seat sensors input voltage to V as in the following equation.


28 V – (5.5 mA)(5.1kΩ) = 3.8 V (7)


This was done to ensure that the voltage rating of the LED was not exceeded. To mix the Thrill ride enhancement: seat sensors multicolor LED, resistors were put on both the red and green inputs of the LED, and the output voltage from one state was applied to both inputs. This caused the red and Thrill ride enhancement: seat sensors green colors to be activated simultaneously, causing an orange color to be displayed. Each color was then assigned to a state, the LED’s and resistors were mounted onto a PCB board, and Thrill ride enhancement: seat sensors a printout showing which state each LED corresponded to was put onto the board under the LED’s. In actual implementation, more durable LED’s would be chosen, however inexpensive LED Thrill ride enhancement: seat sensors’s proved adequate for demonstration purposes.


^ 3. DESIGN DETAILS


3.1 Capacitance Seat Sensor



Figure 3.1 Capacitance Seat Sensors


Figure 3.1 shows the capacitance seat sensor chip. The QT310 is a digital burst mode charge-transfer sensor. The IC acts as a capacitance Thrill ride enhancement: seat sensors-to-digital converter. Cs is a sampling capacitor and is treated by the chip as a floating store of accumulated charge. Cs undergoes bursts where charge builds, is stored on the capacitor Thrill ride enhancement: seat sensors and read into the device. Cx denotes the capacitance induced from human interaction. Resistors R1 and R2 protect against short-circuiting of the /CAL and /SYNC_I pins. The Thrill ride enhancement: seat sensors calibration switch sends a low signal to /CAL when switched, and allows Cx to be normalized. The transistor amplifies the output voltage from 4.87 V to 16.7 V to be read by the PLC.


Several of the Thrill ride enhancement: seat sensors seventeen chip parameter settings in onboard EEPROM were altered to ensure proper operation. The Max On Duration (MOD) timer was altered from its default value of 10.44s to 177.43s Thrill ride enhancement: seat sensors to give the operator enough time to see the output. The chip recalibrates itself after the MOD period. MOD was then varied and set to infinite. An infinite timeout indicates that the chip never Thrill ride enhancement: seat sensors recalibrates. Although giving an operator the maximum amount of time possible to view the output of the sensor was optimal, setting MOD to infinite posed a problem. It caused the device to Thrill ride enhancement: seat sensors stay on inadvertently even when human capacitance was not present near the electrode. The greatest calibrated value of 177.43s was chosen to optimize viewing time for an operator. The output polarity was also Thrill ride enhancement: seat sensors altered. An Output of high was set using the cloning process. An active high output polarity indicates that the normal inactive polarity of OUT is low. After the QT310’s Thrill ride enhancement: seat sensors parameters were set accordingly, the seat sensors were arranged to give a voltage output of 0V when capacitance was placed in close proximity to the electrode. When capacitance is not placed Thrill ride enhancement: seat sensors near the electrode, the output voltage was 4.8V. All QT310 parameters not listed remain at their default values as listed in the QT310 data sheet [2].


^ 3.2 Magnetic Seat Belt Sensor



Figure 3.2 Magnetic Seat Belt Sensor


Figure 3.2 shows Thrill ride enhancement: seat sensors the Hall-Effect magnetic sensor. When a magnetic field is present, a current and voltage are induced pulling the voltage low. While there is no field, VCC is connected straight to the output Thrill ride enhancement: seat sensors. The pull-up resistor present between VCC and the output protects against short-circuiting.


^ 3.3 PCB Circuit Design




Figure 3.3 shows the complete circuit design that was implemented onto the PCB board. The major Thrill ride enhancement: seat sensors blocks of the circuit are enclosed in dotted lines. The seat sensor and magnetic sensor are outlined in green and orange, and were referred to in 3.1 and 3.2 respectively. The power conversion outlined in Thrill ride enhancement: seat sensors blue converts 28V to 5V for powering the sensors. The fault detection block outlined in red shows the fault detection input to the PLC. The fault signal uses the periodic voltage Thrill ride enhancement: seat sensors drop created by a pull-up resistor connected to the QT310 output as the clock input to a D-latch. The D latch inverts every clock cycle, resulting in a Thrill ride enhancement: seat sensors square wave with a 40ms period. The square wave serves as the fault input to the PLC, which uses it to reset timers in the PLC program as described in section 3.4. If the PLC timer Thrill ride enhancement: seat sensors passes five seconds without reading a transition in the fault input, it triggers a fault output in the system. The four transistors amplify the 5V sensor, fault and reset signals to 16.7V Thrill ride enhancement: seat sensors to trigger the PLC inputs.


^ 3.4 PLC Program

The PLC program was written using DirectSoft32 programming software. The program is written in ladder logic using relays, timers and counters as programming tools. The Thrill ride enhancement: seat sensors PLC takes four inputs for each seat: the seat capacitance sensor, seat belt sensor, fault signal and reset. It generates four outputs for each seat corresponding to each of the four states Thrill ride enhancement: seat sensors as outlined in section 1.4. The program implements the state decoder, fault detection, seat counters, and DV-1000 display interface as described below. A list of component designations, nicknames and descriptions is provided Thrill ride enhancement: seat sensors in Table 3.4. “X” denotes an input, “Y” denotes an output, “C” denotes a control relay, “T” denotes a timer, “CT” denotes a counter, and “V” denotes a location in PLC memory. Background Thrill ride enhancement: seat sensors in PLC coding can be found in the PLC manual and DirectSoft32 programming manual [3], [4].


Table 3.4 DirectSoft32 PLC program component designations, nicknames and descriptions




In figure 3.4a, line one indicates to the DV Thrill ride enhancement: seat sensors-1000 display to load in message mode upon the first PLC program scan. Lines two through seven serve as the seat state decoder, translating combinations of the seat sensor input and belt sensor Thrill ride enhancement: seat sensors input for each seat into the corresponding output. Line eight implements fault detection as described below.




Figure 3.4a PLC program page 1 (Taken from a screen capture in DirectSoft32.)


In figure 3.4b, lines eight and nine Thrill ride enhancement: seat sensors implement fault detection for seat one, while lines ten and eleven implement fault detection for seat two. In line nine, if the seat sensor output is low, the reset input is Thrill ride enhancement: seat sensors not triggered, and the fault input signal is high, timer T1 will begin timing. When the fault signal transitions to low, timer T1 will reset. If timer T1 can reach five Thrill ride enhancement: seat sensors seconds without resetting, then control relay T1 will turn on in line thirteen, causing Seat 1 Fault to turn on. The timer in line eight operates similarly, except it will begin timing Thrill ride enhancement: seat sensors when the fault signal is high. Line twelve turns on the fault control relay C0 if the PLC detects an internal error. Line thirteen turns on the Seat 1 Fault output if T0, T1, or Thrill ride enhancement: seat sensors C0 are high. The fault output from T1 or T0 will turn off when the reset button is pressed. Line fourteen in figure 3.4c operates similarly to line thirteen for Thrill ride enhancement: seat sensors seat two.




Figure 3.4b PLC program page 2. (Taken from a screen capture in DirectSoft32.)


In figure 3.4c, lines fifteen and sixteen turn on control relays C3 and C4 when RESET1 and RESET2 are Thrill ride enhancement: seat sensors turned on, respectively. Line seventeen implements the Seat 1 Counter. While Seat 1 Reset is off, when Seat Sensor 1 input transitions from low to high, Seat 1 Counter will increment. The counter resets to zero when Thrill ride enhancement: seat sensors the Seat 1 Reset is turned on. Line eighteen implements the counter for seat 2. Lines nineteen and twenty load the counter values to the DV-1000 display.




Figure 3.4c PLC program page 3. (Taken Thrill ride enhancement: seat sensors from a screen capture in DirectSoft32.)


The seat sensor system uses the DV-1000 display on the front of the PLC case to display the counts on the seat timers. The DV-1000 was setup Thrill ride enhancement: seat sensors using DirectSoft32. In DirectSoft, clicking on “PLC” on the menu bar, then “Setup”, “DV1000”, and the “Messages” tab will display the following screen. The “Active Text Location” and “Screen editor” sections Thrill ride enhancement: seat sensors were set as in figure 3.4d to display the states of the counters on the DV-1000. Further instructions in DV-1000 setup can be found in the manual [5].




Figure 3.4d DV-1000 setup screen taken Thrill ride enhancement: seat sensors from a screen capture in DirectSoft32.


^ 3.5 PLC and LED display

Figure 3.5 shows the PLC connections to the sensors and the output LED display. All inputs and outputs are routed through terminal Thrill ride enhancement: seat sensors blocks denoted “TB” in the diagram. The PLC consists of several modules, including the CPU, input module and output module. Each module has an independent LED display and display mode switch. The PLC takes eight Thrill ride enhancement: seat sensors inputs, and gives eight corresponding state outputs displayed on eight LED’s.





^ 3.6 Finished Seat Sensor System

Figure 3.6 shows the complete seat sensor system, including the two seats and seat belts constructed, and Thrill ride enhancement: seat sensors the PLC. A PCB was мейд for each seat, and packaged in a plastic container so that the system would be waterproof. The plastic tubs were slid under each seat so they Thrill ride enhancement: seat sensors would not be accessible to the guest. In actual implementation, the PLC and PCB’s would be attached to the underside of the seat bench, inaccessible to the guest.




Figure Thrill ride enhancement: seat sensors 3.6 Photo of finished seat sensor system.


^ 4. DESIGN VERIFICATION


4.1 Seat Sensors

While the design of the seat sensor system is challenging, most of the difficulty arises in the testing portion of the project. The capacitance sensors needed Thrill ride enhancement: seat sensors to be meticulously configured to reliably detect a person, eliminate detection of inanimate objects, and cancel out the effects of water. Sensor functionality was tested and the appropriate chip parameter settings Thrill ride enhancement: seat sensors were determined by connecting the seat sensor chip to the manufacturer’s evaluation board. Functionality of its various parameters was observed. A cloning process was used to program and permit unique combinations Thrill ride enhancement: seat sensors of sensing and processing. The cloning process was performed though the use of the manufacturer’s evaluation board.


4.1.1 Electrode

Electrode sensitivity was tested using various sizes and a variety of electrodes, including Thrill ride enhancement: seat sensors a metal square, wire mesh and coiled metal. The minimum distance required to activate the sensor was recorded. Results were documented and can be found in section 2.5. The electrode was also required to Thrill ride enhancement: seat sensors have a sensitivity range such that a person would not have to be in one specific place to activate the sensor. For this reason, the electrode was chosen such that it produced the Thrill ride enhancement: seat sensors largest range from our test results. A 3 1/2”*3” wire mesh electrode with a high space to conductor ratio produced the best results, as seen in table 2.5. Sensitivity was found to decrease with Thrill ride enhancement: seat sensors a smaller sized electrode. It was desired that a person outside of the designated seat area not activate the electrode. In testing, the electrode range proved to be limited to a few inches Thrill ride enhancement: seat sensors, eliminating that concern.

4.1.2 Sensing

A seat sensor reliability test documenting output due to persons of various weights was performed. Persons weighing 45, 55, and 90 kg tested the sensitivity over a period of fifty trials Thrill ride enhancement: seat sensors each, and the sensor was found to correctly trigger each time. The seat sensor’s imperviousness to inanimate objects was also tested and documented over a period of fifty trials. Objects commonly found in Thrill ride enhancement: seat sensors a theme park were tested. These include a water bottle, Ipod, jacket, backpack, stuffed animal, snow globe, and camera. No false detections were recorded for any object. Sensitivity of the electrode Thrill ride enhancement: seat sensors was important to ensure that the sensor would not trigger when an inanimate object was placed in close proximity of the electrode. Testing various weights was also necessary to ensure that Thrill ride enhancement: seat sensors the sensor was not dependant on weight and was only triggered when capacitance was present.


^ 4.2 Seat Belt Sensors


4.2.1 Reliability

Seat belt sensor reliability was tested and documented over a period of fifty trials per Thrill ride enhancement: seat sensors seat belt by latching the belt repeatedly. The seat belt sensors were tested to ensure that they were accurately set up. When triggered, the seat belt sensor outputted 4.87 V and triggered correctly Thrill ride enhancement: seat sensors every time.


^ 4.2.2 Magnet Placement

Magnet placement was important to ensure proper function of the seat belt sensor. Four different types of magnets were purchased, which varied by width, length and thickness Thrill ride enhancement: seat sensors. Field strength of 300 Gauss was required to activate the sensor. Field strength per distance from the magnet was considered to allow for the maximum strength of necessary to trigger the seat belt sensor. Figure 4.2.2 indicates Thrill ride enhancement: seat sensors the total field strength of magnet per distance away from seat belt sensor. The seat belt sensors yielded a total field strength of 430 Gauss when a magnet of 0.25”*0.25”*0.25” was placed at a Thrill ride enhancement: seat sensors distance of about 0.25” away from the seat belt sensor. This configuration yielded field strength greater than the sensor threshold of 300 Gauss and was used in the final design.




Figure 4.2.2 Total Field Strength Thrill ride enhancement: seat sensors of Nd-Fe-B Magnet


^ 4.3 PLC Control Signals

Giving test inputs to the system and comparing outputs tested the PLC output signals as described in section 1.4. After some debugging, the PLC was Thrill ride enhancement: seat sensors found to output states correctly. Table 4.3 indicates the inputs and outputs that correspond to the LED’s on the front of the PLC that were used in debugging. These are separate Thrill ride enhancement: seat sensors from the LED output display used for the demonstration.


Table 4.3 Corresponding PLC LED’s

INPUTS

PLC LED




OUTPUTS

PLC LED

0

Seat Sensor 1




0

Seat 1 Occupied, Latched

1

Seat Sensor 2




1

Seat 1 Occupied, Unlatched

2

Belt Sensor 1




2

Seat 1 Unoccupied, Unlatched

3

Belt Sensor 2




3

Seat 1 Fault

4

Seat 1 Fault




4

Seat 2 Occupied, Latched

5

Seat Thrill ride enhancement: seat sensors 2 Fault




5

Seat 2 Occupied, Unlatched

6

Seat 1 Reset




6

Seat 2 Unoccupied, Unlatched

7

Seat 2 Reset




7

Seat 2 Fault


^ 4.4 Power Conversions

Power conversions were tested independently to ensure proper voltage supplied to each component. After initial simulation in Pspice, the power conversions Thrill ride enhancement: seat sensors from 28 V to 5 V and 5 V to 28 V were tested by connecting the power conversion portion of the circuit only and observing its voltage and current with a voltmeter. Results were documented, can be found Thrill ride enhancement: seat sensors in Table 4.4, and proved successful. The actual voltage that triggered the sensors was 4.87 V. The actual voltage that triggered the PLC was 16.67 V.


Table 4.4 Voltage Conversion

Voltage Regulator

Vin (V)

Vout Thrill ride enhancement: seat sensors (V)

Iout (mA)

28

4.87

10










Transistor

Vin (V)

Vout (V)

Iout (mA)

4.87

16.67

8.0



The transistor resistances were altered and tested by increasing the resistance value with common resistances found in the lab to eliminate overheating. The power per resistance Thrill ride enhancement: seat sensors can be found in Figure 4.4. At 3.3k, the resistors no longer overheated, with 0.24W flowing through each. This eliminates the overheating problem, and 3.3k resistors were used in the finished system.


^ Figure Thrill ride enhancement: seat sensors 4.4: Power per Resistance

4.5 Water Tolerance

The presence of water on the seat greatly affects the ability to detect the presence of a person sitting down, since water alters the dielectric Thrill ride enhancement: seat sensors constant of the environment near the sensor similarly to that of a human. The seat was covered with Saran wrap so that it would not be damaged, and the system still accurately detected the presence Thrill ride enhancement: seat sensors of a person with the plastic coating. Introducing 100 ml of water absorbed by several cotton balls tested system water tolerance. The cotton was placed directly on the seat. The amount of water Thrill ride enhancement: seat sensors and cotton balls was gradually increased from 0ml to 1000 ml in 100 ml increments, as specified in the design review. The wet cotton never triggered the seat sensor. The test was Thrill ride enhancement: seat sensors continued by adding water in 100 ml increments until 3 liters of water covered the seat, and still no false detections were recorded. The wet cotton was then placed in a plastic tub Thrill ride enhancement: seat sensors on the seat and water was added up to 5 L. No false detections were recorded, and the system passed the water tolerance test.


^ 4.6 Testing Conclusions

In conclusion, the seat sensor system passed all tests specified Thrill ride enhancement: seat sensors in the design review. The seat sensor passed reliability tests including repeated sensing, sensing persons of different weights, and filtering out inanimate objects. The magnetic sensors proved to be reliable over fifty trials Thrill ride enhancement: seat sensors, and magnet placement testing was completed. PLC control signals and power conversions were tested independently for functionality and passed all tests. The system passed the water tolerance test with up to Thrill ride enhancement: seat sensors 5 L of water on the seat with no false detections.


5. COST


5.1 Parts

Table 5.1 Parts List




5.2 Labor
Each person worked a total of 10 hours a week for 12 weeks.  Each person charged a total of Thrill ride enhancement: seat sensors $40 per hour.

Total Cost of Labor=$40/hour * 2.5 * 12 weeks * 10 hours/week * 3 engineers = $36,000

5.3 Total Cost
Summing the cost of all parts plus the total cost of labor as found in sections 5.1 and 5.2 respectively, the total cost is Thrill ride enhancement: seat sensors $39,238.40.


6. CONCLUSIONS


In conclusion, the seat sensor system design was successfully build. It met all specifications and passed all tests specified in the design review. While the system passed all tests, further testing is recommended Thrill ride enhancement: seat sensors to fully verify reliability before implementing the system in a theme park. While testing was thorough for the time allotted in the semester, fully ensuring 99.99% reliability requires many more trials Thrill ride enhancement: seat sensors of all tests performed. Further testing in seat sensor reliability and water tolerance is recommended to ensure the system will function under the demanding requirements in a ride setting. While the Thrill ride enhancement: seat sensors seat sensor system performed very well in the senior design classroom, modifications must be мейд to integrate the system with Disney’s current proprietary seat belt system. The design will be given to Disney’s Thrill ride enhancement: seat sensors engineers for review and possible implementation. The seat sensor system has great potential for expansion. In the future, it could be modified to detect guests while the ride is in motion, and Thrill ride enhancement: seat sensors to verify seat occupancy upon restart of the ride. Both of these modifications would help ensure guest safety.


REFERENCES


[1] Adel S. Sedra and Kenneth C. Smith, Microelectronic Circuits. New York: Oxford Thrill ride enhancement: seat sensors University Press, 2004.

[2] Quantum Research Group Technical Staff, Qprox QT310 Capacitance Sensor IC, Quantum Research Group, 2002, http://www.qprox.com/downloads/datasheets/qt310_103.pdf

[3] Automationdirect.com Technical Staff, D2-USER-M, Automationdirect.com Incorporated, 2003, http Thrill ride enhancement: seat sensors://web3.automationdirect.com/static/manuals/d2user/d2uservol1.pdf.

[4] Automationdirect.com Technical Staff, DirectSoft32 Programming Software Users Manual, Automationdirect.com Incorporated, 1999.

[5] PLCDirect Technical Staff, D-24VIEW-M, PLCDirect Incorporated Thrill ride enhancement: seat sensors, 1998.





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