p13571 d3 video analytics: me detailed design...

P13571 D3 VIDEO ANALYTICS: ME Detailed Design Review

ME -1 | D 3 V I D E O A N A L Y T I C S

Table of Contents: 1. Project Overview ME-2

a. Project’s Design Intent ME-2

b. Objectives ME-2

c. The Design So Far ME-2

d. Deliverables ME-2

e. Key Issues and Risks ME-2

2. Customer Needs / Specifications ME-3

3. Updated Risk Assessment ME-4

4. Bill of Materials ME-5-6

5. The Design ME-7-9

a. M12 Lens Configuration ME-7

b. Seals & Gaskets ME-8-9

6. FEA Analysis ME-10-14

a. Thermal Management Analysis ME-10-14

7. Preliminary Test Plans ME-15-26

a. Drop Test ME-15-17

b. Heat Dissipation Test ME-18-19

c. Dust Tight Test ME-20-21

d. Water Spray Test ME-21-24

8. Appendix ME-25-30

a. Schematics ME-25-29

b. References ME-30

c. Manufacturers & Distributors ME-30



Project Overview

Project’s Design Intent The project’s design intent, from a mechanical a perspective, is to

enclose sensitive electric, optical, and mechanical components in a

ruggedized enclosure and maintain ease of assembly. Ruggedized

is defined as water proofed and dust proof, in accordance with the

IP64 standard.

Objectives 1. Design an enclosure within the size constrains of the

customer’s specifications.

2. Design must allow for an operational environment within

the enclosure for all electrical and mechanical components.

3. Design must meet IP64 standards.

4. Enclosure components must be able to withstand high and

low automotive temperatures.

The Design So Far Through multiple discussions with our advisors, both at D3 and RIT,

the design has converged onto a single design, which, as shown by

FEA Analysis, promises to meet the customer’s needs and

specifications.

Deliverables A design with the ability to dissipate the heat generated by

the electrical components.

A design that can withstand impact of a 2 foot drop onto

carpeted flooring.

Ease of assembly.

Key Issues and Risks Insufficient time to meet all customer needs.

Current design fails to meet customer specifications.

Heat dissipated by design is insufficient for high

temperatures.

Unable to withstand impact from 2 foot drop on any

surface.

Design has a high tolerance stack up.

Optical components do not align correctly.

BNC connector is not secured properly.



Customer Needs / SpecificationsCN# Importance Description Comments/

Status

Enclosure

CN1 3 The enclosure shall be one inch cubed. Length of unit is negotiable

CN2 3 The enclosure shall be ruggedized.

CN3 2 The enclosure shall be waterproof excluding lens mount and connector.

CN18 3 The enclosure shall support C-mount lens.

CN19 2 The enclosure shall have a mounting system.

CN20 1 The enclosure should be aesthetically pleasing.

Lens

CN8 3 The device shall support an M12 lens.

CN9 3 The device shall support a New Scale M3F Focus Module.

Figure 1: Customer Needs.

S # Importance Source Specification (Metric)

Unit of Measure

Marginal Value

Ideal Value

Comments/ Status

Enclosure

S1 3 CN1 The enclosure shall be a 1.2" x 1.2" x N package. Length of N is negotiable.

Inches 1 in3

S2 3 CN2 The enclosure shall be water resistant. Connector and lens excluded.

IP64 IP67

S3 2 CN2 The enclosure shall be impact resistant.

Drop Height

2ft Beyond Range

S4 2 CN17 The enclosure shall be oil resistant.

UL Oil Res II

S5 3 The enclosure shall withstand temperatures relevant to the electronics.

°C -40 to 85 Max. Temp. inside 125°C.

S16 2 CM13 Camera needs to have front, back, and side-mount capabilities.

Yes/No

Lens

S17 CN8 The system shall support an M12 lens.

Yes/No

S18 3 CN18 The system shall support a C-mount lens.

Yes/No

S7 3 CN9 The system shall support an M3F focus module.

Yes/No

Figure 2: Customer Specifications.



Updated Risk Assessment ID Risk Item Effects Cause L S I Actions to

Minimize Risk Owner

1 Tolerance Stack Up

Optical Components

are misaligned

Incorrect calculations and

machining of parts

1 3 3 Multiple checks on calculations and drawing specs.

Cameron and Jose

2 IP64 Limited ingress of dust and

water

Push for smaller O-rings

1 3 3 Search for extra room for

components

Jose

3 Shifting Connector

Tension on PCBs and on

Optics

Connector not held in place properly

2 2 4 Remove connector from PCBs in the

future

Cameron

4 Heat Dissipation

Unable to effectively

dissipate heat in a high

temperature environment

Design and material limitations;

Compromises made for electrical and

optical components

1 3 3 Heat dissipation simulations; Heat

sinks

Cameron

5 Impact Enclosure does not meet

rugged requirement

Design and material limitations

2 3 6 Drop test simulations

Jose

6 Drop Test Simulation

Unable to claim design as

ruggedized

Simulation software and hardware

limitation; limited understanding of

software

3 3 9 Alternative software or

techniques to simulate drop test

Jose

7 Bill of Materials

Delay on ordering of

parts

Limited information on parts and prices

1 2 2 Direct contact with manufactures and

distributers

Cameron and Jose

Figure 3: Up-to-date Risk Assessment



Bill of Materials

# Supplier Material Part Number

Qty. Price Per Unit

Total Part

Products to be Purchased

1 McMaster Al 6061 Alloy, 1.5" X 1.5" X 12"

9008K61 1 $20.07 $20.07 Lens Cover


9008K61 0 $20.07 $0.00 C-Mount Cover


9008K61 0 $20.07 $0.00 Sensor Mount


9008K61 0 $20.07 $0.00 M12 Sensor Mount


9008K61 0 $20.07 $0.00 Housing Rear

6 McMaster Metric Dowel Pins, M1.5 Dia X 8

93600A056 2 $9.20 (Pkg. of

50)

Dowel



7 McMaster Metric Pan Head Machine Screws, M2 X 0.4 X 8 (M2--#1 Drive)

90116A015 1 $7.67 (Pkg. of

100)

M2 X 0.4 X 8 Pan Head

8 McMaster Metric Pan Head Machine Screws, M2 X 0.4 X 16 (M2--#1 Drive)

90116A025 2 $10.95 (Pkg. of

100)

M2 X 0.4 X 16 Pan Head

9 McMaster Metric Flat Head Philips Machine Screws, M2 X 0.4 X 20 (M2--#0 Drive)

92010A010 4 $7.71 (Pkg. of

100)

M2 X 0.4 X 20 Flat Head

10 McMaster Ultra-Conductive Copper (Alloy 101) 6” X

6” X 0.032”

89675K11 1 $12.85 $12.85 Cold Fingers

11 McMaster Aluminum Tubing, 0.014” OD X 0.097” ID

X 1’

7237K14 1 $2.12 (Pkg. of

3)

PCB Spacers

12 Grainger Helicoil Insert, 304SS, M2 X 0.4

4DAG5 7 $87.80 (Pkg. of

100)

Helicoil Inserts

13 Gallagher Seals

Parker O-Ring, 28.30mm ID X 1.78mm

W

2-024-LM159-70

1 $0.79 (Pkg. of

100)

O-Ring Housing Gasket

14 Gallagher Seals

Parker O-Ring, 25.07mm ID X 0.79mm

W

5-139-LM159-70

2 $2.11 (Pkg. of

100)

Lens Gasket

15 Gallagher Seals

Parker O-Ring, 4.47mm ID X 1.78MM W

2-008-LM159-70

1 $0.75 (Pkg. of

100)

Connector Gasket

16 Thorlabs Mounted 400 nm LP Filter, SM1

FGL280M 1 $46.80 $46.80 Lens Filter

17 Parker THERMATTACH Double-Sided Themal

Tape

T418 1 Thermal Tape

18 Parker CHO-THERM Insulator Pad

T500 1 Thermal Pad

# Supplier Material Part Number

Qty. Price Per Unit

Total Part

Products Possibly Provided by D3

19 Digi-Key Newscale M3-F Focus Module

DK-M3F-1.8-TRK-1.5-S-ND

1 $702.00 $702.00 M3-F Focus Module

20 Sunex M12 Lens 1 $49.00 $49.00 M12 Lens

Total 27 $959.52



The Design

M12 Lens Configuration

Exploded View

Section View



Seals & Gaskets

Front/Rear Seal

The groove and o-ring are designed to provide a lock-tight seal for an external pressure of ranging from

0-690kPa, which is higher than IP64 requirements. The design of the groove is based of a research

paper, Stresses and Deformation of Compressed Elastomic O-ring Seals by Itzhak Green and Capel

English, which describes equations for solving groove width and depth based on the peak contact stress

and the elastic modulus of the o-ring. Due to size constrains, the groove width was kept equivalent to

the o-ring wire diameter. The equations used are as follows:

Loading Case c d e

Restrained Axial Primary Wall 3.8295 -23.0013 82.6963

Restrained Axial Lateral Wall 2.6584 -16.1793 71.5999

( )

( )

( )

13

13



( ( ) )

Nomenclature

d O-ring Diameter

E O-ring Elastic Modulus

Smax Peak Contact Stress

δ Normalized Squeeze

δij Equivalent Normalized Squeeze

x Displacement

h Groove Depth

l Groove Width

Filter Seal

Connector Seal

14

14

15



FEA Analysis

Thermal Management Analysis

As the customer the needs document depicts, the assembly must withstand

temperatures ranging from -40 deg C to 105 deg C. During the designing phase, the

temperature of 125 deg C was used as the high end thermal limit. In an effort to dissipate the

heat generated to the outside, several factors were taken into account.

Conduction (PCB to Outside Surface):

Thermal Pads (k=5 W/m^2*K)

Cold Finger

Assembly

Material Selection

Al 6061 (k=240 W/m^2*K)

Copper (k=360 W/m^2*K)

Convection

Maximizing Surface Area

Heat Sink

Convection Coefficient Analysis

Estimated k values W/m*K

The cold finger was implemented to decrease the thermal

resistance from the FPGA to the housing by creating a low

resistance pathway for heat flow. Several different cold finger

geometries were tested. After several trails, three large factors

influencing the FPGA temperature are the cold finger material,

cross section shape, and pathway distance. Copper was material of

choice having a high conductance coeffient of about 360 W/m K

compared to 50 W/m K for sheet metal. The geometry also has a

large impact, the idea of cold fingers is to transfer energy the

fastest and possible and since heat flux depends on the thermal

resistance, the larger the scross sectional area of the sheet, the

more can pass.

The basic equation of conductance:

Resistance’[R’] =Distance[L]/Coefficient of Conductivity [K]*Area [A]

Acrylic 0.2

Aluminum 240

Apple (85.6% moisture) 0.39

Brick dense 0.17

Brickwork, common 0.02

Copper 360

Carbon Steel 54

Epoxy 0.35

Glass 1.05

Gold 310

Iron 80

Iron, wrought 59

Iron, cast 55

Magnesium 156

Polypropylene 0.1 - 0.22

Polystyrene, expanded 0.03

PTFE 0.25

PVC 0.19

Pyrex glass 1.005

Steel, Carbon 1% 43

Stainless Steel 14

Wood 0.12



Figure 1: Comparison of Cold Finger Materials, Models from 2/1/1

F

Figure2: Cold Finger Geometry Figure3: Iso-Contours, 1 Watt at FPGA

By implementing a three prong design, cross sectional area is tripled, reducing the thermal

resistance of the cold finger by a factor of three.



Thermal pads are useful by providing the interface between thermal components,

however, their thermal conductivity is still not great. This impacts our conductive resistivity. To

reduce the resistance the smallest possible thickeness should be chosen with exception with

thermal pads which rely on compression.

Table 1: Comparing Thermal Interfaces

Optimization

Heat Sink

On the rear of the housing the heat sink fins are spaced to 5mm. This spacing

optimizes the balance between the number of fin and the interference of thermal boundary

layers.

Presence of a Stand

In high temperature applications (105 deg C) it is unlikely that the method of

attachment will be a plastic due the low service temperatures. The options to choose from then

are metals or ceramics. Metals have a high thermal coefficient that provide an excellent source

of sinking heat, Ceramic don’t.

Interface Coef. Of Conduction

Thickness (mm)

Temp (deg C)

Tape .5 .25 -30/125

Gap Filling Foam 1 .25 - 5 -55/200

Hi-Performance Gap Filling Foam

5 .25 - 5 -55/200

Gel .7 .1-.25 -55/200

Grease .9 -55/200

Potting 3 -55/150



Figure 4: Camera Housing on Stainless Steel Plate with Bosses 1.8 Watts generated

Figure 5: Camera Housing Resting on Ceramic Plate with 1 Watt of generation



Thermal Results

Maximum Wattage Produced while maintaining 125 deg C at 105 deg C ambient:

Convection only

M12 and M3F Assembly: .98W

C-Mount: .89 W

Conduction and Convection:

Stainless Steel (k=14 W/mK)

M12 and M3F Assembly: 2.5W

C-Mount: 2.1 W

Ceramic (k=.25 W/mK)

M12 and M3F Assembly: 1.4W

C-Mount: 1.2 W



Preliminary Test Plan

Drop Test This test is designed to test the durability of the enclosure against impact. The test shall consist of a

simulated drop onto carpeted flooring using a Precision Drop Tester from various heights (maximum of

2ft). All tests will have an initial velocity of 0m/s. Drop impact conditions will include: surface-to-

surface, edge-to-surface, and vertex-to-surface.

Start Date: Finish Date:

Engineer conducting test:

Assistant:

Conditions:

Ambient Temperature:

Other:

Equipment:

Precision Drop Tester

Observations:

Visual defects before test?: □Yes □No

If yes, explain:

Tests:

1. Surface-to-Surface Test

a. Drop Height:

i. Results: □Major Defects □Minor Defects

ii. Comments:

b. Drop Height:


ii. Comments:



c. Drop Height:


ii. Comments:

d. Drop Height:


ii. Comments:

2. Edge-to-Surface Test

a. Drop Height:


ii. Comments:

b. Drop Height:


ii. Comments:

c. Drop Height:


ii. Comments:

d. Drop Height:


ii. Comments:

3. Vertex-to-Surface Test

a. Drop Height:


ii. Comments:

b. Drop Height:


ii. Comments:



c. Drop Height:


ii. Comments:

d. Drop Height:


ii. Comments:



Heat Dissipation Test This test consists of mounting a PCB with a single resistor, which is capable of dissipating a certain

amount of heat, into the enclosure to tests the enclosure’s capabilities to dissipate heat under certain

conditions. The resistor will produce 1 to 2 Watts of heat to simulate the heat produced by the major

electrical components, which the enclosure must dissipate. The conditions under which the test will be

conducted are: high temperatures (105°C), low temperatures (-40°C), and room temperature (20°C). An

Omega Thermocouple Data Logger, or similar, will be used to record the temperatures inside the

enclosure and on its outside surface.



Assistant:

Equipment:

Omega Thermocouple Data Logger

If other, please specify:

Tests:

1. High Temperature Test

a. Resistor (W):

i. Ambient Temperature:

ii. Temperature Inside Enclosure:

iii. Temperature On Surface of Enclosure:

iv. Comments:

b. Resistor (W):




iv. Comments:

2. Low Temperature Test

a. Resistor (W):




iv. Comments:



b. Resistor (W):




iv. Comments:

3. Room Temperature Test

a. Resistor (W):




iv. Comments:

b. Resistor (W):




iv. Comments:



Dust Tight Test This is a test on the enclosure’s and seal’s capability to completely protect the enclosed components

from the ingress of dust; in other words, it’s ability to meet the Ingress Protection Rating 64 (IP64) for

solid materials. The test will be conducted by submerging the sealed enclosure in shallow pool of water.

The shallow pool of water is defined as having a depth 10mm greater than the height of the enclosure

(40.5mm total depth). All components will be removed from within the enclosure before the beginning

of the test and the BNC connector mounting hole will be sealed. At the beginning of the test, the

enclosure should be placed securely at the bottom of the water tub. When submerged, the enclosure

should prevent the formation of air bubbles near the seals for at least 30 minutes; the formation of air

bubble around the seals before 30 minutes will be taken as proof that the seals are ineffective at

protecting the components from dust.



Assistant:

Conditions:


Humidity:

Other:

Observations:


If yes, explain:

Equipment:

Large Water Tub


Test:

1. Submerge Test

a. Water Depth:

b. Water Temperature:

c. Start time of test:

i. Formation of bubbles at Front/Rear Seal? □Yes □No

If yes, specify time and comment:



ii. Formation of bubbles at Filter Seal? □Yes □No


iii. Formation of bubbles at Connector Seal? □Yes □No




Water Spray Test This test calls for the enclosure to be subjected to a water spray from all directions. The components

within the enclosure must be completely protected from the ingress of water for this test to be

successful, which is a higher requirement than the Ingress Protection Rating 64 (IP64); IP64 permits a

limited ingress of water, which is unfavorable for our device. In accordance with IP64, the enclosure will

be subjected to a volume of water of 10 LPM at a pressure of 100 kPa from all directions for 5 minutes

each. Additionally, the water nozzle used in the test will be held in place at a distance of 3m. At the end

of the test, the enclosure will be inspected and then dried before the start of the next test. If any water

or evidence of moisture is found within the enclosure during inspection, that test has failed and the

overall test has failed.



Assistant:

Conditions:


Humidity:

Other:

Observations:


If yes, explain:

Equipment:

Water Nozzle


Test:

1. Front Surface Test

a. Any parts replace before test? □Yes □No

If yes, which and why:

b. Flow Rate:

c. Pressure:

d. Start Time: End Time:



e. Water/Moisture in enclosure? □Yes □No

If yes, describe:

2. Back Surface Test



b. Flow Rate:

c. Pressure:



If yes, describe:

3. Right Surface Test



b. Flow Rate:

c. Pressure:



If yes, describe:

4. Left Surface Test



b. Flow Rate:

c. Pressure:



If yes, describe:

5. Top Surface Test



b. Flow Rate:



c. Pressure:



If yes, describe:

6. Bottom Surface Test



b. Flow Rate:

c. Pressure:



If yes, describe:



Appendix

Schematics

C-Mount Cover



Lens Cover (M12 and M3-F)



Housing Rear Cover



M12 Sensor Mount



Sensor Mount



References STRESS AND DEFORMATION OF COMPRESSED ELATOMERIC O-

RING SEALS. Green, Itzhak and English, Capel. 14th

International Conference on Fluid Sealing, Firenze, Italy, 6-

8 April 1994. Organized by BHRGroup Limited, Cranfield,

Bedford, MK43 0AJ, UK.

Manufacturers & Distributors Digi-Key Corp. www.digikey.com

Gallagher Fluid Seals, Inc. www.gallagherseals.com

Grainger www.grainger.com

McMaster-Carr www.mcmaster.com

Parker Hannifin Corp. www.parker.com

Thorlabs www.thorlabs.us

Sunex Inc. www.optics-online.com

http://www.digikey.com/

http://www.gallagherseals.com/

http://www.grainger.com/

http://www.mcmaster.com/

http://www.parker.com/

http://www.thorlabs.us/

http://www.optics-online.com/

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