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Detailed Design

Table of Contents 1 Prototyping, Engineering Analysis, Simulation 1.1 Material Simulations 1.2 Heat Simulations 1.3 Vibration Analysis 2 Drawings, Schematics, Flow Charts, Simulations 2.1 Case Drawings 2.2 Circuit Schematic 3 Software Processes 4 Bill of Material (BOM) 4.1 Development BOM 4.2 Total Cost 5 Navigation Links

Prototyping, Engineering Analysis, Simulation

Material Simulations

Several Simulations were ran on ANSYS to help see how several different types of materials react to the harsh environment of the inside of a compressor. The four materials chosen to take a clsoer look at are: Acetal (Delrin-150), Polysulfone, Polyester, and Aluminum (6061). The properties used in the simulations were:

Property	Acetal (Delrin-150)	Polysulfone	Polyester	Aluminum 6061
Max Operating Temp	180F	285F	210F	500F
Yield Strength	10400psi	10900psi	12400psi	40000psi
Modulus	450ksi	390ksi	490ksi	1000ksi
CTE	278uin/in*F	29.4uin/in*F	33uin/in*F	13.1uin/in*F
Cost: 1.5"x6"x6" Sheet	$35.71	$147.83	$48.57	$53.44
Max Deformation	0.060"	0.006"	0.007"	0.003"
Max Stress	N/A	6862psi	9744psi	N/A

The conditions tested were a 100psi pressure applied to the external faces of the case, along with a 200°F temperature applied to the entire case.

The results are as followed:

Simulation of Acetal (Delrin-150)	Simulation of Polysulfone (PSU)
Simulation of Polyester (PET-P)	Simulation of Aluminum-6061

Red shows the areas of highest displacement, while blue shows the least. The aluminum case provided the least deformation, and also is the cheapest, strongest and most readily available. Concerns of electrical and thermal conductivity arise, but will be dealt with.

Heat Simulations

A heat model was developed in ANSYS as well as Excel to see the effects that various ambient temperatures have on the internal components of the DAQ. The limiting component is the lithium polymer battery chosen for the power source, which has a max operating temperature of 60C. The PRP stated that the DAQ could see temperatures of up to around 95C. Various simulations were run to see how long the device could last in this kind of condition. The 3D model created for ANSYS Simulations looks like:

The results of ANSYS simulations are as follows:

ANSYS model with ambient temperature at 55C

ANSYS model with ambient temperature at 95C

The battery was probed, which allowed ANSYS to provide numerical values per step for the battery. These values were graphed vs time: The times for when the battery reaches its maximum are 825 seconds for the 55C ambient temperature, and 705 seconds for the 95C.

These results are pretty unbelievable. This is probably due to the fact that this ANSYS model does not have a large temperature reservoir that provides an equilibrium when the ambient temperature is reached (or slightly exceeded). So further analysis is required.

An Excel File was created from scratch using the methods of heat transfer. The heat model used was broken down into different systems of varying detail:

Fig. 1: Heat System Model

Fig. 2: Heat System Model, Closer Look

Fig. 3: Thermal Resistance Model

Figure 1 shows the top-most and most general system. It showcases where the heat is being generated, where it is going, and the surrounding environment by using familiar objects that would actually be used.

Figure 2 takes a step closer, narrowing in on the specific components that will be used in this heat model.

Finally, Figure 3 shows the bare-bones resistive model that will be used for actual calculations. It is a very simple worst-case scenario that will provide a general idea of heat generation.

After the heat model was created, several simulations were run using different inputs (mainly ambient temperature, insulation thickness, etc). The first simulation had no external insulation surrounding the box. This scenario was run twice, once at an ambient temperature of 95C and once at 25C. The results are found in Figure 4. At Tamb = 95C, the battery will only last 28 seconds before it reaches its max operating temperature (much more believable than the ANSYS model). However, with an ambient temperature of 25C (normal, room temperature), there is no point in which the battery reaches its maximum operating temperature, which makes physical sense. So the next logical step is to add insulation and compare results. The insulation added was a standard plastic insulating material (k value of 0.03 W/m*K) with a thickness of 1 cm. Too much thicker and the device will become bulky. The results, in Figure 5, show that even with the insulation, the battery can only last 154 seconds. This is problematic, as that's not nearly a long enough operating time.

Fig. 4: Excel Model - w/o Insulation

Fig. 5: Excel Model - w/ Insulation

From this data, we have been left with several options. In order to reduce the heat problems we can either pursue different power techniques (other than LiPo), or we could pursue some sort of active cooling techniques. Neither of those options were appealing to the customer. So the customer decided it would be best if the specification was reduced from a maximum operating temperature of 95C to the battery's limit of around 65C.

Vibration Analysis

An FFT (Fast Fourier Function) Vibration Analysis was performed on legacy acceleration data from the compressor to ensure that the device will stand up to any environmental vibrations. The results are below:

X-axis	X-axis (Zoomed in)
Y-axis	Y-axis (Zoomed in)
Z-axis	Z-axis (Zoomed in)

The X-axis and Z-axis both peaked at approximately 6 Hz, and the Y-axis peaked at 12 Hz. These numbers are exactly what we expected based on previous data.

Drawings, Schematics, Flow Charts, Simulations

Case Drawings

The cases selected for the devices are from Hammond Manufacturing.

The aluminum case (Series: 1590Z) is meant to house the device being used in harsh conditions. It's thicker, watertight, and has included standoffs. It comes in various sizes, and for reference the data sheet: 1590Z

The plastic case (Series: 1551 FL) is smaller and lighter, perfect for the standard laboratory conditions device. Again, it comes in various sizes, and for reference the data sheet: 1551 FL

Circuit Schematic

The circuit schematic below, shows the first version of the schematic that will be used to make the PCB layout. This shows all of the connections for all of the components that are needed in the circuit.

Software Processes

Bill of Material (BOM)

Development BOM

Item	Source for Price	Price	Quantity	Total Price	Vendor	Actual Cost	Order Date	Receive Data
FRDM-KL05Z Development Board	Mouser	$12.95	2	$25.90	Mouser	$25.90	02/27/14	03/10/14
SWD Connector		TBD	2	TBD			---	---
SWD Cable		TBD	1	TBD			---	---
MicroSD Breakout Board	SparkFun	$9.95	1	$9.95	SparkFun	$9.95	03/05/14	03/11/14
LiPo Charger Dev Board	SparkFun	$19.95	1	$19.95	SparkFun	$19.95	01/21/14	01/29/14
JST Battery Connectors	Sparkfun	$0.95	4	$3.80			---	---
			Total Price	$59.60	Total Actual Cost

Total Cost

Order	Subtotal	Shipping	Total Price	Order Date	Receive Data
SparkFun Order 01/21/2014	$19.95	$3.69	$23.64	01/21/14	01/29/14
Mouser Order 02/27/2014	$131.00	$6.99	$137.99	02/27/14	03/10/14
Advanced Circuits Order 02/27/2014	$33.00	$19.64	$52.64	02/27/14	03/11/14
SparkFun Order 03/05/2014	$60.50	$7.75	$68.25	03/05/14	03/10/14
Advanced Circuits Order 04/03/2014	$33.00	$38.73	$71.73	04/03/14	04/10/14
Mouser Order 04/09/2014	$40.28	$6.99	$47.27	04/09/14	--
Box Order	$23.95	--	$23.95	--	--
Total BOM Predicted	$450.12	N/A	$450.12	--	--
Totals BOM Spent	$334.39	$91.08	$425.47	--	--

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