Table of Contents
Prototyping, Engineering Analysis, Simulation
Material SimulationsSeveral 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|
|Cost: 1.5"x6"x6" Sheet||$35.71||$147.83||$48.57||$53.44|
The results are as followed:
Heat SimulationsA 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:
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:
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.
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.
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:
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 DrawingsThe 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 SchematicThe 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.
Bill of Material (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|
|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|
|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||--|
|Total BOM Predicted||$450.12||N/A||$450.12||--||--|
|Totals BOM Spent||$334.39||$91.08||$425.47||--||--|
|MSD I||MSD II||Overview|