ENG102 – Engineering Design 1 Design Project 2
Detailed information on design challenges
Note that each group member should individually attempt a separate one of the Matlab function based challenges below (and reflect this in your ePortfolio). You should work as a team to complete the other design challenges.
Matlab based design challenges
For each design challenge below you should write a Matlab function to perform the calculations. The outputs of some of these functions will be inputs to other functions so please ensure you are writing your functions generally to allow for this. Refer to attached circuit diagram.
- Calculate NTC resistance value
Design a Matlab function which can evaluate the NTC resistance based on the datasheet parameters (see Murata NTC Thermistor datasheet). To select 𝑅𝑅1 and 𝑅𝑅2 the result of 𝑅𝑅1||𝑅𝑅2 should be equal to the NTC resistance calculated for the temperature limit condition.
- Calculate resistor values for the shunt regulator.
Design a Matlab function which can evaluate the resistor value (𝑅𝑅7||𝑅𝑅9) of the shunt𝑅𝑅8
𝑅𝑅8 + 𝑅𝑅7||𝑅𝑅9
regulator based on the following equation. = 2.5
𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑚𝑚𝑣𝑣𝑣𝑣 𝑣𝑣𝑜𝑜 𝑏𝑏𝑚𝑚𝑣𝑣𝑣𝑣𝑣𝑣𝑏𝑏𝑏𝑏
Design a Matlab function which can evaluate the resistor value (𝑅𝑅12||𝑅𝑅13) of the low voltage cut out based on the following equation. You will need to use the lowest useable voltage for the energy storage device in your calculation.
3. Calculate resistor values for the low voltage cut out.
𝑅𝑅12||𝑅𝑅13 1.24 = 𝑚𝑚𝑚𝑚𝑜𝑜𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑚𝑚𝑣𝑣𝑣𝑣 × 𝑅𝑅10 + 𝑅𝑅12||𝑅𝑅13
Design a Matlab function to determine the resistors (𝑅𝑅2||𝑅𝑅3) for the LED constant current drive based on the equation given below.
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4. Calculate the resistor values for the LED constant current drive.
𝑄𝑄2(𝑣𝑣𝑏𝑏𝑣𝑣) 𝐼𝐼 = 𝑅𝑅2||𝑅𝑅3
Where 𝑄𝑄2(𝑣𝑣𝑏𝑏𝑣𝑣) ≈ 0.7 𝑉𝑉
5. Design a Matlab function which will allow you to calculate pairs of parallel resistances which
give an overall resistance based on the E12 series of resistors.
You will use this program with the values calculated from design challenge 1-4 to determine your resistor pair values.
Information on the E12 series can be found at http://www.resistorguide.com/resistor- values/
Non-Matlab design aspects.
These design challenges do not require you to write Matlab code, but will provide your team with input information for your Matlab functions.
- Selecting battery chemistry
Refer to the document on MyLO which presents a preliminary comparison of battery chemistries. In addition to using this resource you should search for additional references on battery chemistry to help you make you decision.
Determine appropriate criteria for your design and justify your choice of battery chemistry.
- Interpreting the battery specifications
Based on the battery selected, consider the following questions- What is the nominal battery voltage?
- Look at the discharge graph on the datasheet to find the maximum charge, minimum
voltage, temperature limit and energy delivered
- Determine the minimum voltage at which the LED much be able to produce acceptable
light
- Make a recommendation on the solar panel voltage which would be needed to charge
the battery.
Extension:
- Predicting the operation time based on a particular level of battery charge
- Characterise your solar panel
Research how you could characterise your solar panel and prepare an experiment to conduct in the lab.
- Predict the time required for charging the battery under different sunlight conditions.
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