Test #1 (Advanced Surfacing - IR Comm’s - Programming & Gears).pdf

Test #1 (Advanced Surfacing - IR Comm’s - Programming & Gears) (50) Marks Total (32) Short Answer (All topics: Advanced Surfacing Tool, Arduino IDE, IR Comm’s, Gears (7) Circuit + Code - Describe what will hap[en based on specific actions (11) Four different gear questions two, three, four gears L...

Test #1 (Advanced Surfacing - IR Comm’s - Programming & Gears) (50) Marks Total (32) Short Answer (All topics: Advanced Surfacing Tool, Arduino IDE, IR Comm’s, Gears (7) Circuit + Code - Describe what will hap[en based on specific actions (11) Four different gear questions two, three, four gears Lesson 1: IR (Infrared) Communication Basics - Inexpensive way to transmit information - Infrared light is an electromagnetic wave - Infrared light has a slightly longer wavelength making it invisible to the human eye - IR communication is typically limited to small areas using low intensity LED transmitters - One limitation of IR communication systems is that they are line of sight systems - Line of sight systems: must be a clear path between the transmitter and the receiver for the communication to work - Depending on the strength of the IR signal and the surface quality of adjacent surfaces the IR signal can bounce off surfaces so they reach the receiver - Typical IR transmitters work reliably in the range of up to 5m or 15ft - Increasing current of the eLED will increase intensity of the IR signal - Safe current of 20mA - IR signals have a carrier frequency with a typical duty cycle of 50% - IR communication systems consist of two components - the transmitter and the receiver - Due to low power requirement the transmitter is small, battery operated and have a significant battery life making it very convenient Signal Modulation - To prevent false signals the IR signals are typically transmitted at specific carrier frequency - Commercial Ir carriers frequencies are in the range of 10-50 Khz with 38kHz being very common.  - lookin g closer at the ON blocks that they aren’t ON 100% of the time but pulsing on and off at the rate of the carrier frequency which is 38,000 times a second IR Reciever: - Picks up infrared signals and is filtered to only respond or relieve infrared light at the specified carrier frequency - Made up of a photodiode connected to a bandpass filter and amplifier - Base signal frequency is fast and can turned off between 1 - 3 ms range creating the ON/OFF blocks and the binary signal that is transmitted on top of the carrier frequency Major advantage of IR communication: - Speed of up to 12.5 gigabits per second are possible for short distances a few feet - Speed of up to 1 gigabit per second for long distances up to 30 meters IR Protocol Basics: - IR communications follow a variety of protocols - The language or structure for the IR communication - Start code - Address Code - Command Code - Start Code - indicates a message will follow and triggers the listening phase so the full message is received - Address code - indicates which device the code is being sent to in effect it multiplies the number of communication codes you can use - Command code - represents the button that was pressed or the instruction to be completed - NEC protocol - includes code sent in reverse which can be used to verify what was received and improve the accuracy of communication Repeat Codes: - Repeat code - instead of sending a continuous signal if any button is held for more than approximately 40ms the repeat code will be sent out until the code is released - Last button code must be stored and used while the repeat code is active the absence of a code should trigger the command to stop Lesson 2: The Switch Statement Switch Statement - a conditional statement closely related to the if/elseif statement - Conditional statement are most powerful programming statements as they allow for multiple outcomes based on logic - Switch statement evaluates an expression against multiple cases and executes or one or more blocks of code based on matching cases An example of a switch statement with two case statements and a fall back known as the default - The expression is a variable and its value is compared against each case - The first case is tested against the expression if it matches the attached code block that it will execute once the code executes the break command ends the switch block - If the first case does not match then the expression goes against the second case and will execute fif matching and then executes break command and ends the switch block. - Continues for all cases - If none of the cases match than the default code can added and end the switch code block - Button press is received and sent to a library and can be accessed using “results.value” Switch vs If Else: Battle Switch If Else Efficiency More efficient where are many cases or possible outcomes to be evaluated (if more than 5 cases typically use switch statements What are you evaluating? Excellent for evaluating fixed If else if statements are better data values such as suited for evaluating logic comparing the value of a expressions resulting in a variable to a number of boolean value (In JAVA) possible results. Speed Executes faster especially when there are many expressions to evaluate to get to the core of a series f nested if statements Clarity & Troubleshooting Much easier to read and troubleshoot especially where are many possible outcomes Lesson 3: Gears - They transfer rotational motion between gears of different sizes, controlling the direction, speed, distance, and torque through the design of the gear - Used by humans for about 4000 years - Old versions of gears which were more simpler suffered vibration, wear, and other problems - One of the oldest examples of gear machines date back to 2000 BC - The antikythera Mechanism, which was used to predict the movement of the sun, moon and major planets and was made up of 30 complex gears Tooth Shape: - Involute tooth - Face of an involute is an involute of a circle - Helps solves problems - Line of action or pressure line - maintains a constant radius and therefore constant gear ratio through the mesh - Constant ratio achieved is good because the gear moves at constant speed and this eliminates vibration and reduces friction and wear Types of Gears: Rack and Pinion: - Turns rotational motion into linear motion was commonly used for automotive steering Helical: - Tooth shape allows mesh in a parallel or crossed orientation - Advantage: - The area of contact between teeth gradually increases then decreases through each mesh creating a quieter and smoother gear for high speed applications Worm: - Transmits rotational motion into rotational motion on a crossed or perpendicular axis Bevel: - The bevel gear also transmits rotational motion into rotational motion on a crossed or perpendicular axis Pitch Diameter (Circle) - Diameter of gear at mid-point of contact Circular Pitch - distance between teeth at point of contact Pressure angle - the angle between the tooth face and the gear wheel tangent (commonly 20 degrees) Clearance - distance between top land and bottom land of mating gears Backlash: - Cannot manufacture perfect parts - Some allowed tolerance or space between mating parts to ensure they fit - When gear reverse direction backlash occurs as the moving gear slams into the stationary gear due to the extra tolerance Efficiency: - 3 - 5% power loss for every gear mesh interface - Occurs due to friction at the gear face and bearings - Surface finish of the gear effects gear efficiency smoother teeth = more efficient teeth Lubrication: - Gear must be lubricated to maintain efficiency and decrease tooth wear Cyclical Loads and Heat Stress: - Gears that are subjected to a wide range of loading (high or low) and wide range of temperature (hot and cold) will have a reduced life Torque limit: - There is a maximum limit over which the gear will fail destroying the gear set increasing the gear thickness will increase the torque limit Maximum Ratio - 6:1 maximum recommended ratio per stage for a spur (involute) gear Advancing Surface Tools: (7 tools) - making a grid Smoove Tool - raising parts of the grid - contour lines - creates new surface with non-coplanar edges - generate soap skin tool - generate soap bubble tool - changes pressure and bulge https://www.revisely.com/quiz/HVZws