Technical understanding part 3 - Revision history

Stcd11: Added video

2024-02-19T11:54:43Z

Added video

Stsb11: /* Sensors to measure rotational speed */

2024-01-23T08:36:08Z

Sensors to measure rotational speed

Stcd11: Added video

2024-01-19T14:20:25Z

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Stsb11: /* 6.4d Demonstrate an understanding of networking and of communication protocols, such as: */

2023-04-26T08:10:08Z

6.4d Demonstrate an understanding of networking and of communication protocols, such as:

Stcd11: Added pneumatic images

2022-06-17T12:28:45Z

Added pneumatic images

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2022-06-14T10:16:06Z

spelling

Stcd11: edited question

2022-06-14T10:15:36Z

edited question

Stcd11: Added exam style question

2022-06-14T09:59:52Z

Added exam style question

Stcd11: Added video

2022-02-21T11:21:55Z

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Stsb11: /* 6.4d Demonstrate an understanding of networking and of communication protocols, such as: */

2021-11-29T10:50:35Z

6.4d Demonstrate an understanding of networking and of communication protocols, such as:

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 [[File:52_DCV_valve.gif|500px|thumb|center]]
 <center><youtube>hmz1h5fk2bI</youtube></center>
 #In a pneumatic circuit, restrictor valves can be used to control cylinder speed by slowing the speed at which air can travel through an air-line. To read more about flow restrictors and the many different types and how they work, click [http://www.hydraulicspneumatics.com/200/TechZone/HydraulicValves/Article/False/6409/TechZone-HydraulicValves here].

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 ===Sensors to measure rotational speed===
-#There are a number of ways to measure rotational speed, the most common being an instrument called a <i>tachometer</i>. A tachometer (revolution-counter, tach, rev-counter, RPM gauge) is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays the revolutions per minute (RPM) on a calibrated analogue dial, but digital displays are increasingly common - you can see tachometers in the rev-counter in a car. In the diagram below, you can see that as the input rotates faster, the fly-weights are spun faster and the resulting force causes the coil-spring to be increasingly compressed. This leads to the output 'needle' moving further to the right.
+#There are a number of ways to measure rotational speed, the most common being an instrument called a <i>tachometer</i>. A tachometer (revolution-counter, tach, rev-counter, RPM gauge) is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays the revolutions per minute (RPM) on a calibrated analogue dial, but digital displays are increasingly common - you can see tachometers in the rev-counter in a car.
 [[File:tachometer.jpg|500px|thumb|center]]
 <center><youtube>Ndq-IoF2o9Y</youtube></center>
-#You can create your own instrument to measure rotational speed in a lab, such as:
+#Designing systems to measure RPM is a popular exam topic as many electromechanical systems use the rotary motion of a motor to drive a system and precise speed is often important. You can create your own instrument to measure rotational speed in a lab, such as:
 ##Electro-magnetic systems. A small magnet can be mounted on a disc connected to a rotating shaft. A reed switch can be placed in the path of the magnet so that once per revolution, the switch is closed momentarily as it passes. This can be connected to a microcontroller which can count the number of times the switch is closed per minute and display this to the end-user. As this approach uses a mechanical part (the reed switch) which takes a few milliseconds to open and close, the system won't be able to accurately record very high speed rotation.
 [[File:electromag_tachometer.gif|500px|thumb|center]]

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 <center><youtube>GhS1qpHoSX0</youtube></center>
 [[File:52_DCV_valve.gif|500px|thumb|center]]
 #In a pneumatic circuit, restrictor valves can be used to control cylinder speed by slowing the speed at which air can travel through an air-line. To read more about flow restrictors and the many different types and how they work, click [http://www.hydraulicspneumatics.com/200/TechZone/HydraulicValves/Article/False/6409/TechZone-HydraulicValves here].

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 ##SMTP (Simple Mail Transfer Protocol) is used for the sending of email.
 ##FTP (File Transfer Protocol) is a protocol used for transferring files from one computer to another over the web.
-#<strong>Radio-frequency identification (RFID)</strong> Works when a microchip inside the ticket receives power by electromagnetic induction from a radio frequency field generated by the reader unit, and it responds by sending a unique identifier code by radio back to the reader unit. Unlike a barcode, the tag need not be within the line of sight of the reader, so it may be embedded in the tracked object.
+#<strong>Radio-frequency identification (RFID)</strong> Works when a very small microchip (e.g. inside a ticket, a sticker or under a packaging label on food purchased in a supermarket) receives power by electromagnetic induction from a radio frequency field generated by the reader unit, and it responds by sending a unique identifier code by radio back to the reader unit. Unlike a barcode, the tag need not be within the line of sight of the reader, so it may be embedded in the tracked object.
 [[File:rfid_system.gif|500px|thumb|center]]
 #<strong>Near-field communication (NFC)</strong> Similar to RFID in which data is transferred through a short range (4cm) radio field. NFC tickets can be passive (they receive energy from the radio field) or active such as a mobile phone running a payment app.
 [[File:nfc_comms.jpg|500px|thumb|center]]
-#<strong>Bluetooth</strong> is a wireless technology standard for exchanging data over short distances from fixed and mobile devices, and building personal area networks (PANs). In order to exchange data
+#<strong>Bluetooth</strong> is a wireless technology standard for exchanging data over short distances (up to 2-3m reliably) from fixed and mobile devices, and building personal area networks (PANs). In order to exchange data, the devices first need to be 'paired'. This is commonly used in mobile phones for connecting to speakers (e.g. to stream music and car-kits to import contacts/connect to the web).
 #<strong>Wi-Fi</strong> most commonly uses the 2.4 gigahertz and 5GHz radio bands. Anyone within range with a wireless modem can attempt to access the network; because of this, Wi-Fi is more vulnerable to attack than wired networks. Wi-Fi Protected Access (WPA2) is a security technology created to protect information moving across Wi-Fi networks by encrypting data that is transmitted to prevent malicious 3rd parties from reading it.
 #<strong>Embedded devices</strong> are computer systems integrated into a product. It is embedded as part of a complete device often including hardware and mechanical parts. Embedded systems control many devices in common use today, such as calculators and microwave ovens.

← Older revision		Revision as of 12:28, 17 June 2022
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	Sketch a system which will send a '''single-acting''' cylinder positive (extend) '''slowly''' when '''two''' push actuators are pushed at the same time. As soon as either actuator (or both actuators) is released, the cylinder should immediately go negative (retract) '''slowly'''. [6 marks]		Sketch a system which will send a '''single-acting''' cylinder positive (extend) '''slowly''' when '''two''' push actuators are pushed at the same time. As soon as either actuator (or both actuators) is released, the cylinder should immediately go negative (retract) '''slowly'''. [6 marks]
		+	# This solution requires an AND configuration, see image below:
		+	[[File:ANDpneumatic.png\|500px\|thumb\|center]]
		+	# Here is an example of an OR configuration:
		+	[[File:ORpneumatic.png\|500px\|thumb\|center]]

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 Exam style question:
-An engineer wishes to design a system to bend a steel bar 30 degrees using pneumatic cylinders and valves. They are concerned for the operator’s safety, so wish to ensure that they place both hands on push actuators before the cylinder is activated in order to ensure their hands are not accidentally crushed.
+An engineer wishes to design a system to bend a aluminium bar 30 degrees using pneumatic cylinders and valves. They are concerned for the operator’s safety, so wish to ensure that they place both hands on push actuators before the cylinder is activated in order to ensure their hands are not accidentally crushed.
 Sketch a system which will send a '''single-acting''' cylinder positive (extend) '''slowly''' when '''two''' push actuators are pushed at the same time. As soon as either actuator (or both actuators) is released, the cylinder should immediately go negative (retract) '''slowly'''. 		[6 marks]

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 #In a pneumatic circuit, restrictor valves can be used to control cylinder speed by slowing the speed at which air can travel through an air-line. To read more about flow restrictors and the many different types and how they work, click [http://www.hydraulicspneumatics.com/200/TechZone/HydraulicValves/Article/False/6409/TechZone-HydraulicValves here].
 ===Sensors to measure rotational speed===
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 #An ultrasonic distance sensor can be used to measure objects up to around 3m away. These work by producing an ultrasonic 'click'. As we know the speed of sound, the time taken for the click to bounce off the surface being measured and for its echo to be detected can then be used to calculate the distance.
 #IR distance sensors can be used over shorter ranges (up to about 80cm), and can also approximate distance. As sunlight can interfere with their operation, they can't be used in bright conditions.
 #You can read more about distance sensors [https://www.maxbotix.com/articles/ultrasonic-or-infrared-sensors.htm here].
 ==6.4d Demonstrate an understanding of networking and of communication protocols, such as:==