1. Advanced Design Applications UNIT 4: MANUFACTURING
STEMCenter for Teaching & Learning™ Engineering byDesign™
12/01/2009
Advanced Design Applications UNIT 4: MANUFACTURING
Learning Cycle Six – It’s NOT a Relay Race
TITLE SLIDE
© 2015 International Technology and Engineering Educators Association
© International Technology Education Assoc

2. STEMCenter for Teaching & Learning™ Engineering byDesign™
12/01/2009
Objectives
After completing this learning cycle, you will be able to:
Understand how relays work.
Create a working relay.
Construct a circuit using a commercial relay.
[Authors: Please include teacher notes appropriately.]
© 2015 International Technology and Engineering Educators Association
© International Technology Education Assoc

3. Electromagnetic Relays
STEMCenter for Teaching & Learning™ Engineering byDesign™
12/01/2009
Electromagnetic Relays
Used to switch things on and off
Available in a number of configurations
Control a wide variety of devices
Computers
Washing Machines
Refrigerators
Many manufacturing processes, as well as manufactured products, rely on the use of devices called electromagnetic relays to switch things on and off automatically. Electromagnetic relays are available in a number of configurations and are used to control a wide variety of devices such as computers, washing machines, refrigerators, dishwashers, and other automated systems. For example, in a dishwasher relays are used to turn on heating elements, activate sprays of hot water, illuminate lights on the outside of the unit, and control a number of other features required by the consumer. They are amazing and important device that operate quietly behind the scenes to do many things for us.
© 2015 International Technology and Engineering Educators Association
© International Technology Education Assoc

4. STEMCenter for Teaching & Learning™ Engineering byDesign™
12/01/2009
Relays
A small machine
Armature
Electromagnetic coil
Switch
Spring
Small amount of power to move armature to switch to a much larger amount of power
The basic concept behind relays is really pretty simple. A relay is a small machine consisting of an armature, an electromagnetic coil, a switch, and a spring. What relays do is connect two separate and completely independent circuits. The point of a relay is to use a small amount of power in the electromagnet to move an armature, which is able to switch a much larger amount of power. The spring holds the switch in one position until a current is passed through the coil. The coil generates a magnetic field which moves the switch. Relays can be activated by a very small amount of current and the switch can often handle a lot of current. For example, the electromagnet may be energized by 5 volts and 50 milliamps, while the armature can support 120 volts and 2 amps. So, basically you can control large power circuits with small power inputs.
© 2015 International Technology and Engineering Educators Association
© International Technology Education Assoc

5. STEMCenter for Teaching & Learning™ Engineering byDesign™
12/01/2009
Relays
All contain an electric coil powered by AC or DC
Generates magnetic force when energized
Magnetic force actuates or triggers switch
Relays action from one circuit to another by activating load circuit
Circuits don’t touch
Load circuit operates the device
The inner workings or a relay are best described by a model. All electromagnetic relays contain an electric coil powered by AC (alternating current) or DC (direct current). When the coil is energized, it generates a magnetic force that actuates or triggers a switch mechanism. The electromagnetic force relays the action from one circuit to another by activating the load circuit. These circuits, however, must not touch and do not become one continuous circuit. The load circuit is the circuit that operates the device such as a motor, light, or other relay.
A single pole (SP) contact means that all contacts in the relay connect in one position to a common contact. The term single throw (ST) contact means that the relay’s contact is open in one position and closed in the other. Single-pole, single-throw (SPST) relays can control only one load circuit. Study the flow diagram to get a better understanding of how single-pole, single-throw relays work.
© 2015 International Technology and Engineering Educators Association
© International Technology Education Assoc

6. STEMCenter for Teaching & Learning™ Engineering byDesign™
12/01/2009
Sensors
Information gathering technology
Heat sensors in ovens
Motion detectors in security systems
Thermostat controls in air conditioning
Float sensor on an automatic ice machine
In manufacturing, many types of machines and equipment have been developed to communicate information, transmit power, and interpret various conditions under which another machine must react. Machines gather information from many different types of sensors and then automatically (and often instantaneously) initiate the logic that has been stored within its memory (storage media).
Information-gathering technologies, such as sensors, are much more commonly used than you may think. For example, your home probably contains dozens, if not hundreds, of components and technologies that could be classified as sensors. Examples found in most homes include heat sensors in ovens and stoves, motion detectors in security systems or outside lights, the thermostat that controls the heating and cooling systems, and the float sensor inside an automatic ice maker that closes the water valve when the ice molds are full. Most sensors are relatively simple devices, yet when combined with machines, other sensory equipment, and networked with a primary processing system, sensors can accomplish some amazing tasks.
© 2015 International Technology and Engineering Educators Association
© International Technology Education Assoc

7. STEMCenter for Teaching & Learning™ Engineering byDesign™
12/01/2009
Exploration
Normally-closed sensors
Closed when not activated (turned on)
Open when activated (turned off)
Normally-open sensors
Open when not activated (turned off)
Closed when activated (turned on)
Depending on the type of device or sensor, the program may cause the opposite output than expected.
Normally-open sensors are open (not conducting, off) when you do not activate them and closed (conducting) when you do activate them (turn them on). Normally-closed sensors remain closed (conducting; on) when you do not activate them and open (off) when you do activate them. So, depending on the type of device or sensor (normally open or normally closed) you are using, the program may cause the opposite output than expected. If you have a normally-open sensor, ) will be open (off) and 1 will be closed (on). For a normally-closed sensor, 0 will be closed (on) and 1 will be open (off).
© 2015 International Technology and Engineering Educators Association
© International Technology Education Assoc

8. Piezo Vibration Sensor
STEMCenter for Teaching & Learning™ Engineering byDesign™
12/01/2009
Piezo Vibration Sensor
A piezoelectric sensor is a device that uses the piezoelectric effect, to measure changes in pressure, acceleration, strain or force by converting them to an electrical charge.
© 2015 International Technology and Engineering Educators Association
© International Technology Education Assoc

9. STEMCenter for Teaching & Learning™ Engineering byDesign™
12/01/2009
Photo Resistor
A photoresistor or light-dependent resistor (LDR) or photocell is a light-controlled variable resistor. The resistance of a photoresistor decreases with increasing incident light intensity; in other words, it exhibits photoconductivity.
© 2015 International Technology and Engineering Educators Association
© International Technology Education Assoc

10. STEMCenter for Teaching & Learning™ Engineering byDesign™
12/01/2009
Temperature Sensor
These sensors use a solid-state technique to determine the temperature. They use the fact as temperature increases, the voltage across a diode increases at a known rate.
© 2015 International Technology and Engineering Educators Association
© International Technology Education Assoc

11. STEMCenter for Teaching & Learning™ Engineering byDesign™
12/01/2009
Boolean Logic
The AND Function
Requires both sensors to be either activated or closed for output to be activated.
As circuits get more complex, it becomes necessary to manage the logic of the circuits outputs. Boolean logic is often embedded into programs designed to control the outputs of a circuit. An understanding of Boolean logic is essential for programming the BS2 with multiple sensors.
The AND function requires both sensors to be either activated or closed in order for the output to be activated. As illustrated in the schematic below, both A and B sensors (input) have to be closed for the light (output) to be turned on. Another way to understand the AND function is through a truth table. This uses binary notation in a truth table to illustrate the AND function. 0 represents de-energized or open and 1 represents energized or closed.
© 2015 International Technology and Engineering Educators Association
© International Technology Education Assoc

12. STEMCenter for Teaching & Learning™ Engineering byDesign™
12/01/2009
Boolean Logic
The OR Function
Requires only one sensor to be activated or closed for the output to be activated.
The OR function requires only one sensor to be activated or closed for the output to be activated. Both sensors will also activate the output. As illustrated in the schematic, the light (output) will be turned on by activating one or both sensors (inputs). The truth table shows the same thing.
© 2015 International Technology and Engineering Educators Association
© International Technology Education Assoc