Instrumentation Project: Threshold Actuator Application: Conveyor Belt systems, Garage door Automation and more.

1. INTRODUCTION
Threshold Actuator
Abhimanyu Sehrawat, Matei Iliescu Stieghelbauer
Department of Mechanical Engineering, Lassonde School of Engineering, York University
*Final project for MECH2502: Instrumentation and Measurement Techniques (Winter 2016)
SENSOR(S) OPERATING PRINCIPLE
• Goal of the system : To actuate the DC servo-motor in set direction in response to
the applied weight cut-off sensed force sensing resistor.
• Significance/importance: The machines in manufacturing environment(such as
conveyor belt) need to lift up the weight and carry those by rotations. Hence, in
order to conserve the mechanical energy of the machine , efficiency of tasks
performed in regards to safety is prime motive.
• Potential real-world applications: - Manufacturing plants(iron –ore processing)
• Garage door operation ( Parking application)
• Food processing factory (Weight sensing Various zones Packaging Export)
• Bridge/construction mechanisms ( Desired movements of mechanical arms can be
done as per weight sensed).
RESULTS
METHODOLOGY
REFERENCES
CONCLUSION
• The system runs accurately using 310g of weight. A short coming of the system is
that it would have to be scaled up for use in manufacturing or garages due to the fact
that the sensor can only support up to 2.2 lbs.
• One improvement could have been to use two force sensors with regards to garage
applications. One sensor would sense when the car is on the parking lot and triggers
the garage door to open and the other sensor to sense when the car is safely in the
garage and close the door. This way there is no timer that closes the door which
could be a potential hazard if the car takes too long to enter the garage.
• Calibration curve
Experimental results :
The following run was tested if the
weight of the car is greater than 250
grams. The shown image highlights the
end stage of the parking when the car
has successfully parked inside and went
off the sensor.
Weight Used: 3 blocks(310 grams.)
• The current block represents the volts
for current weight on the sensor.
• The calculated block contrasts the volts
calculated from sensor calibration equation
[here, 0 V => no car => Door closed(Red)]
• When current voltage is above 3.01V, i.e.
car is over sensor.
Thus, following procedure executes:
• Door will open(DC servo rotates clockwise).
• Enter sign lit up.
• The door will close(DC servo moves back in position) after waiting for 5 seconds when
the current output drops below 3.01V.
• The red sign goes on when the car is moving in and upon door closure.
Observations:
• The calibration results matched with the provided standard curve for 10 Kilo-ohms
resistor. Although, the logarithmic fit for curve line was similar to the cubic fit .But,
greater R^2 closer to 1 was used. The calibration was done using the absolute weight of
the blocks otherwise, sensor won’t respond accurately.
• The DC servo motor inherits the relative position of it from last point. Hence, the
rotation was still 180 degrees but at different positions. The DC servo couldn’t provide
the constant velocity as well.
• Rationale for selecting Force Sensing Resistor (FSR): The physical property sensing
involved here is the weight which is used set a standard threshold for the DC Servo
motor to respond. FSR senses the weight above contact area by changing the
resistance and provides a relation between Force and resistance. With the application
of force/weight , the element inside FSR contracts and reduces the resistance.
• System Design with schematics/pictures of the system
Figure(a.) System with all components
• Role of components:
• LM324 Op-amp: Amplifies the output voltage of FSR
by providing enough gain to make it detectable by
Q8-Quanser DAQ.
• Resistor: 10Kilo-ohms integrates with LM324 for
purpose of gain in output.
• Weight: 103.8 grams(5 blocks) used for calibration
and as force for the sensor
• DC Power Supply (15V and 5V): The power supply of 14.7V provided across the op-amp
and 5VDc across the FSR as it operational voltage.
• Voltage amplifier: Amplifies the signal sent by the DAQ and forward it to the Servo-
motor
• DAQ: Interface between the breadboard output, LabVIEW and the amplifier which
regulates the voltage in analog systems for a given sampling rate(1000Hz).
• Servo-unit: Receives the amplified voltage output from the amplifier and rotates the
beam mounted on top with respect to the polarity of the voltage(-ve: Anti-Clockwise,
+ve: Clockwise)
• LabVIEW scripting: The LabVIEW code was written focusing on the execution loop
regulating every action such as sensing, rotating servo motor, wait time and providing
indications. It accommodates the cubic calibration equation and the current output is
compared with the calculated value for loop executions. Corresponding conditions were
imposed in order to achieve the accurate functioning of garage door operation.
Figure c. Interface signifying the DC-Servo
and FSR mechanism
Figure d. LabVIEW block diagram
(1) Beckwith, Marangoni, Liehard V (2007): Mechanical Measurements (6th Ed), Pearson.
(2) Tabatabaei, Nima. "MECH2502 Lab Manual 3-4." Instrumentation and Measurement Technique. York University,
3 Feb. 2016. Web. 4 Apr. 2016..