# hw8 - condition(5 marks Speed = 1200 rpm Fig 1 2 A design...

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The Hong Kong Polytechnic University Department of Mechanical Engineering 2008/09 Semester 1 ME4204 Mechatronics Systems Assignment 2 Name: Student ID: Notes: 1. Please answer all the following questions. 2. Submission Deadline: 1 November, 2008 3. Submission Methods: Either a. Hand in during lecture (Print-out), Or b. Email to [email protected] (PDF format). 1. A 50 V, d.c. shunt motor drives a constant-torque load at a speed of 1200 rpm as shown in Fig.1. The armature and field resistances are 2 Ω and 100 Ω , respectively. The motor draws a line current of 15 A at the given load. (a) Calculate the resistance that should be added to the armature circuit to reduce the speed by 25%. (10 marks) (b) Assume the rotational losses to be 80 W. Calculate the efficiency of the motor without and with the added resistance. (10 marks) (c) Calculate the resistance that must be added to the armature circuit to open the motor at the holding

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Unformatted text preview: condition. (5 marks) Speed = 1200 rpm Fig. 1 2. A design engineer is designing a robotic toy which involves analog-to-digital (AD) conversion and digital-to-analog (DA) conversion. For the AD conversion, he needs to determine the following: (a) The smallest step size (resolution) of an 8-bit ADC in the range of − 5 V to +5V. (3 marks) (b) The number of bits required for an ADC which has a range of 5V and a resolution of 5 mV. (3 marks) (c) The conversion time for a 12-bit ADC with a clock frequency of 1 MHz. (3 marks) (d) The digital output code of 7.5V if an 8-bit ADC with a 0V to 10V range is used for the purpose of sampling the voltage of an analog sensor. (3 marks) For the DA conversion, he needs to determine the following: (e) The resolution of a 4-bit R − 2R DAC as shown in Fig. 2 if the reference voltage is 5 V. Fig. 2 END...
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hw8 - condition(5 marks Speed = 1200 rpm Fig 1 2 A design...

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