ELEC 242 Lab

Experiment 7.1

Assembling the System

Equipment

Components

Part 1: Position Sensor and Feedback Amplifier



Step 1:

 Wire the following summing amplifier circuit. $v_{dif}$ will be connected to the input of the motor amplifier, so consider this in choosing the loction on the breadboard. The pin numbers are for the interface board socket strip.
\includegraphics[scale=0.500000]{ckt8.1.ps}

This circuit forms the difference between the measured value of the shaft angle, represented by $v_{act}$ and the desired value $v_{des}$ . Using negative voltage for $v_{act}$ effectively subtracts it from positive $v_{des}$ . The 330k ohm resistor provides an offset so that we can use signals having zero average value (sine waves) to measure frequency response.

Question 1:

 Write an expression for $v_{dif}$ as a function of $v_{des}$ and $v_{act}$ . For $v_{des}$ =0, what is the range of $v_{dif}$ as $\theta$ is varied through its range?

Step 2:

 Get a motor-gearbox assembly from the cart. Use a C-clamp to clamp it to the edge of the bench with the spool hanging over the edge. The string should be wound clockwise around the spool (i.e. it should hang off the right side of the spool). We can consider this apparatus as either a model of an elevator or the prototype for a robot ice fisher.

Step 3:

 Plug a phone plug patch cable into J1-4 of the interface board. Plug the other end into the connector on the potentiometer on the motor-gearbox.

Step 4:

 By hand turn the spool counter-clockwise until it stops.

Step 5:

 Turn on the power supply. Measure the voltage $v_{act}$ . It should be 0 V.

Step 6:

 While watching $v_{act}$ turn the spool clockwise. It should gradually decrease.

Step 7:

 Turn the spool clockwise until it stops. $v_{act}$ should be about -5 V.

Part 2: Driving the Motor



Note
The connections for the motor are different from last week's circuit.


Step 1:

 Plug a phone plug patch cord into J1-6 on the interface board. Connect the other end of the patch cord to the 3-pin connector of the motor on the motor gearbox assembly.

Step 2:

 Ground one side of the motor (pin 8 on the interface board socket strip). Connect the other terminal of the motor (pin 9) to the motor amplifier output.

Step 3:

 Connect D/A channel 1 (pin 52) to the motor amplifier input.
\includegraphics[scale=0.500000]{ckt8.4.ps}


Step 4:

 Connect A/D input 5 (pin 47 on the interface board socket strip) to $v_{act}$ (pin 4 on the socket strip).

Step 5:

 Load and start the "Controller 1" Labview program.

Step 6:

 Turn on the power supply.

Step 7:

 Rotate the drum on the motor-gearbox. The value of Vact on the controller panel should change. Continue rotating the drum in the appropriate direction until Vact is about -2.5 V.

Step 8:

 Move the Drive Voltage slider upwards slowly until the motor starts to turn. The drum should turn counterclockwise and Vact should increase towards zero. If the drum turns clockwise, reverse the connections to the motor.