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group2:electrical_design 2008/12/09 15:45 group2:electrical_design 2008/12/09 16:28 current
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====== Electrical Design ====== ====== Electrical Design ======
-he PIC16F818 microcontroller will be used to control the stepper motor, acquire data, and send it to a laptop via a serial interface. The stepper motor has a permanent magnetic core, which is arranged in alternating north-south “pie slices”. The picture below shows what this core looked like, along with the two coils which rotate it. When a current is applied the magnets will be attracted to the coil, depending on the direction of the current. By altering these currents in a specific fashion, it is possible to get the motor to rotate in discreet steps.+The PIC16F818 microcontroller will be used to control the stepper motor, acquire data, and send it to a laptop via a serial interface. The stepper motor has a permanent magnetic core, which is arranged in alternating north-south “pie slices”. The picture below shows what this core looked like, along with the two coils which rotate it. When a current is applied the magnets will be attracted to the coil, depending on the direction of the current. By altering these currents in a specific fashion, it is possible to get the motor to rotate in discreet steps.
{{:group2:coil.jpg|}} {{:group2:coil.jpg|}}
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-The transistors in the above diagram are operated as a switch: when the base is saturated, it makes a path across the collector-emitter junction, and when it isn’t, this path is closed. The resistance of t[[http://example.com|External Link]]he stepper motor is 16.7Ω. With 5V supplied each coil draws 0.3A of current. A power transistor must be used in order to avoid damage to the equipment. The output of the micro controller is not enough to saturate the power transistors, and so a second set of regular transistors will be used to amplify the microcontroller output and saturate the power transistors. One regular transistor will be used to saturate transistors 01 and 04, a second one to saturate transistor 02 and 03, a third one to saturate transistors 05 and 08, and a fourth one to saturate transistors 06 and 07. +The transistors in the above diagram are operated as a switch: when the base is saturated, it makes a path across the collector-emitter junction, and when it isn’t, this path is closed. The resistance of the stepper motor is 16.7Ω. With 5V supplied each coil draws 0.3A of current. A power transistor must be used in order to avoid damage to the equipment. The output of the micro controller is not enough to saturate the power transistors, and so a second set of regular transistors will be used to amplify the microcontroller output and saturate the power transistors. One regular transistor will be used to saturate transistors 01 and 04, a second one to saturate transistor 02 and 03, a third one to saturate transistors 05 and 08, and a fourth one to saturate transistors 06 and 07.

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