Home project - remote controlled projection screen

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The front limit switch, limits how far the system goes forward. It's long metal tongue was twisted slightly so it's pushed at the right location.
The rear limit switch, used to indicate when the DC motor should be stopped.
IR object detector, it has one modulated light emitter and one receiver in the same unit. On the screen I have attached to small bits of photo slide masking tape, which has one side designed to reflect the light. This increases the effectiveness of the IR detector. By carefully positioning the detector, it detects precisely when the masking tape is in front.
The microcontroller is a Parallax Stamp Controller Interface Board (right), coupled with an Opto22 8 Channel I/O module rack. The latter has two optocouplers relays to turn on/off the power to the AC motor controlling the projection screen.
This small 12V switching power supply is great for the job. It powers the boards and the DC motor.
This Jameco DC motor is small, but has sufficient torque to move the whole system horizontally. I mounted everything in a $18 aluminum box from Fry's, in which I drilled holes to attach the various components.