When there is no obstruction to the beam the phototransistor conducts allowing the circuit connected to it to sense that the beam is not broken. There are two distinct states that this type of device can detect. The LED is always powered and emitting infrared light (invisible to the human eye). The sensor is in the shape of a horse shoe, an infrared LED is mounted in one half and a phototransistor is mounted in the other. This optical beam sensor (also known as an optical interrupt switch) is made up of two separate electronic units combined in one housing. The infrared beam sensor will be positioned around this last platter so make sure that the index hole is in a location that will trip the beam. The older drive had platters that were dark brown and not very reflective, the modern drive had platters that had a silver mirror finish.Ĥ) Drill index hole: Drill a ¼ inch hole near the edge of the 3rd platter. NOTE: The top platter that I ended up using was from a more modern drive. It was very easy to cut since it was made of aluminum. A grinder was then used to cut the grove. Cut a slot into the 1st platter, I clamped the platter into a vice protecting the surface with cardboard so it wouldn’t scratch. It could still work using a two platter drive but the top of the infrared beam sensor would be visible when a hand is over it.ģ) Cut Slot: Remove the screw in the center of the platters, this should allow the platters to be removed. And the third platter will have an index hole drilled into it, this index hole will be used to determine where the slot is when it is spinning. We will need three since the top one will have a slot cut into it, the second one will have a piece of white tape (or some other highly reflective material attached. The drive must spin counter clockwise.Ģ) Open Drive: Open the drive and see that there are three platters in the unit. STEPS TO CONSTRUCT CLOCKġ) Select Drive: Find an old hard drive that can spin up when power is connected, you may have to disconnect the 40 pin data cable to see that it can spin up. Custom programmed PIC16F628 microcontroller to control clock operation.īe informed when new projects are available or additional project information is posted by signing up to our mailing list.Three micro switches to set hours, minutes and seconds.Infrared Beam sensor and drilled index hole in lower drive platter.Minute hand is represented by blue light, hour hand is represented by red light and the second hand is represented by purple (both blue and red on at the same time).Slot cut into upper drive platter and white tape on center drive platter provides a slot that when illuminated by the LEDs will represent a clock hand.Uses 12 high power LEDs for displaying the clock hands, 6 Blue and 6 Red.For example the time is 2:30 the hour hand will be pointing at the 12 minute mark. The position of the hour hand is also dependent on the minute hand. The blue minute hand increments through each minute and the red hour hand increments through each hour. The purple second hand resets to the zero mark when it’s button is pressed. It is shown starting at 2:40:00.Īnother video (4.7MB) this one shows the clock time being set.Three buttons on the back allow clock adjustment. VIDEOS Watch a video (1.5MB) of the clock in operation!It takes the clock a sew seconds for the speed to stabilize, during this time there is a random pattern of lights that is displayed. The clock that is produced isn’t exactly practical since most hard drives (especially older ones) are too loud for a clock that is to operate 24 hours a day. You will need some electronic knowledge, some common electronic components and a bit of Have an old hard drive that no longer works? As long as it still spins up chances are you could build a clock out of your old hard drive! There are more pictures and videos below. The left image is the clock running in the dark, the one on the right is the clock at rest.
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