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Step 9Build the Rotational Sensor Rig
The rotational sensor rig is a "U" shaped block that holds the infrared emitter and photo-transistor in place. I made mine out of wood, but any material should work fine.
My measurements are based on my hard drive chassis. Make sure to measure your platter height with respect to the floor of the chassis. Use a piece of paper, and mark the platter height with a pen. This way, you can accurately measure with a ruler.
The platter in my rig is 1/2" above the chassis. The design of my sensor rig is based on this height. Adjust as neccessary.
Grab a piece of 1/2" thick wood, and cut out a 1" by 1-1/2" rectangle. Cut out a notch from one side, 3/4" deep and 1/4" from the top and bottom. Mark a point on the top a 1/4" from the side and front. Use this point to drill a 3/16" diameter hole through the entire block. A drill press will keep the hole straight through both sections.
Once you have finished making the rig, test fit it within the chassis, making sure the platter can spin freely. Push the emitter and photo-transistor into either hole, and test fit the rig in the chassis again. Make sure the platter can spin freely. Once you are happy with your rig, proceed to glue the emitter and photo-transistor in place.
My measurements are based on my hard drive chassis. Make sure to measure your platter height with respect to the floor of the chassis. Use a piece of paper, and mark the platter height with a pen. This way, you can accurately measure with a ruler.
The platter in my rig is 1/2" above the chassis. The design of my sensor rig is based on this height. Adjust as neccessary.
Grab a piece of 1/2" thick wood, and cut out a 1" by 1-1/2" rectangle. Cut out a notch from one side, 3/4" deep and 1/4" from the top and bottom. Mark a point on the top a 1/4" from the side and front. Use this point to drill a 3/16" diameter hole through the entire block. A drill press will keep the hole straight through both sections.
Once you have finished making the rig, test fit it within the chassis, making sure the platter can spin freely. Push the emitter and photo-transistor into either hole, and test fit the rig in the chassis again. Make sure the platter can spin freely. Once you are happy with your rig, proceed to glue the emitter and photo-transistor in place.
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Dec 9, 2008. 4:22 PMJimwright
says:
I ripped open a 3 1/2" floppy drive and found a LED / sensor. (Lots of them in printers too, as I recall.) It even had a diagram on the back of the pcb that matched the schematic here. I rigged it up with the 270 and 10K resistors, and it put out a great 4.7V when the gate is blocked. What's nice about it is that it's very compact (and free).
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