Optical Keyswitches

General Description

The most likely candidates for optical keyswitches are called reflective object detectors. They include a photo-diode and an infrared LED embedded in IR transmissive resin, and mainly seem to be used for detecting the opening and closing of doors.

Parts Selection

The most suitable sensor seems to be the Optek OPB607A. It is relatively inexpensive, comes with a package that will be easy to orient, has a nice linear region in its current response, and has a relatively long range. E-mail Drew if you want one to tinker with; he has a few on hand.

Drew's part search notes:

OPB607A. Used by the ECE110 lab. Cubical package. About $1.39 each. 50% at 0.25", with nice linear response.
LED: 1.7 V at 20mA

OPB730F Round package. Darlington.

Fairchild Semiconductor
QRD1313 $0.83 PCB straight pins. Darlington output. 50% at around .280 inches
QRE00034 6.2mm 50%, about .24" Funny package. Price?
QRB1114 Funny Package $1.01. Also 50% about 80 mils = 2.03mm
QRB1133, QRB1134 funny package, on 24" of wire. Transistor output. 50% around .28"
QRE1113GR $0.50 Cheap! Surface mount. 50% about 80 mils.
QRD1114 $0.83 Phototransistor output. 50% about 80 mils.
QRD1113 $0.83 Phototransistor output. 50% about 80 mils.
QRB1113 50% at about 80 mils = 2.03 mm

Paul V.'s Notes:

The Kodenshi SG-107F3 is a similar reflective photosensor, but smaller than the OPB607A. In Jan 2005 I purchased 1,000 units for $0.30 each from Kodenshi America in San Diego, 858-268-4316. Kodenshi makes several variations, including a surface-mount package.

The Sharp GP2S27C is similar to the Kodenshi SG-107F3, but surface-mount. At present I have ~200 of these which I would be happy to sell for $0.30 each (I paid over $1 each for them). Samples on request.

U.S. Patent 5,001,339 is abandoned (according to PatentMonkey.com). 5,231,283 will expire on 7/27/2010. These are excellent patents. Gulbransen's "Nessie" system used transmissive photosensors, which tend to be more expensive than the subminiature reflective type. However, the software detailed in the '283 patent can be used with a reflective sensor as well.

I spoke with a guy at Gulbransen approx. 12 years ago. He said at that time that they had no interest in their product which these patents protected. To my knowledge, this product has not been for sale for a long time. I doubt very much that they would care if a few people infringed the '283 patent today. It simply wouldn't be worth the time and cost of an infringement suit, in my opinion.

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