Ceramic Base SI Photodiode

rwgast_logicdesign

i found this realtively large photodiode

http://www.goldmine-elec-products.com/prodinfo.asp?number=G15405

the sales description makes it sound like a good deal, just wondering if anyone kmows what this would be used for, over a regular photodiode/transistor..

Mike Green

Look at the description of the device on the website whose link you provided. It's a "card / tape reader position sensor". It probably mounts along the edge of the track / groove for the tape or card with its long dimension parallel to the edge of the card or tape so that it's partially obscured by the tape or card. It's just a large photodiode whose output voltage is proportional to the light falling on it, so the voltage goes up if the card moves more off the device and the voltage goes down if the card moves more onto the device. This voltage is used to adjust the rollers or whatever is moving the card so that the card stays where it's supposed to stay.

The mounting is ceramic probably to resist wear from friction with the card or tape.

rwgast_logicdesign

thats kinda what i thought just wasnt sure. im kinda wondering if someone can think of a more creative use

Duane C. Johnson

Hi Mike;

Mike Green wrote: »

It's just a large photodiode whose output voltage is proportional to the light falling on it, so the voltage goes up if the card moves more off the device and the voltage goes down if the card moves more onto the device. This voltage is used to adjust the rollers or whatever is moving the card so that the card stays where it's supposed to stay.

Just a bit of nit pick:
The proportionality thing is highly linear not with voltage but with current.
I got several a couple of years ago. They work very nicely.

Duane J

Mike Green

Duane, you're absolutely right. Sorry.