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Electronics => Electronics => Topic started by: joe61 on October 10, 2011, 07:21:21 AM

Title: LED detector
Post by: joe61 on October 10, 2011, 07:21:21 AM

I've been looking for a component that combines the "remote control" type IR receiver, with an IR phototransistor. The idea is to get range data using the 38KHz modulation to avoid interference with ambient light.

So a "remote control" type receiver like this http://www.vishay.com/ppg?82090 (http://www.vishay.com/ppg?82090) returns a series of digital signals - the control code. A phototransistor just senses light and gives an analog signal back. I'd like to have the analog signal and the 38KHz modulation. Is there such a beast?

Thanks

Joe

Title: Re: LED detector
Post by: Soeren on October 11, 2011, 05:09:35 PM

Hi,

Quote from: joe61 on October 10, 2011, 07:21:21 AM

I've been looking for a component that combines the "remote control" type IR receiver, with an IR phototransistor. The idea is to get range data using the 38KHz modulation to avoid interference with ambient light.

So a "remote control" type receiver like this http://www.vishay.com/ppg?82090 (http://www.vishay.com/ppg?82090) returns a series of digital signals - the control code. A phototransistor just senses light and gives an analog signal back. I'd like to have the analog signal and the 38KHz modulation. Is there such a beast?

Not as a simple integrated device, but there are a few options...
1. Find a trashed TV or similar (dated from the late seventies to the early nineties) and liberate the IR receiver part, usually encapsulated in a small metal box with a number of connecting pins/wires).
2. Find, if possible, one of the IR receiver chips from around the same time period - Siemens made some (only one I remember the exact number for of the top of my head is TDA4050, but they made several IIRC) and Sony made one starting with something like "gu" or something close.
3.  Build the equivalent of a TSOPnnnn with discretes.

For the first two options, you'll have to poke around a bit to find the AGC voltage, which will be your range signal. The reflectance ratio of the obstacle that it sees will change the distance reading unfortunately.
It's (mainly) the AGC that makes an integrated IR-receiver able to cope with distances from ~10cm to ~30m (when used for the intended purpose).