 | | Re: LEGO light sensor schematic
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(...) [snip] I'm happy to see that some of my concerns have been born out with these changes, it looks more like a happy little circuit now. (...) Are we sure that the photodiode is located in the schematic correctly? It doesn't look like its biased (...) (26 years ago, 3-May-99, to lugnet.robotics)
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| | Re: LEGO light sensor schematic
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Dennis Clark wrote in message ... (...) Your right. It just can't be the way it is drawn. I think it must be a photo transistor. Usually photo diodes are not as sensitive as photo transistors either. I'll touch up the circuit and see if it looks (...) (26 years ago, 4-May-99, to lugnet.robotics)
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| | Re: LEGO light sensor schematic
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Well if anybody still cares, I think the LEGO light sensor circuit is 100% correct now. The sensor is a phototransistor. Looking at the circuit implies a interesting side effect. If you shine a very bright light (ie laser pointer) into the (...) (26 years ago, 4-May-99, to lugnet.robotics)
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| | Re: LEGO light sensor schematic
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(...) Mike, Could it be that transistor 15 (I think), the one that is configured as a diode whose emitter is tied to the emitter on the output of the OpAmp potentially be some kind of non-linear negative feedback loop? Maybe to prevent oscillation (...) (26 years ago, 5-May-99, to lugnet.robotics)
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| | Re: LEGO light sensor schematic
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(...) Transistor 15 only has about .4V across it, so it is not operating in a very linear region. My best guess is that it helps make up for the drop in the follower 14 and provides some nonlinear gain. It tends to lower the gain for larger signals (...) (26 years ago, 5-May-99, to lugnet.robotics)
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