Subject:
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Re: LEGO light sensor schematic
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 5 May 1999 04:38:44 GMT
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Viewed:
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969 times
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In lugnet.robotics, Michael Gasperi writes:
> 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 phototransistor it will take current away from the LED and
> make it go off. I tried it and it works. It is of no real value, but it does
> further confirm things. Thanks for all your help fixing it up.
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 of the circuit?
just wondering,
DLC
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Message has 1 Reply:
 | | 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 (...) (25 years ago, 5-May-99, to lugnet.robotics)
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Message is in Reply To:
| | 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 (...) (25 years ago, 4-May-99, to lugnet.robotics)
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