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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Mon, 3 May 1999 19:37:48 GMT
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Viewed:
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961 times
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In lugnet.robotics, Michael Gasperi writes:
> In lugnet.robotics, lego-robotics@crynwr.com writes:
[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.
> > Is the detector a photo diode or a photo transistor?
>
> I think photo diode used in photovoltaic mode. It looks like it pushes the
> voltage down from that established by the LED.
Are we sure that the photodiode is located in the schematic correctly?
It doesn't look like its biased on. The voltage readings are consistant,
or pretty close to, what I would believe is a forward biased diode. Is it
not biased 'on' normally and we are waiting for a negative voltage to appear
there?
I have to agree with one of your previous comments. This seems hopelessly
complex for the job it needs to do...
thanks,
DLC
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Message has 1 Reply:
 | | 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 (...) (25 years ago, 4-May-99, to lugnet.robotics)
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Message is in Reply To:
| | Re: LEGO light sensor schematic
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| (...) OK, I fixed that and in the process discovered they should be PNPs. 3Hp83 is a BC857 GP PNP from Philips. Looks better now. (...) I think photo diode used in photovoltaic mode. It looks like it pushes the voltage down from that established by (...) (25 years ago, 3-May-99, to lugnet.robotics)
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