Robotics : 14811


Robotics / 14811	14810 \| 14812

Subject:	Re: Shutting off illumination LED on Light Sensor for LIDAR
Newsgroups:	lugnet.robotics
Date:	Sat, 31 Mar 2001 06:35:03 GMT
Viewed:	820 times

> Someone else mentioned that LegOS is able to read the light > sensor 'passively' without illuminating the LED. Any LegOS > folks here know what they do differently? I strongly suspect this is a myth. A transistor is a transistor is a transistor. They all require biasing in order to function properly and that requires power. Mind you, even so-called passive devices must either generate a voltage or have a voltage present in order to read their value, and it's probably that reduced voltage that is in fact powering the light sensors. Not a high enough voltage to light the LED (min 1.2V - more likely 1.9V - I haven't tried it yet) but enough to get the photo-transistor biased (but not properly), Hence a weak and non-linear reading. Matthias Jetleb VA3-MWJ

Message has 1 Reply:

		Re: Shutting off illumination LED on Light Sensor for LIDAR
(...) Actually you don't need LegOS, any input set to raw mode with the LEGO firmware will do fine. This is because even in passive mode there is a pull up of 10k to 5V, and in fact the LED is glowing dimly in this mode. Just tried it, I can get raw (...) (24 years ago, 1-Apr-01, to lugnet.robotics)

Message is in Reply To:

		Re: Shutting off illumination LED on Light Sensor for LIDAR
(...) Thanks for all the tips, everybody. I set out last night to open up my light sensor and add a jumper to allow me to take the LED out of the circuit. I was unsuccessful in getting the casing open, even after cutting the underside latching tabs (...) (24 years ago, 29-Mar-01, to lugnet.robotics)

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