Author Topic: photodiode vs LDR in line follower  (Read 14135 times)

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Offline Soeren

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Re: photodiode vs LDR in line follower
« Reply #30 on: April 21, 2009, 04:00:53 PM »

today im just checking with another groups members that using phototransistor with IR led in their project. I try to use white paper facing on the IR LED and its was reflected to the phototransistor. But photodiode cant. ???
A phototransistor is more sensitive (but much slower - not something that will affect your use of it though) than a photodiode. You can view a phototransistor (sensitivity-wise) as a diode followed by a transistor, so the sensitivity is greater by a factor of the transistors h_FE (current gain).
The op-amp circuit can be made to reflect the IR with a piece of paper, even with a photodiode... But not until you actually get your hands off the keyboard and on your circuit :)

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives


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