Electronics > Beginners
Could you help me understand this optical encoder Datasheet?
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Blitzschnitzel:
So, I want to order this quite pricy optical encoder:
https://static6.arrow.com/aropdfconversion/b37bee95f5eae7e7f00cc37d7f45757e265dbb6b/50924574275363em14.pdf

If I understand it correctly there is an IR LED inside and two Photodiodes. When light passes through the slotted wheel, the diode becomes conductive.
What I don’t understand is where the Diode connects to. VCC or ground? The schematic in the Datasheet just shows an unhelpful box. On the first page it says output voltage 4v. Does that mean the signal pins either float or forward VCC minus a bit?
ataradov:
There is internal circuit that creates a voltage output. The voltage will be 0-0.8V indicating logical low and 4.0-5V indicating logical high.
ledtester:

--- Quote ---When light passes through the slotted wheel, the diode becomes conductive.

--- End quote ---
It is more likely that phototransistors are being used for the two channels:

https://www.rohm.com/electronics-basics/photointerrupters/what-is-a-photointerrupter

Without a pull-up resistor the output of a channel would be either 0V or floating. Since the datasheet describes the output as either LO or HIGH and doesn't show that pull-up resistors are needed my guess is the device has its own pull-ups.

Blitzschnitzel:
Ah, Thank you very much! I want to connect the encoder to an atmega 32U4 And the IO pins state low up to 0.9v. That’s very close to the 0.8v. Should I put two resistors in series with the signal pins to reduce the voltage a bit? I am not sure about the value though if I want to reduce by, let's say, 0.5v because there is supply current and output current. Does supply current already include output current?
ledtester:
The datasheet says the 800 mV LOW signal is a maximum, so I wouldn't worry about it. In practice I would expect the LOW voltage to be a lot lower than that.
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