Author Topic: Could you help me understand this optical encoder Datasheet?  (Read 837 times)

0 Members and 1 Guest are viewing this topic.

Offline BlitzschnitzelTopic starter

  • Regular Contributor
  • *
  • Posts: 64
  • Country: de
Could you help me understand this optical encoder Datasheet?
« on: September 19, 2019, 09:54:23 pm »
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?
« Last Edit: September 19, 2019, 09:56:15 pm by Blitzschnitzel »
 

Online ataradov

  • Super Contributor
  • ***
  • Posts: 11905
  • Country: us
    • Personal site
Re: Could you help me understand this optical encoder Datasheet?
« Reply #1 on: September 19, 2019, 10:10:59 pm »
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.
Alex
 

Online ledtester

  • Super Contributor
  • ***
  • Posts: 3283
  • Country: us
Re: Could you help me understand this optical encoder Datasheet?
« Reply #2 on: September 19, 2019, 10:47:36 pm »
Quote
When light passes through the slotted wheel, the diode becomes conductive.
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.

 

Offline BlitzschnitzelTopic starter

  • Regular Contributor
  • *
  • Posts: 64
  • Country: de
Re: Could you help me understand this optical encoder Datasheet?
« Reply #3 on: September 19, 2019, 11:33:18 pm »
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?
 

Online ledtester

  • Super Contributor
  • ***
  • Posts: 3283
  • Country: us
Re: Could you help me understand this optical encoder Datasheet?
« Reply #4 on: September 19, 2019, 11:42:25 pm »
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.
 

Online ataradov

  • Super Contributor
  • ***
  • Posts: 11905
  • Country: us
    • Personal site
Re: Could you help me understand this optical encoder Datasheet?
« Reply #5 on: September 19, 2019, 11:42:40 pm »
No, don't worry about it, just connect it directly to Arduino and you will be fine.
Alex
 

Online ledtester

  • Super Contributor
  • ***
  • Posts: 3283
  • Country: us
Re: Could you help me understand this optical encoder Datasheet?
« Reply #6 on: September 19, 2019, 11:46:12 pm »
No, don't worry about it, just connect it directly to Arduino and you will be fine.

Yes - after all the datasheet states: "HCMOS, CMOS and TTL compatible" so no special interfacing is necessary.
 

Offline BlitzschnitzelTopic starter

  • Regular Contributor
  • *
  • Posts: 64
  • Country: de
Re: Could you help me understand this optical encoder Datasheet?
« Reply #7 on: September 19, 2019, 11:53:25 pm »
OK. Thank you very much. :D
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf