Author Topic: How to connect Linear Analog Optocoupler  (Read 1374 times)

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Offline ajoseph88

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How to connect Linear Analog Optocoupler
« on: September 25, 2015, 01:50:10 pm »
I am using Analog optocoupler HCNR201, to isolate the dc armature voltage from the motor and use it as a feedback.
So i am having two confusions,
1. I did not understand the pin diagram, and how to connect... data sheet is confusing for me...
2. Datasheet says Vf peak is 1.95 volts, so what is that... and how to connect my input of 0 to 5V to get the same output of 0 to 5V with isolation, as there seems to be 6 pins and I suppose i should use a buffer op-amp as well...
My god, I am dumb as a donkey... I am one of the dumbest persons in the world trying to learn electronics... Shit...
« Last Edit: September 25, 2015, 01:52:21 pm by ajoseph88 »

Offline macboy

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Re: How to connect Linear Analog Optocoupler
« Reply #1 on: September 25, 2015, 04:36:20 pm »
Why do you need isolation between the controller and the motor it is controlling?
Describe your setup in as much detail as possible.

Offline alsetalokin4017

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Re: How to connect Linear Analog Optocoupler
« Reply #2 on: September 25, 2015, 06:03:50 pm »
The datasheet I  looked at gives several application circuits, using op-amps, that would appear to fit your application, if I am understanding your needs correctly.

This optocoupler has one LED light source inside it, which is driven by the input signal, and two separate phototransistors which are actuated by the light from the internal LED. The "1.95 Vf peak" refers to the forward voltage of the LED, it's just like the Vf figure for any LED or diode. The pinout seems straightforward to me, with two pins for the LED ( one anode and one cathode), and two pins each for the phototransistors (emitters and collectors). (The light from the LED acts as the "base" signal for the PTs.)
The easiest person to fool is yourself. -- Richard Feynman

Offline TimFox

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Re: How to connect Linear Analog Optocoupler
« Reply #3 on: September 25, 2015, 06:11:37 pm »
In an ideal optocoupler, the collector current of the phototransistor is proportional to the LED forward current.
In the next approximation, the base current is proportional to the LED current, and the collector current is approximately proportional to that base current (hFE is not truly constant).
Of course, all of these currents are unipolar (no polarity reversal).
If the two transistors are well-matched, one can give feedback to the LED driver and the second one, galvanically isolated from the first, can deliver current to its load that is well-controlled, being equal to the current in the feedback transistor.

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