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Questions tagged [opto-isolator]

An optoelectronic device which combines an optical transmitter and receiver in a single package; commonly used in galvanic-isolated control applications such as power supplies.

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Zero Crossing Signal Timing

I have a zero crossing circuit for dimming lamps exactly like the below According to my calculations: \$ I_{R7} = \frac {V}{R} = \frac {3.3}{10k} = 0.33~mA\$. Considering TCMT1109 transfer ratio ...
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1answer
67 views

Random values of voltage near ADC in current loop

I have implemented a circuit which allows to isolate a current-loop-based sensors. The schematic is as follows: Everything seemed to work good in the breadboard. Without a MAX14626 IC, the circuit ...
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1answer
38 views

BT136 TRIAC not closing on LOW signal to the MOC3021

I am trying to make an AC dimmer. I am following this schematics for my circuit, Circuit Link as you can see in the below picture that I am able to turn the signal on after a short while of zero ...
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2answers
106 views

Building a midi project with Arduino + scrap components (optocoupler and diode)

Original title: 300V output Optocoupler in a 5V circuit I'm (new to this) trying to build a midi controller (in and out) with arduino and scrap. I guess I had several questions in one so I changed ...
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103 views

Optocoupler Characteristics

In my application I need to isolate a PWM signal @ 1 kHz, which is generated from a Beaglebone Black microcontroller. In my signal, I want to have one hundred different steps in duty cycle (from 1% to ...
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1answer
41 views

Calculating resistors for an optocoupler controlling a pmos

I want to use a pmos (SI7157DP-T1-GE3, datasheet) as switch - controlled by an optocoupler (TLP291(V4GBTP,SE, datasheet) which is controlled by a teensy 3.6 (3V3 output voltage). Now I'm calculating ...
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70 views

Why use opto-isolation in this way?

I'm synchronizing two FLIR cameras and FLIR's use of opto-isolation in this document doesn't make sense to me. Could someone explain the benefits of using opto-couplers as FLIR describes? The two ...
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88 views

Are activated open-collector and open-drain circuits wasting energy?

Consider the following reference circuit for a 6N137 optocoupler. My understanding is that this circuit uses a pull-up resistor on the output node so when the optocoupler led is activated, the ...
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111 views

Can an optocoupler be used as a switch [closed]

I am trying to replace a analog switch (the switch is a momentary button in a low current DC situation) with optocoupler. Is it possible to use an optocoupler as a switch (i.e. just on/off)? ...
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1answer
62 views

zero-crossing detection: to optocouple or not to optocouple?

That is the question. Most of the diagrams I have seen on the interwebs are of the opto-coupling school of thought: But the AVR182: Zero Cross Detector application note just throws in the resistors ...
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1answer
75 views

What's the difference between these varieties of octocoupler? [duplicate]

It looks like ON Semi makes a bunch of different kinds of optocouplers for various applications. The array of choices is kind of bewildering. What, exactly, is the difference between an optocoupler ...
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57 views

What is the difference between optoisolator and motor driver?

Suppose we need to control power of a device (12v, 500mA). I tried to use TLP281 board, which works, except that it inverts the output: device is powered when there is no control signal. For this ...
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51 views

Best way to shift automotive logic to Arduino TTL

My vehicle ignition switch voltage is 9V when the vehicle is not running. It is 6V when button is pressed. I need a way to convert this to TTL Arduino digital logic levels. I thought I could use a ...
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1answer
95 views

how does single supply op-amp work while its non-inverting input is connected to ground?

In HCNR200 Datasheet, the page 11, figure 13-A, there is a sample that confused me. In this sample, the Vin is applied to the inverting input and if the electric current passes through PD1, PD1 ...
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41 views

P-channel FET and CNY17-3 opto isolator

Long story short, I want to have a relay turn OFF when the output of a 4017 goes high. So I installed an opto-isolator, connecting the LED to the output of the 4017, ie "on" until the ouput goes high....
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48 views

Simplifying this circuit using optotriacs?

I'm currently trying to create an interface between my Arduino-compatible (NodeMCU) and my OpenTherm boiler. OpenTherm is a protocol used by some boilers (mainly in Europe) which allows for the ...
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1answer
54 views

Optocoupler 5V to STM32F407 3.3V

I have to connect 8 optocouplers as shown in the picture with STM32F407 MCU. These are giving 8 digital signals to the MCU. The supply voltage at the outputs of optocouplers is 5V DC while the ...
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1answer
101 views

Optocoupler is failing to isolate circuit

I have a circuit in which I am trying to use an microcontroller to activate a car horn. I've had a lot of trouble trying to isolate the horn from the rest of the circuit. I have the microcontroller ...
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2answers
124 views

What is the purpose of these diodes in this opto isolator circuit?

I came across this circuit which I think is to isolate a high voltage signal to a safe level for GPIO of a 3.3V micro controller. My question is that how on earth this circuit works...There are 2 ...
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2answers
54 views

what limits the maximum voltage of this optocoupler (6N137)?

In the datasheet it is stated that the maximum VCC voltage is +5.5V.(https://www.vishay.com/docs/84732/6n137.pdf) Because ive been told to question everything (and i have enought of them to kill one ...
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1answer
61 views

Help for voltage is being passed trough load, even triac is OFF condition

We are using below circuit for home automation. We are facing problem when 5v battery is not passing to the circuit,but even 1 volt is being passed trough load, even triac is OFF condition.. Please ...
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88 views

Triac BT 136 getting shorted when load is given to T1

We have a optocoupler switching circuit which triggers the TRIAC with ZCD. Everything is working fine with all inputs. Connection is T2 as a input T1 as output Gate as Trigger from Optocoupler As ...
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56 views

Acquire a “TIC” signal from a power meter

I'm trying to acquire the tic signal of a french power meter. From the datasheet available here of the TIC signal we can find out that the signal is (page 7/38): 6 Vrms +/- 10% at 50 kHz It comes ...
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0answers
83 views

Optocoupler 24V input misbehaving

I have an optocoupler circuit that is used to accept 24V input (100 ms pulses) and interfaced to a microcontroller. The schematic is as follows: Opto: BL817C or TLP621. TLP621 datasheet As per my ...
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3answers
54 views

Can you and/or why should you not replace optocouplers with transistors when dealing with slightly different voltage

I stumbled upon this: https://gyazo.com/9f495ed8e9005ab440db8061839f412a so the mdb bus is communicating at a 34v level and the other side is at 5 or 3.3v why are they coupled with a optocouplers ...
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2answers
102 views

How isolation is achieved in isolated channel oscilloscopes?

I tried to search something about this but found only a small amount of information. What confuses me is that all isolation amplifiers, optocouplers etc. I could find usually work at much lower ...
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1answer
63 views

GPIO connected as open-drain to opto-isolator's cathode

When connecting GPIO output pins (RPi, uC, ...) to an opto-isolator, the classical way I know is the following (at least I understand that it can roughly be depicted like that): simulate this circuit ...
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1answer
69 views

Voltage sampling from 220vac to 5vdc

I made a 1 phase to 3 phase inverter using arduino and IR2104 to control the speed of an induction motor and it is working perfectly. To complete the protection scheme, I need to monitor voltage of ...
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2answers
72 views

Help understanding power ratings in optocoupler datasheet

I want to understand this the datasheet for the Everlight EL817 optocoupler but don't know what is the maximum power can the output hold. I see an optocoupler as a kind of switch that closes a ...
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1answer
62 views

How much current does this Opto isolator output (HCPL-3180)?

I wanted to use it like this in this configuration][How much current does this Opto isolator output (HCPL-3180) ?
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3answers
63 views

optocoupler - Does the current limiting resistor of the led make a difference

Does the led current limiting resistor for the led make a difference to the performance/behaviour of the optocoupler? Is it just like how a normal transistor would work, if you drive the base harder,...
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42 views

Opto-coupler and switching digital pins

I'm a total noob when it comes to the use of opto-couplers, but I'm trying to connect up a couple of digital pins between an ESP32 and a small voice module. There are two pins that I need to switch ...
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2answers
42 views

Interpreting some functions of an optoisolator from its datasheet

I cannot interpret couple of things from the datasheet of this optoisolator. 1-) Is there and hint in the datasheet regarding the maximum CM voltage interference it can handle at its inputs? 2-) The ...
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50 views

LED and optocoupler MOSFET switch connected with an inductive load

I want to ask, if this circuit will work. I think the flyback from the inductive load the mosfet is connected to will break the optocoupler. The LED is connected through a resistor which should ...
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34 views

Opto-coupler to convert current into voltage

I am using TPS26601 for my next design. There is a pin IMON which outputs current proportional to current flowing throwing the output pin. The gain ranges from 72 ...
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50 views

Sizing the input current of a isolated standalone MOSFET gate driver for a stable output

After a suggestion from my previous question I'm planning to use this Photovoltaic isolated MOSFET gate driver to trigger a trigger input of this DAQ. It seems these devices do not require an ...
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1answer
46 views

Optoisolator Not Switching

I’m working on a university project that involves switching a relay using an ILD213T optoisolator. The optoisolator is driven directly by an ATmega328p. I had calculated the required current limiting ...
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1answer
76 views

Using Opto-Coupler with STM32

My question might be already answered but I have some problem with resolving it. I'm using PC817 Opto-Coupler to turn on a relay. My VCC voltage is about 4.2 volts and the MCU is an STM32F4 with 3.3v ...
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1answer
72 views

MOC3021 optocoupler not working ( or not working , a bit confused )

My Understanding As far as my understanding of MOC3021 optocoupler goes, it should latch pins 4 and 6 whenever there's a current flow between pins 1 and 3. The Confusion Image 1 - D1 not glowing ...
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1answer
50 views

Opto-Isolater always on by higher voltage

I use an AQH3213 Opto-Isolater. When I use 3.3V on the 'dc motor side', everything works fine and it 'turns off and on in an interval of 1 second'. But when I use 5V, it's always on.... Do you have ...
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1answer
91 views

Noninverting optocoupler with a pulldown resistor

I am using a power MOSFET to switch a solenoid valve. The MOSFET is driven with a optocoupler (LTV-847) to isolate the 12V required to switch the valve from the 3.3V used by the microcontroller. ...
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1answer
126 views

microcontroller is “hanging” when it is feeding PWM to a DC motor controller

I am using linear potentiometer to control the speed of a DC motor. I am using the following schematic. An ATmega328P receives the value from linear potentiometer via analog read. This ATmega328P ...
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2answers
105 views

How series resistors influence clearance-creepage requirements?

simulate this circuit – Schematic created using CircuitLab I'm designing a circuit which should leak some amount of current from AC line to PE. The question is regarding clearance-creepage ...
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3answers
1k views

No current through AC optocoupler

I am just testing this component MOC3021 optoisolator, its datasheet can be found here. This is my circuit in Proteus: Please forgive me for my ignorance of electronics, I have my background in ...
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37 views

phoresistor vactrol tremolo noise

I made an optocoupler by shrink tubing a generic photo resistor and a cold white led. Then used it in the following setup to be able to control audio level to achieve tremolo effect: simulate this ...
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32 views

Circuit to a/b switch like a relay would. So an analog or digital signal can be turned on or off or routed

I need to build an arduino-based switcher / router for a multi-arcade to route controls to different game boards, and also switch 2 vga inputs into one output. Without introducing any lag also. 3 ...
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2answers
146 views

Using optocouplers at the end of a twisted pair

I am designing a dumb "isolation box" that is to sit between a computer and medical data acquisition equipment. The purpose of this box is to inject power and to provide communications and digital ...
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2answers
73 views

What is optocoupler and how it is used? [closed]

Im curious about optocoupler. What is optocoupler,why and how it is used in electronic circuits ?
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1answer
63 views

What does “off-state output terminal voltage” in optocouplers mean?

I was looking at possible options of what optocouplers to use in my project. I was looking at these parts. https://www.fairchildsemi.com/search/?searchText=MOC3023-M#N=&&Nao=0&&Ntk=...
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1answer
52 views

Achieve -12~12V PWM Signal isolate

I have used IL300 to isolate 0~5V PWM signal before and it works great. The circuit is shown below. But now I need to isolate -12 ~ +12V PWM signal. Is there any possibility or suggested circuit to ...