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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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How make a pulse acquisition from an electrical meter directly into a raspberry pi?

I would like to acquire pulse informations from a french electrical meter. There is a picture of the outputs of this electrical meter. These pulses vary in frequency and after acquisition, we can ...
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4answers
39 views

Normalised Current Transfer Ratio of Opto-Coupler

My understanding is that the Current Transfer Ratio of an opto-coupler defines the relationship between the current flowing through the LED, and the maximum supply current of the output. e.g. "5ma ...
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2answers
37 views

24V signal switching optccoupler

We have a robot, and it has 32 digital output, fed into a homemade PCB. On the PCB we have optocouplers, which have a forward voltage around 1.2-1.3V. So I need to drop the voltage a lot. That's why ...
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34 views

Problem with ground loop in audio system? USB and minijack at the same time [closed]

My hardware setup is: PC with external USB audio card + smartphone. Smartphone is connected via USB to PC and via minijack to USB audio card at the same time. Problem doesn't appear when I disconnect ...
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59 views

Driving of a MOSFET using optocoupler in 180-to-24V buck converter

i have a problem with driving a MOSFET in a converter, let me explain. I need to build a Buck Converter with the following requirements: Input 180 V (From a 120 VRMS rectifier circuit) Output 24 V No ...
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2answers
64 views

Triac Switching circuit with Optocoupler

I am trying to control home devices using a microcontroller and a TRIAC. For switching, I intend to use an optocoupler and triac-based circuit. The circuit is given below (also plenty are available on ...
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1answer
49 views

TL431A issue in voltage [closed]

I am using TL431A for my design. Input side 4.7V below emitter and collector should be short and above 4.7V no output. But in my design it's the opposite. Can anyone suggest how to attain ex cat ...
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70 views

Wide Range Input (Sinking/Sourcing) to Arduino

Figure 1: I am trying to create a circuit that will take a 24 to 3 v digital signal that I can connect to an arduino input. I'd like to have an indicator in the circuit to show that the signal is ...
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1answer
953 views

Do I really need diodes to receive MIDI?

All the schematics above use a diode before the receiving pin on the optocouplers. The problem was, I never able to find the exact same diode as the schematics. Before, I'm using H11L1, but it never ...
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2answers
61 views

Optocoupler isolation necessary?

The circuit diagram below shows two possible options for a circuit: simulate this circuit – Schematic created using CircuitLab The difference between both circuits is the use of the ...
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2answers
46 views

HCPL3700 - 220V sensing circuit

I want to use HCPL3700 optocoupler for sensing 220V (line). I design a circuit but I want to ask some questions. HCPL3700 is an open-collector output so I pull-up Vout. In AC voltage sensing some ...
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3answers
68 views

Replace some LEDs with diodes in relay circuit

I need to know if I can replace the input LEDs (IN1, IN2, IN3, IN4) by a diode or resistor and if this can help me to reduce the voltage consumption generated by these LEDs. The circuit is a 4 relay ...
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1answer
42 views

Resistor value for Opto-coupler input

This question is in regards to the EL817 Opto-coupler(http://www.everlight.com/file/ProductFile/EL817.pdf). I'm trying to choose a suitable resistor to lower the current/resistor of the Opto's LED. ...
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1answer
36 views

Reverse function optocoupler in series with physical NC switch?

I've read this answer (reverse function optocoupler) but my case is different: I've got a CNC mini lathe. I have a limit switch on one of the lathe's axis ends (X+) wired as NC to my Gecko G540 ...
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1answer
32 views

Optoisolated MOSFET to control a load - should I take in consideration MOSFET typical use?

I've already asked a specific question, but I'd like to evolve it in a more general question. In a typical optoisolated IC like this: Should I or not interconnect control (-) and DC (-) or will I ...
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2answers
82 views

Zero crossing detector inconsistency

I designed the following zero crossing detector using an FOD819S optocoupler (U5): The source of the optocoupler is connected to a MB6F full-bridge rectifier (D2) which is supplied by a 9V ...
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2answers
41 views

How to connect power phototriac's gate pin?

I have inherited a design that uses a power phototriac (basically an optotriac with a built-in TRIAC) -- the VO2223B -- that includes a pin to access the power TRIAC's gate (pin 5 below). The ...
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1answer
35 views

Pulldown on optocoupler's input side

I saw some schematic that uses optocoupler to make isolation to the MCU digital input pin. Schematic below. I was wondering why do they need R700 as a pulldown since the LED inside the optocoupler is ...
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1answer
42 views

Using LEDs in series with optocoupler for biosensor

Long time lurker, first time asker. I've been working through a biosensor schematic from a BME class to build an EKG (I'm a physician, aware of risks of these devices etc) (typical voltages being ...
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4answers
271 views

Why is this 100k resistor placed in this circuit?

I got a status taken circuit (as shown) from Google .. My doubt is why this 100k is placed in neutral line? any other way can modify the input ? By appling 230v AC directly effect the ...
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4answers
3k views

Interfacing a button to a microcontroller (and PC) with a 50 m long cable

I am designing a board that will be plugged into a computer and will read the status of a button ~50 m away in an office environment (it's actually a lot closer, but the cable is long). I think ...
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1answer
37 views

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
76 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
69 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
144 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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6answers
112 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
53 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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0answers
75 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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3answers
91 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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4answers
124 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
70 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
78 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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1answer
61 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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1answer
60 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
96 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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54 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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0answers
54 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
70 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
102 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
137 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
71 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
66 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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1answer
114 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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59 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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124 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
60 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
105 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
83 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
70 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
92 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 ...