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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1k views

How to control switch mode power supply feedback voltage through optocoupler?

The larger design is for a 170 V input, 500 V 2 mA output using a flyback converter. I will refer to the schematic on page 29 of the LT3751 switching controller, also found below. The feedback pin of ...
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62 views

isolating between two power

for better isolation and because of sparking at the contacts, it is suggested using a separate supply with optoisolation like an image attached, but in my design, I wave only one power supply and I ...
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191 views

Calculating Component Values for MIDI synth

I am reasonably new to this, and I am trying to find the calculations used to choose the component values in this circuit. Concerning the Optocoupler, from what I can work out: 6N139 Forward ...
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1answer
150 views

How can I multiplex fully isolated differential signals?

The issue quickly explained I would like to switch between two fully opto-isolated Tx differential signals (RS422). How can I achieve that if the grounds are different for the signals and the analog ...
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1answer
467 views

Is the ground necessary with an opto-isolated RS422 signal

I have 8 opto-isolated RS422 ports to install. All of them are coming from a single PC card. It provides the opto-isolation for every RS422 port. Every signal is opto-isolated from the PC ground and ...
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55 views

Triac doesn't triggering when the power jack pins switched?

I built a power circuit with MOC3063 & BTA40600 for controlling heating element (2000 watts) according to the image. when I plug the jack in let's say one direction the circuit works like a charm ....
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1answer
593 views

SWD optoisolation problem

I have designed the following optoisolator for SWD interfacing with an STM32 device and J-LINK programmer: This is the generic schematic: And this is a single optoisolator schematic: I am not able ...
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2answers
297 views

PNP transistor with audio signal output on collector is used to drive opto-isolator. How does it work?

I have tried assembling the circuit but it doesn't work. Now I need to understand how it works in order to debug it. The part that confuses me is: Channel 1 is a standard audio output from a ...
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94 views

Switching circuit and reducing noise

Need your opinion in a design I'm working on. Please see circuit below. So I need to control the mcu GPIO based on the incoming 24V signal. The signal is attached below. My issue is this 2 times out ...
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1answer
151 views

Is the isolation necessary in this circuit?

I am designing a circuit to control LED drivers. The main characteristics are the following: The circuit is powered through the electrical network (230 VAC) It has three types of dimming outputs: 0-...
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568 views

DALI Click Board: Not clear about the board operation, usage and circuit design

I am developing a DALI Control Device using STM32 board. I have already programmed the board to send DALI Slave commands according to DALI Protocol. But I am facing problem interfacing my board with ...
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1answer
107 views

calculating transistor base resistance in parallel circuit

I am trying to use Raspberry Pi GPIOs to turn on and off optocouple switches controlled by transistors. I really have no idea what I am doing (programming the thing okay. Wiring it? Not so much). I ...
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210 views

How did I break this optocoupler?

I'm trying to use an H11AA1 (datasheet) optocoupler to test when my doorbell is pressed (I'm in an apartment building): simulate this circuit – Schematic created using CircuitLab It worked ...
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195 views

Triac randomly triggers when there is noise in the supply [duplicate]

I am using BTA16-800CW (Snubberless version) to control AC appliances (LED lights) and it randomly turns on / flickers when I adjust the fan regulator in the same room (this may be creating some ...
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2answers
347 views

24v Emergency Stop Input

What's a good way to read a 24v emergency stop signal with an mbed? The 24v signal is connected to an E-stop contactor which disconnects power to a motor when the 24v is interrupted (i.e. when e-stop ...
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2answers
2k views

H-Bridge design understanding

I have been set the task of creating an h-bridge that can control a 12V DC Drill motor. Below is a slightly modified version of the document I have been given to help me get started: I don't ...
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1answer
154 views

Trying to debug a PWM motor drive with cascode configuration - is the MOSFET busted?

I made a simple DC/universal motor drive as per the circuit in the picture. I was experimenting with it by powering it from a variable transformer. Note that both Vdd (300V) and the 12V Vb1 (for ...
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3answers
200 views

what happen if a high voltage connects to pc-based oscilloscope's ground?

What happens if a high voltage (for example 500V) is connected to PC-based oscilloscope's ground? In principle, nothing should happen, but if somehow the PC's ground and high voltage's reference tied ...
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1answer
369 views

Designer circuit using optocoupler

I have a raspberry pi trying to drive an intercom system. The intercom has a 12V output which when connected to ground opens the door. What I want to do is have the raspberry pi 3V GPIO switch ...
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1answer
172 views

Diode in 6N138 optocoupler

I'm currently in the process of getting MIDI input to my Raspberry PI through UART, and in order to follow the standards, I should optically insulate the MIDI cable from the RPI by using an ...
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1answer
3k views

how to calculate resistor value for optocoupler - 230V [duplicate]

I am trying to implement the following circuit. I am trying to understand how the resistance values are calculated. I followed this - "how do I calculate resistor value" According to my optocoupler (...
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1answer
533 views

How to drive optoisolator from Mains

Most of the circuits that I have seen, MOC3021 or similar opto-isolator is driven from Micro-controller. I want to do the opposite - Can I drive the opto-isolator from mains supply and use the other ...
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1answer
717 views

4N25 optocoupler drive solenoid [closed]

I am trying to drive solenoid using above circuit but its not working with IRF540 mosfet. Can anyone help me the what is wrong with above circuit. Thanks,
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3answers
405 views

PC817 voltage floating [closed]

I'm using a optical coupler (pc817) to transmission my Digital signal,i can measure stable voltage on pin 1 , But I do not understand why the voltage on pin 2 is floating ,and it will cause my output ...
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1answer
212 views

Why use triac when opto-coupler can already handle mains voltage

I have recently seen a opto-isloated triac driver circuit. The Gate terminal of triac is connected to a live wire through physical switch. So when the physical switch is turned on, triac conducts and ...
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1answer
458 views

DALI schematic: help to analize reception circuit and limited current supply

I am trying to understand how this schematic works. It is a physical layer implementation of the DALI specification. The schematic is in this document (page 11). I have mainly two questions: In ...
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1answer
560 views

DALI specification: help to understand the physical layer schematic

I am trying to understand an NXP circuit that has implemented the physical layer of the DALI specification. In particular, it is DALI master hardware. For the transmission (page 4), it says exactly: ...
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1answer
860 views

How to trigger a “Relay Module With OPTO Isolation Support High or Low Level Trigger” with a momentary switch

I am a complete novice with anything beyond simple wiring of guitar effects and kits. I have a unit, a Roland GR-55, that has a momentary switch built-in. I want to trigger this switch with a separate ...
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3answers
117 views

Is the rise time of the output of a logic IC or optocoupler independent of the rise time of the input?

Is the rise time of the output of a logic IC (e.g. flip-flop or inverter) or optocoupler independent or dependent on the rise time of the input? If the answer is dependent, are there any other ...
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2answers
607 views

Speeding up turn-on and off with VOM1271 Photovoltaic MOSFET Driver (/optocoupler)

It's my first post here so please do not hesitate to tell me if I'm not doing it right :-) A bit of context : we need to switch an array of power resistors (1,3kW, 1ohms) in order to test under load ...
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2answers
2k views

Triac not getting switched by optoisolator

I made this dimmer circuit: simulate this circuit – Schematic created using CircuitLab And it does not work (no light). I have looked up other circuits that serve the same purpose and they ...
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1answer
183 views

Wide range current sensing at +5kVDC

I am working on a control and interface board for high voltage supplies, which requires some current measurement to be implemented. The general terms of the question are similar to this one. The ...
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1answer
57 views

Opto Triac temperature shut off

I am using a opto triac rated at 100C operational. It controls an externa SCR in a very common fashion. The opto Is physically located next to a heat source component making the opto temperature rise ...
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4answers
406 views

Optocoupled MOSFET drive

I have a high power 12V rail that I would like to keep separate from the logic supply, and so would like to optocouple the N-MOSFET drive for an external high power LED light. Does this seem like a ...
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1answer
95 views

Do phototriac optoisolators (e.g. MOC3021) require pulse trains?

I have a project where I need to make a microcontroller trigger an old, non-controlled, camera flash (think of discharging a capacitor through a xenon lamp). First idea was use a transistor-based ...
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0answers
131 views

Using NPN transistors as switches for low-current, 3VDC infrared transmitter device

I'm currently trying to hack up an IR remote for electric holiday candles so that I can use Amazon Alexa or Google Home to turn them on or off. To do so, I need to trigger the switches on the hand-...
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304 views

Can triac opto-coupler used as a simple optocoupler?

I had more than 50 pcs of MO3041 but in my circuit need operation like 817. I know i can use 817 for DC circuit but i am just want to know if i can use MO3041 in DC circuit. I know there is a simple ...
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1answer
132 views

Driving a DC motor in two directions with an opto-isolator

i need yo realize a circuit using an opto-isolator to drive a dc motor in 2 directions i've found this: Driving a DC motor (in one direction) with a microcontroller pin and an opto-isolator but it is ...
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1answer
103 views

Programmatic On / Off Control of 3.3v board power

I'm running some tests on a board I have developed. As part of these tests I would like to run a command, then quickly (like microsecond or less time) cut the power from the board. To perform these ...
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1answer
62 views

Reproduce 2CH Relay Optoisolated on custom PCB

I'm designing a custom PCB that implements a relay section. I would "reproduce" the schematic of the 2 Channel Relay optoisolated so common in hobbystic. The selling shield is And the schematic is: ...
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1answer
179 views

Problem with using SCR to control power for an electric grill

I'm doing a power controller for an electric grill, where through PWM I allow to pass x number of cycles from the 124V @ 60 Hz source of my lab. Here you have the diagram: simulate this circuit &...
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1answer
195 views

Automotive Arduino

I was designing a circuit to manipulate in's and out's in a car. I use a step down converter to power up the Arduino. The inputs, in the left of the Arduino are: GIN : General grounded Input. ...
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1answer
938 views

optocoupler H22A2 driving a plc input

https://www.vishay.com/docs/83741/83741.pdf example 2 I have existing H22A2 optocouplers that I am trying to run 12vdc through to get a plc input to turn on and off. I am using a 1k resistor on the ...
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1answer
79 views

Use 2 optocouplers?

What is the advantage of using two feedback optocouplers? I'm not sure why this single voltage power supply would use 2.
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1answer
162 views

PWM circuit explanation [closed]

I have the following circuit that I am using to implement an Arduino project. Now I tend to focus more on the coding side of things usually so I lack the electrical knowledge. Could someone please ...
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4answers
489 views

Comparator output not fully switching on MOSFET

First Question for me. I have benefited from other answers here but have not fully resolved my problem. Here's my problem... The LM311 Comparator output does not drive the N channel MOSFET fully on....
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1answer
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Modify PWM controlled 230v incandescent bulb dimmer circuit

I have a PWM output from one device (Arduino) and want to use that output to dim an incandescent 230V 60W light bulb. I found this circuit online which does what I want it to do. From the way I ...
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0answers
152 views

Swap main terminals of zero-crossing triac

The question I have is maybe silly, but I cannot find strictly related info. When designing a mains switch with an optotriac driven triac (or discrete SSR for you), during layout I swapped the ...
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3answers
2k views

6N137 Optocoupler Pin Configuration

I am not an engineer. I have researched basic information that can be found on optocouplers. I understand the theory of 4 pin optocouplers. I believe I even understand basics of 6 pin optocouplers. ...
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4answers
4k views

Why use an opto-coupler?

A side note: please be forgiving of me because I'm just starting out in Electronics so I'm still confused about certain terms. Why are optocouplers used? Yes I know they link a circuit together ...