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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1answer
150 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 ...
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45 views

TRIAC confusion

First for some quick background: You might be aware of my other threads in which I pose a problem with micro-controller to WiFi-command an existing coffee machine which had (as happens with a lot of ...
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2answers
182 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
83 views

How do I make an io pin 12v tolerant?

I've seen plenty of 3v3 circuits that are 5v tolerant, but I'm wondering if I can make something that is 12v tolerant. Basically I have a numato 128 gpio expander and there are so many wires that one ...
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1answer
88 views

Detect 10V…To.. 260V AC/DC with HCPL-3700

I want to detect voltage between 10V and 260V AC / DC, I have thought to use the HCPL-3700 but if I put the 47k resistors the output is activated, but if I apply 12V the output is not activated. Does ...
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voltage level handled using optocoupler [duplicate]

I want to program at89c2051 chip. I am referring circuit diagram where the optocoupler is used to handle the 2 voltage levels (+12V and +5V). i didn't understand how Pin A0 and A1 will control the ...
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1answer
352 views

Driving a DC motor (in one direction) with a microcontroller pin and an opto-isolator

I'm supposed to design a circuit for driving a DC motor with an opto-isolator and a microcontroller pin. The motor is supplied with 12V, and its power is 5W. The opto-isolator has to isolate the ...
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1answer
32 views

Circuit design for triggering multiple optocouplers at constant voltage level

I have theoretical understanding of general electronics basics, however I do not have any practical experience in circuit design. Therefore I need some advice of what would be the best practice on how ...
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3answers
127 views

Looking for a medium power optocoupler

I have a project where I will control a 3 or 6 watt UV lamp DC with a microcontroller. I want to power my lamps with a AC/DC circuit and switch them on and off with a optocoupler, mainly because ...
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38 views

Reading Optocouplers datasheet: current transfer ratio (CTR)

So I am working with an optocoupler at the moment, and having trouble understanding what CTR value to use in my calculations. The datasheet states 50% Min and 600% Max, which is a huge difference. Do ...
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1answer
42 views

Voltage divider on optocoupler emitter output

I am trying to control a load switch from the GPIO pins of an STM32 which outputs 3.3V. They need to be isolated using the optocoupler shown. The problem is that the isolated voltage supplied is 24V, ...
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3k views

Using AC current to trigger Triac

I am trying to simulate the operation of an optocoupler with a triac to trigger the triac using the AC current. I have come across a few circuits that are all similar: My question is regarding the ...
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2answers
57 views

Optocoupler to switch 24V using Arduino

I am currently redesigning a circuit to switch a spring applied brake using an Arduino Micro. The current circuit looks like this (please excuse if I'm using wrong symbols, I'm learning by myself): ...
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241 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
118 views

Driving multiple loads with a single TRIAC and multiple optoisolators

I simulated this circuit in multisim. It is working fine. However, I am just curious to know if it is possible to drive multiple loads with multiple opto-isolators with single TRIAC? Something like ...
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Latching/Non-Latching Relay Driver Circuit with darlington optocoupler

I'm designing a circuit where an ESP8266 controls two types of relays, a single coil latching relay and a normal non-latching relay. The relays are power relays use to control low power electrical ...
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1answer
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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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Proteus simulation error

I am getting these errors while running simulation in proteous. [SPICE] transient GMIN stepping at time=7.87403e-006 [SPICE] TRAN: Timestep too small; timestep = 1.25e-019: trouble with node #00004. ...
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1answer
829 views

High side RC ESC switch

I've been designing a test bench for RC propulsion systems and for that I thought it would be nice to be able to switch the power to the ESC on/off. For this I designed a simple circuit which I ...
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4answers
294 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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1answer
65 views

Controlling AC load from a microcontroller GPIO with triac

I have the above question and I don't know who to ask. I looked around here, while most have no answers but there are a couple that kind of applies but went a little over my head, like these: ...
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4answers
114 views

how to reduce turn-off delay time of PNP transistor

I am having tough time while driving PNP transistor with optocoupler to generate 1KHZ PWM signal. my circuit consists of micro controller which will generate 1KHZ pwm signal which will go to base of ...
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1answer
41 views

How to control motor (1.5 V at about 0.5 A) with Particle Photon using optocouplers and transistors?

I’m trying to control a motor that runs at 1.5v at ~0.5A using a Particle Photon. I’m powering the Photon over USB (for now, at least) and the motor with a AA battery. I’ve tried designs based off ...
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0answers
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Opto-isolated RS232 signal capture

I have a problem in which I need to capture (spy on) an RS232 signal through an opto-isolator. This isolator needs to be high speed since the RS232 signal can reach up to 115200 baud. The main problem ...
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2answers
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what is the reason behind DC level shift of the optoisolator ouput(collector of photo transistor) terminal?

i am using SFH-610A optoisolator to switch 1KHZ PWM signal. on input side of opto i am triggering from micro controller with series resistor 500 ohms. and on the output side i have pull-up of 3.3V ...
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Buffering a Digital Microcontroller Signal for Connecting to an Optocoupler

I frequently work on projects in which I use optocouplers for isolating digital +5VDC control signals (for example, from a microcontroller) from the rest of the circuit. However, since these work by ...
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42 views

Is there such a thing as a (cheap) optocoupler with a non-polarised output?

Standard optocouplers have a polarised input and a polarised output, thus: It is possible to get a coupler with a non-polarised input, thus: However, what I require is an optocoupler with non-...
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1answer
20 views

Rise time of 6N136 opto-coupler

I am trying to use below circuit for convert 24VDC high speed pulse to 5VDC pulse that can interface to a stepper driver IC. I have used 6N136 opto-coupler and according to its datasheet it can handle ...
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1answer
170 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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2answers
102 views

Does a BJT optocoupler have an inherently short circuit proof output?

I want to use an NPN optocoupler (ACPL-214) to drive an offboard relay. I know how to size the input resistor to limit the LED current to 20mA. This will cause the output current to be in a certain ...
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1answer
120 views

Why can't I test the transistor part of an optocoupler using my multi-meter?

I attempting to test if my PC111 opto-coupler is working properly (pulled from a PSU). I wanted to use my multimeter first (so the device not connected to anything), setting the multimeter in the ...
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915 views

Does this optocoupler circuit work practically?

I've been trying to make a circuit that: Outputs 12V when the power is off Outputs 0V when the power is on. Input is 230V 50Hz AC. I have a question about the voltage across the output capacitor. ...
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3answers
73 views

TLP184 Optocoupler - Something is going wrong

i'm using this simple schematic (using a TLP184) in order to get the status of a reed/dry contact using an optocoupler There is no way to get it working, also if the connector pins are opened, from ...
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22 views

snubber circuit or opto isolator with relay

I have a relay module link with a built in opto-isolator circuit. When there is no load connected to the relays, the relays switch as expected. But when an inductive load (240V 0.5 HP) motor is driven....
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1answer
78 views

Opto-isolation amplifier output is too off

(As a follow-up to an earlier question answered by the community - thanks!) So I've got the test circuit setup using the HCPL 7520 (datasheet) now and planning to use an Arduino Uno to measure the ...
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3answers
55 views

Opto-isolation amplifier giving no output

First of all, thanks to the community for having such helpful answers here - don't post very often but here's one I could really do some help with. I want to measure a voltage range of 0-100V DC in an ...
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23 views

Reading isolated multichannel input with voltage drop on all channels

I am building a circuit to read atleast 22 input channels (24 vdc) using an Arduino board which essentially works on 3.3 vdc or 5 vdc. My current setup makes use of 22 PC817 optocoupler. I am sharing ...
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Optocoupler with phototransistor base lead

I'm thinking about using 4N25 optocoupler - it has a separate lead for base of phototransistor. How do I use it? I suppose I can't leave it floating?
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What's the reason for keeping a base line in optocoupler? [duplicate]

Image Source: https://www.vishay.com/docs/83725/4n25.pdf The pin no 6 of the optocoupler IC is connected to the base of the NPN transistor. Should I keep it open? Or grounded? Does it anything to do ...
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1answer
500 views

Overvoltage protection for AC relay dilemma

I am currently designing a safety-related device that has to open a relay when a certain event occurs. During most of its life, this relay will be closed, and only open if the safety event occurs, ...
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2answers
158 views

A question about using optocoupler instead of FET for longer signal wires

After my previous question I had concluded to use the following circuitry to operate this solid state relay: But now I found out that, from the micro-controller(Arduino UNO) digital output pin to the ...
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1answer
198 views

FT232R for RS-485 (DMX512) with Isolation - TX Optocoupler

I am trying to make a DMX controller board using the FTDI FT232R (FT232RL) chip for USB to UART and a MAX485 to output data over RS-485. I have a working prototype done, but for the finished product I ...
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0answers
21 views

characterize internal capacitor of optocoupler

I am reading article Using an automated Excel® spreadsheet to compensate a flyback converter operated in current-mode by Christophe Basso, Tomas Petrek/David Sabatié. In page 12, they explained how we ...
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39 views

Read 24 Vac signal with a Raspberry Pi

I want to read a 24 Vac signal coming from my old automatic gate with my Raspberry Pi. The signal tells me if the gate is OPEN->24 Vac or CLOSED->0 Vac. Raspberry Pi input are 3.3 Vdc tollerant. ...
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1answer
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Optotriac+triac: how do I calculate the gate resistor

I am building a small circuit to turn on/off a 200W heater. I am using a MOC3023 and a BT136. At the datasheet of the the ...
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1answer
66 views

Using multiple 4N25 optocouplers - Approach for compact PCB design?

I'm working on building an Ardunio Nano device that detects if automotive 12V circuits are on / off. I was able to successfully build & test a sample circuit provided Phil Frost. The question I ...
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30 views

Is it necessary to remove ground on all layers when using isolated DIO

So, I am using uptocouplers and digital isolators for a project connected to a microcontroller GPIO. I removed the ground (ground plane cutouts) under the load side of the components, is it necessary ...
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4answers
321 views

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

I stumbled upon this: Source. The MDB bus is communicating at a 34V level and the other side is at 5 or 3.3V. Why are they coupled with optocouplers rather than a voltage divider on the master tx ...
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1answer
35 views

How to extend optocoupler's common mode transient immunity to its Input constant current driver

Hello planning to use an optocoupler to interface a button meters away from the circuit. The optocoupler ILx series already comes with Common Mode Transient Immunity which would work great for my ...
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2answers
87 views

High or low side switching where the switch (button) is meters away from the circuit

I am making a circuit for a button to be far away from the circuit, about 50 meters round-trip. I have went decided to use an optocoupler to protect the uP from the worst of the outside environment ...

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