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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5answers
13k views

Using an Opto-Isolator to detect 120VAC on a Microcontroller

I am designing a system where I need to know whether or not 120VAC is present on a specific wire. The system is in line with a fuel pump system, and I need to check to see whether or not the pump is ...
4
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1answer
741 views

Determining the input current of an optoisolator based on output current and CTR

I have an optoisloator (CTR min:20% max:400%) in my circuit whose output current (Ic) is around 10 mA. To facilitate this much output current, how to decide the input current(If)? whether i have to ...
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1answer
482 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 ...
3
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1answer
820 views

Combining dirty 12V inputs with delicate micro controller

I'm building a (LED) blinker circuit for my motorcycle. It will have the basic on/off blinking for left and right (J1 & J2) and an "emergency" mode (J3) for more "aggressive" LED blinking, which ...
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3answers
807 views

Connecting a Camera Hot Shoe to a homemade strobe

The Situation simulate this circuit – Schematic created using CircuitLab I need to trigger a strobe from a Sony Hot Shoe. A 3.5mm jack lead comes out of the hot shoe. Using a multimeter I ...
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3answers
11k views

Did I use this optocoupler correctly?

I'm planning on using this optocoupler in a PCB I'm making. I've never used one before so I want to make sure I'm doing this correctly and got the right numbers off the data sheet. The image below ...
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2answers
1k views

Efficient method for isolated detection of AC voltage without a stepdown transformer

What is an efficient method to detect the presence of Line AC power in an isolated method? My first thought would be to use an optocoupler, but in order to do that, you need to supply the current ...
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1answer
1k views

DC Motor control Optocoupler

My current project does involve some DC motors which I have to control the speed of. I'm will probably use the PWM pins of my arduino mini for this. Currently I am building my first prototype of the ...
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1answer
268 views

How to adjust output resistance with galvanic isolation?

I need to control the device (lighting LED driver) with 0-10V input. It looks like the driver has 100 uA current source as it can be controled with 0...100% PWM, 0-10V or 0-100kOhm resistance: So I ...
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2answers
1k views

Solid state relay (or equivalent/alternative) to drive 6V DC from a 3.3V micro

I have to open/close two wire from a closed device. I cannot open due to it's under warranty, and the only part that I can open and modify is an external button that connects the two wires. Firstly I ...
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4answers
8k views

How to convert a digital signal from 5V to 24V?

I have an industrial application where I have to interface a microcontroller output which gives a digital signal (0V to 5V) on its outputs and I want this signal to control a relay which takes (0V to ...
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6answers
9k views

How to detect 220 VAC voltage using an opto-isolator

I created the following circuit. I plugged it in and it works!! Now I thought of adding an opto-isolator to the circuit in place of the LED. The value of C was the same. $$ X_c = {(({220volts-1....
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2answers
729 views

When should I use opto-isolators and isloated DC-DC converters?

I am using multiple DC-DC converters to obtain 12V and 5V. Shall I use non-isolated or isolated converter for Arduino's? From what I have read so far, isolated are used when you have inductive loads ...
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3answers
4k views

How to design an optocoupler circuit for raspberry pi

I want to give sensor pulse to raspberry pi. The sensor signal comes from a running conveyor . The sensor gives 24v signal hence I used a optocoupler to convert the 24v to 3.3v . How should I design a ...
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1answer
1k views

OptoIsolator Reliability?

I have heard it from multiple people over the last 5 years that Optoisolators are failure prone and should be avoided when able. I'm working on a project (for personal use) that I was going to put an ...
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2answers
213 views

Optocoupler Question

I'm currently trying to create a system to open my apartment's door (using the buzzer) using my raspberry pi, and thought that using an optocoupler would be the best solution - although I'm a complete ...
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4answers
3k views

4N35 opto-isolator for MIDI input does not work?

I have the following circuit which I would like to use to connect a MIDI enabled device. I am not getting any signal on pin 5, could it be because the resistor from the base to ground in too small? I ...
6
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2answers
2k views

How to eliminate Bluetooth noise in electric guitar

After learning more about this problem, I have continued this question here. I am trying to remove noise from an electric-guitar circuit that I have created called the ArduGuitar. My circuit ...
6
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3answers
4k views

Isolating motor control signals from microcontroller from high voltage/current lines

We need to design an integrated DC motor controller/driver, which will be under microprocessor control. Due to space requirements, either the digital and analog circuitry will be on a single PCB (...
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1answer
5k views

How to sense 24V AC (Thermostat) with a 5V Microcontroller

I'd like to detect thermostat events (heat, fan, ac etc) with an Arduino. I've done quite a bit of investigation but haven't found a definitive solution. Most projects I see involve controlling the ...
4
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1answer
1k views

How to select a good optocoupler for uart to 20 mA current loop converter?

I'm trying to make a circuit that converts UART signals to 20 mA current loop signals. I tried this circuit to switch the signals. I am not much experienced in optocouplers I had just two types to ...
4
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3answers
561 views

Normally Closed Optoisolators

I understand that typical optoisolators can logically be considered as "normally open". However I have a situation where I'd like the circuit controlled by the opto to be normally closed, mainly for ...
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2answers
837 views

Optocoupler driving 300mA continously (or use darlington topology?)

Looking at driving two LED strings with a DC/DC constant current LED driver module. The constant current side can't be referenced to ground of the control circuit, so I need to have an isolated ...
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2answers
560 views

how do I use H11L1 correctly to receive MIDI?

I was following this schematics. This is the first result on google images My Arduino Serial Monitor received nothing. I tried to replace the H11L1 with LED, and it does blink. but as soon as I ...
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1answer
823 views

Driving a 24VAC solenoid with arduino using a octocopuler and a triac

Following a previous question I have redesigned my schematic: I'm trying to energize a solenoid used to open and close a 24VAC sprinkler valve I have the following questions : 1) The GPIO leg can ...
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1answer
122 views

Understanding the difference of optocouplers vs relays and choosing the right replacement

I'm a bit overwhelmed by the sheer amount of variations in optocouplers and since I've never used one before in any project I don't really know what criteria to look out for. A colleague of mine ...
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2answers
1k views

What is a reasonable isolation voltage for an optocoupler/digital isolator?

I need to isolate an input from my processor. What is a reasonable isolation voltage to look for optocoupler/digital isolator? I've pretty much decided to go with an RF isolator at this point because ...
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1answer
10k views

How to use a phototriac coupler to trigger the main triac?

I have in my box of parts a phototriac coupler, namely a Sharp PC3SD21NTZ (datasheet), which is a zero cross type. I don't know how to use it, but I've been meaning to learn for a while. This part is ...
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3answers
312 views

Problems sizing series input resistor for this optocoupler

Under the electrical characteristics, the optocoupler 4N26 typical "forward voltage" is given as 1.2V. But for sizing the input resistor Im have hesitations. In my application as a control signal I ...
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4answers
505 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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4answers
1k views

What's the difference in a digital optocoupler and a non digital

I'm looking at 2 different optocouplers.The Avaago ACPL-K44T and the ACPL-227. The ACPL-K43T states that it's a digital opto-coupler while Avago ACPL-227 doesn't. Schematically, they're a bit ...
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4answers
265 views

Is this line detector safe?

I'm thinking about building a basic AC mains voltage detector. I'd like for it to be both protected and isolated, so I have a zener TVS and an optoisolator. R1 and R3 are chosen so that between them,...
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2answers
3k views

Detecting Zero Crossing of Mains (Sine and Square Wave)

I need to design a circuit that can measure and output pulses for a MCU at zero crossing of 220VAC waveforms. The application requires that that both square wave waveforms and sine-waves should work. ...
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4answers
35k views

How to connect a Inductive Proximity Sensor Switch NPN DC6-36V to PIC18F4550 5V

I have got a LJ12A3-4-Z/BX Inductive Proximity Sensor Switch NPN DC6-36V with this Specifications: Model: LJ12A3-4-Z/BX Theory: Inductive Type Sensor Wire Type: Cylindrical DC 3 Wire Type ...
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1answer
397 views

Totem pole opto-isolator TLP152 won't work as intended

I've been working on this very confusing problem regarding making a TLP152 opto-isolator to work as intended. Here is my circuit using a TLP152 to work as a IGBT gate driver. TLP152 circuit diagram ...
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1answer
94 views

LEDs and high currents

In smartening up my doorbell I've been playing with my illuminated pushbutton and have fallen into a bit of a rabbit hole. The doorbell normally: simulate this circuit – Schematic created using ...
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1answer
126 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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4answers
2k views

Shematics: optocoupler controls a transistor and doesn't work as expected

I'm applying optocoupler TLP521 to decouple microcontroller Atmega88 (on the left of the schematics) from the power circuit. I have a problem understanding why the schematics below doesn't work in ...
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1answer
151 views

Sense 230V - voltage

Brief sum up (you can go directly to the end if you already read the sum up in the other question) For a home project I'm making a controller to drive a two-direction 230V motor. For those unfamiliar ...
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1answer
188 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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3answers
130 views

Optocouplers vs Voltage Dividers

I have a device that has a terminal that goes to 5v at certain times. I wish to sense that voltage with an ESP32. I have built this circuit using an optocoupler: simulate this circuit – ...
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1answer
5k views

Protect PC817 Optocoupler Anode from High Voltage

Voltage at IN3 will vary from 10V to 28V, How can I protect the optocoupler from getting damaged due to high voltage. What is the maximum voltage and Minimum ...
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3answers
6k views

Zero crossing detection and Light dimmer

I am confused by zero crossing detection of opto-triac. I know what is the zero crossing detection or switch. (ZCS) Zero crossing detects what is the point that wave is going to positive to negative ...
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1answer
599 views

Isolated closing contact other than relay?

I need an isolated closing contact, like a relay, but ideally solid state. Rating 24V 100 mA on the contact side would be plenty. 1 kHz operation would be enough as well. I will drive this from 5V 25 ...
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1answer
587 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
3k views

What is “Saturated CTR” of an optocoupler?

For example, in the datasheet of 4n27: . So what is saturated and what is non-saturated CTR?
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2answers
1k views

Debugging a garage door opener circuit with an optocoupler and mosfet

There seem to be many related questions, but I can't quite find the answer I'm looking for. I've got a garage door opener switch. There's 16V across the wires, and when you short them, the garage ...
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1answer
2k views

high speed optocoupler circuit

I have 4n35 optocouplers, I am using these to isolate a motor driver circuit and the Arduino controlling it. I put one on the slave select pin and one on the tx line to the motor controller (there is ...
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2answers
916 views

Optocoupler w/ RasPi & Door Buzzer

I'm currently trying to make a system where sending a message to my Raspberry Pi from my phone will send a signal to my apartment's buzzer to open the front door, however I've been having problems ...
0
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2answers
2k views

Opto-coupled PWM output

I have a circuit with two different ground levels. Using a optocoupler, I want to translate a PWM signal to the new ground level. Does there exist a easier method than the following? (Ideally with ...