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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78 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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146 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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113 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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171 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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121 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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96 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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184 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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63 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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383 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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103 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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123 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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141 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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121 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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311 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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78 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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138 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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47 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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49 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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69 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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44 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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53 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
60 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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223 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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221 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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61 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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248 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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155 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
154 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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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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62 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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38 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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282 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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106 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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160 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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73 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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96 views

Transistor Reverse Biasing - AC

I am working on a project which require to activate a 24V Rated relay using a 3.3V rated IO. To provide adequate isolation I have added a Opto-isolater stage. In order to increase the current output ...
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129 views

Detect phone call termination

I am designing an automated telephone circuit that will work with the PSTN line. I already had a question to detect the incoming ring signal. Now I want to detect whether the opponent person in the ...
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1answer
211 views

Operating a 24VAC solenoid with a Triac. Protecting with TVS DIODE, RC Snubber or both?

As part of a project I am controlling 24VAC solenoid sprinkler valves like this https://rayshobby.net/wordpress/understanding-24vac-sprinkler-valves/ using a triac (BT1308W) http://www.mouser.com/ds/2/...
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301 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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536 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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96 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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222 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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43 views

Isolate a digital signal that changes its amplitude

I have to isolate a digital signal that has the following characteristics: frequency: between 1 and 1000 Hz amplitude pk-pk: 12V offset: 0-6V With "offset" I mean the actual voltage may change from ...
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130 views

Component values

Can somebody clarify the following points for the MOC3041 sample circuit given at their datasheet: What are the wattages of resistors at the HOT side What is the difference between 360Ω and just 330 ...
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152 views

Is this optocoupler front-end safe?

This is a follow-up to Is this line detector safe? I'm re-designing the front-end based on some great feedback from the community. I've decided to move to the following topology: The phase of the ...
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252 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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812 views

Measuring individual cell voltages in a series cells Battery

I'm making a 600V battery, and I'm trying to design a Battery Monitoring system, that measures (and keeps log of) each cell's voltage turn by turn, in a series configuration of 162 lithium cells. 162 ...
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411 views

Creepage Distance in Altium Designer

I have a design with a high voltage and a low voltage part. Between the two I need to have a creepage distance of 8mm. Some optoisolators I use in my design are not wide enough on the PCB footprint, ...
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75 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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362 views

TRIAC won't turn on/turn off

I'm trying to make simple lamp switching circuit to work, but it just doesn't want to work as intended - question is, why? I'm using MOC3021 random phase optotriac with BT136/600E sensitive gate ...