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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Q: 4 Channel Optocoupler to convert auto 12V signal to 5V Arduino

I'm trying to connect an Arduino to my car. I'm planning on using the switched 12V (potentially 11V to 14.4V) car system as inputs into the Arduino. The Arduino will be running on 5V, provided by a ...
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60 views

How can I suppress transient HIGH signals in an opto-isolated digital circuit with pullup resistor

simulate this circuit – Schematic created using CircuitLab I am recording an opto-isolated signal using the opto-isolated output described here: http://softwareservices.flir.com/BFS-U3-04S2/...
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42 views

Designing IGBT driver: question about datasheet specs

Summary I'm trying to design a driver for a high voltage, IGBT driver, using an optocoupler for isolation, and have a question about whether this design is compatible with some of the numbers in the ...
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60 views

Solid state relay versus n-MOSFET for controlling large loads with a microcontroller?

Let's say I'm trying to control a relay using a microcontroller. This relay requires a 500mA input current which is too large for a microcontroller to drive. It seems like I could use either a n-...
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Are these the right capacitors for this optocoupler?

I want to sense mains with an ESP32, for that I am planning to use an AC optocoupler and add some capacitors to smooth the signal. This is my schematic: Sense3 and ...
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255 views

How to implement a ground loop isolator in an audio circuit that connects to USB and line out of a laptop?

I'm working on an audio interface that utilises a microcontroller and a CS42448 audio codec. When receiving USB power and receiving audio from a laptop, there is a ground loop. Otherwise, it works ...
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62 views

Isolated UART communication with optocouplers

I want to create a universal PCB for projects requiring galvanic isolation. I'm not in need of fast baud rates, 9600 should suffice. My most common use will be with Arduino 5V/3V3. I want to ask if ...
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35 views

How can I establish a transfer function for an optocoupler + amp circuit?

I have a simple analog circuit which takes a large reference voltage and outputs an isolated, small, scaled voltage. I am trying to establish the transfer function for the circuit for calibration ...
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74 views

Optocoupler relay, one power source for both relay and microcontroller

I'm having a project, there will be a 16 relays (Lights), which are controlled by 16 buttons. I'm using esp32 as Micro-controller. For achieving this, I've used two mcp23017 boards as GPIO extenders. ...
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47 views

Isolated Switch

I have three question on designing Isolated switch (Protected Microcontroller and from accidentally inserting power) Does it matter which side is the switch - on 15V(Isolated side) (image 1) side or ...
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44 views

How I can perform accelerated testing of my PCB board by own?

I am working on a project in which there are system components listed below as module: 8 ultrasonic sensors 12-30 V (Sensor module) 3 DC motors (Drive module) 35 V to 5 V buck converter and a 35 V - 5 ...
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79 views

Optocoupler circuit to shift from 3.3V to 15V

I am trying to use the circuit below to shift a squared wave form (2kHz) with a peak of 3.3VDC to one with a peak at 15VDC. I am trying to do that with the circuit below, I am using the optocoupler ...
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54 views

At what value should I choose the MOSFET resistors for the MOSFET triggered by the MCU?

I have added a picture of my circuit. Vcc = 5 V and Rled = appr. 600 Ω. So, I_Rled_current = 6-7 mA. The MCU is an ATmega328p. MCU pd1 and pd2 are logical high and logical low. What should the values ...
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111 views

Control a 120 Vac relay with a triac. Good idea?

I'm beginning the design of a light control system based on a microcontroller. This is to activate the lights, what is usually used are continuous voltage relays, in ranges of 5, 12 or up to 24 VDC. ...
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49 views

Is it possible for this kind of solid state relay to drive high side?

I require a solid state relay to be able to switch high side, but also has low on-resistance. G3VM has low on-resistance but it's application diagram shows exclusively low-side switch. Question: ...
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50 views

Indicator LED on Optocoupler Circuit

I want to add an indicator LED to an optocoupler circuit I made so I can have visual feedback for when the opto is being triggered. Originally I hade wired the LED in series with pin 1 of the opto, ...
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61 views

Optimal LDA210 optocoupler circuit for mains detection

I am trying to sense mains with an ESP32. For that I plan to use this circuit: I want to optimize the resistors from If current in order to lower the power (W) they use so they don't get hot. ...
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296 views

How do I properly interpret identification on opto-isolator IC?

Lightning struck near my house and destroyed a bunch of things I had plugged in, including a treadmill. I swapped parts with another one and identified that it's the lower motor control board that is ...
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38 views

What is the difference between LDA 210 and LDA 212?

Do you see any difference between LDA210 and LDA212? Can it be that a factory produces the same product with different names? LDA210 datasheet: link LDA212 datasheet: link Official comparison ...
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1answer
78 views

Are 4N35 optocouplers clamped at 22V?

I am trying to detect mains with an ESP32, for that I started testing this circuit: I bought a 4N35 optocoupler and 110kΩ resistors. My first test was using 2 resistors in series, so R1 = 220kΩ. The ...
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52 views

How to know which opto-coupler is suitable for high current application?

I would like a suitable opto-coupler to use as isolation from a 12V and around 30A current and another for 5V and around 30A. Are there any good opto-couplers for those ratings?
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458 views

How can I do a heatsink calculation and determine whether a heatsink is required or not?

I am designing a DC solid-state relay using an FQP30N06L (a MOSFET with 32 A, 60 V, Rds(on) = 0.035 Ω @Vgs = 10 V) to control using a Raspberry Pi. I am trying to control an electric door lock with 6-...
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58 views

Isolating low-current, low-voltage digital signals

I'm working with a battery-powered sensor that allows reading its measurements using two digital signals - a clock and a data line. The clock speed is abount 3kHz. In addition to those two signals, ...
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104 views

Is 24V enough to power this optocoupler

I am using this proximity sensor (E1 NPN) with a Raspberry Pi. The sensor outputs a 24V signal when triggered, which I need to step down to 5V so as to not blow out the Pi. My plan is to use this ...
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38 views

Measuring voltage on different ground reference – PV

I have a small solar power installation and I want to monitor all the data from it. My only problem left is that the solar panel input doesn't have common ground with batteries (or atleast there isn't ...
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131 views

Optocoupler for Ethernet connection

First of all sorry about my English, it's not great. Second of all the question: I want to create a unidirectional Ethernet connection between my laptop and desktop! For that I created a circut like ...
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72 views

What are the disadvantages of using NZC Optocoupler as switch

I've bought some MOC3023 to use with a triac for turning some home appliance on/off using an EPS8266. The thing is.. every place that I search says that for on/off the best is a zero crossing detector ...
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123 views

Do I need any resistors on the outputs of my optocouplers?

I came up with this circuit: The idea is that I have this resistor ladder at the left that creates 8 different voltages between 0 and 24 V and I have 8 optocouplers that can switch one of these ...
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47 views

galvanic isolation in high voltage applications

consider a high voltage transformer outputing 100 to 200 kilovolt to a load, both in some oil container. the voltage needs to be regulated through a high ratio divider feedback path. the whole system ...
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118 views

How to know the minimum LED current of an optocoupler?

I am going to need to use an optocoupler to isolate two circuits in two situations. In both situations, a MCU GPIO will be driving the LED of the optocoupler to send a signal on the other end. I am ...
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55 views

Relay is switching by touching optocoupler with finger

To switch a 12V relay with a micro controller, I designed ("borrowed") this schematic. Build the pcb and it works great. But there's a little bug that got me a bit worried. If I touch the ...
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126 views

How to measure AC voltage using non-linear opto-couplers?

I am designing a TRIAC LED dimmer circuit. Depending on the AC voltage applied, I control the gate trigger angle for the TRIAC to reduce/limit the current at 15 amperes to the load. Gate trigger ...
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67 views

Briefly switching a coil

We are going to build a telegraph which can communicate to an other telegraph. One of our communication systems exists out of a bell. The idea is that the sender can press a button and the receiver ...
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90 views

Is using opto-couplers a good idea to switch in between two 80 pin connectors?

I am trying to implement a switch between two 80 pin connector outputs so that I can activate the desired connector. There are high speed signals to be taken into account. Is using opto-couplers a ...
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74 views

Need circuit modification for using a PC814 opto coupler to invert relay operation

I have tried every possible way but was not successful for the operation required. When AC Power 220V is fed to the PC814 optocoupler, the relay should turn off. Please suggest modification in ...
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139 views

Can a pullup be placed on the LED input of an Optocoupler?

The diagram is a minimum example R1 is the series resistor for the optocoupler's LED. R2 is a pullup that's absolutely required there for other components. Will the pullup be overcome by the ground ...
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66 views

Losing 3V in optocoupler + MOSFET circuit

I have assembled the following circuit on a breadboard (I've submitted an Eagle schematic because I've read that this place doesn't like Fritzing layouts. Despite watching a number of YouTube videos ...
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53 views

Optocoupler pull down resistor

How to use optocoupler pull down resistor at forward converter? I have to use pull down resistor, because I have to use to TL494. Vo=25V Vo.sen=2.5 CTR=0.8. Are there any rules?
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How to calculate resistors for an optocoupler?

I am a self-learner (for now) on electronics. I am trying to understand how to calculate resistor values when using an optocoupler and an ESP32 For my little project I want to sense several 220v wires ...
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Optocoupler relay driver - Help needed

I build the following circuit found in some websites, and the relay is on without applying any voltage to the optocoupler. These are the details: The relay's coil resistance is 720R. As soon as I ...
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77 views

Low-cost isolated power supply for optocoupler LED [closed]

I'm looking for an isolated power supply with the intention of driving the LED of an opto-coupler. The voltage regulation is not important and current output needed is not high. Cost is a major factor....
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What is the purpose of using an analog optocoupler?

What's the purpose of using an analog optocoupler in this circuit? Why not a digital one? An industrial battery charger. Normal operating voltage to monitor ranges from 120 V (Battery low) to 180 V (...
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65 views

Better to Opto-Isolate on Sending or Receiving End? Isolating to Avoid EMI

I am working on an art project using some modified bug zapper circuitry to produce loud and bright sparks. I have the circuit working and the sparks are very impressive, but I'm running into a issue ...
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218 views

Alternative to optocoupler in circuit design

I have designed a circuit that drives a +/- 20 to 30 peak to peak external signal received as an input to 16 different outputs. Another requirement is that I have to be able to switch the state of ...
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153 views

Replace 5V relay module with 3.3V relay

I'm working on an electronics project that was using an Arduino to drive a 5V relay module specified here. The relay switches a 240V AC (upto) 10A load. I have now moved to using an ESP32 which uses 3....
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OPTOCOUPLER EL817S1 OUTPUT 24V

is it possible optocoupler EL817 wiht input 3.3VDC and output 24VDC like below circuit. and if it possible what is the suitable value for the resistor
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Circuit to turn everything above 1V into logic level HIGH (5V)

I have a LED in a car and I want to hook up onto it to detect when its on. But voltage for that LED can depend on the intensity of the LED (depends if its night or day). I've measured voltages from 1....
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50 views

Using a specific optocoupler to turn on relay

I have already done research on how to turn on a relay with an optocoupler but I am still confused on some aspects. My diagram works great even though I am doing things incorrectly. simulate this ...
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334 views

How do I simulate a short/open circuit in LTSpice?

I am trying to simulate open/short conditions for testing an optoisolator circuit I'm building. Essentially, I need to simulate SHORT and OPEN in order to verify that what I'm designing will output ...
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61 views

Divide Hall effect sensor input

I've made a circuit which is supposed to take the output of a Hall effect sensor and divide by 5, so that I get one pulse per revolution of a motor. The motor is a Nidec FY9S40 variant. Since the ...

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