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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Optoisolator Long term Reliability at HVDC

Most optocouplers spend most of thier time isolating mains voltages.They are reliable doing this and they are cheap and simple.How would things go if the same garden variety opto was isolating a DC ...
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81 views

4N32 Opto-Isolator Questions

I am looking into using a 4N32 opto-isolator and am struggling to find information on its pin 6. This looks to be the base of the transistor (darlington). I see example circuits where they appear to ...
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1answer
231 views

How Zero Crossing optoisolator to work with 220VAC?

I want to use a H11AA1 to detect Zero Crossing, but I am not sure how circuit should look like. How much voltage should LED receive inside H11AA1? Here is datasheet: ...
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40 views

what is the best way to protect sinking inputs

I have a controller with sinking inputs ( should be grounded to activate) , I will use the system in a noisy environment, I want to protect these inputs from EMI and voltage spikes, what is the best ...
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366 views

Optocouplers with non-inverting logic

Here is the setup: I'm using the Arduino Mega's SPI functionality to send signals to multiple DACs. For digital isolation, I am considering the HCPL-2631 or the ACPL-064L. The problem with these two ...
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94 views

Power rating for opto-triac trigger circuit resistors

RHS will be using 220v 400watt bulb 2 simple questions 1- does the 360ohm resistors has to be of high watt too ? 2- all i can find is 5-10watt resistors, can i use them ? would they snub correctly ...
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112 views

Opto Coupler output voltage drop when connected to PLC

I have an input of pulse width 5 ms and which is fed to a Buffer IC and then the output of the buffer is FED to an opto isolator whose collector is pulled with a pull up of 7.5k resistor with an 24 V ...
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81 views

Using an opto-isolator in a car's circuit. How to ground?

So I have a microcontroller that will read some of the car's sensor output (0-5v) and i plan to send the signals through an opto-isolator. The problem is that when i simulate this, it seems i cannot ...
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81 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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104 views

uC-controlled high-side switch

I designed a circuit that powers on when the car is started (key is in ACC or ON). The circuit's uC then enables 12V from the battery by setting port PC5 high. The uC detects when the key is ...
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1answer
58 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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50 views

Exceeding _Enable input voltage_ of optocoupler

I have microcontoller board with following optocoupler interface which is obviously made for input up to 5V. Based on datasheet I found, Vf = 1.5 V and ...
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3answers
203 views

Recommended capacitor rating for this mains zero-crossing detector

I found this zero-crossing detecting circuit here I want to recreate it, using the parts that I have on hand (or can get cheapest), but I'm not sure how to choose the correct 0.1uF capacitors. ...
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96 views

Timing Issues with Optically Isolated Data Signal

I have been working on a system that requires data transmission between two devices powered by separate supplies. I have based my design on the MIDI-hardware Spec, as I'm comfortable working with that ...
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4answers
325 views

Opto-coupler output

I am using this circuit for mains detection: The output fluctuates a little but capacitor and resistor values ensure that Output is logic HIGH when 220V mains is present. Once mains is not ...
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2answers
140 views

optocoupler output protection

I've got this circuit. The target generates an identical PWM signal to control the intensity of 3 LEDS. But I would like to protect the output of these optocouplers with this TVS: I'm not sure if ...
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165 views

Hey I am using 2 4N35 Optocoupler from Visha can I replace them with a single ILD615 from Vishay?

I went through both datasheets and i think it should work. Basically I am asking if the dual channel version of 4N35 is the 8 dip ILD615. Thanks. edit: I have added the picture. my circuit is like ...
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121 views

normally open or normally closed OptoMos

In the following OptoMos datasheet the OptoMos is defined as Normally closed, when there is no input the output is closed. But in other OptoMos like the SFH618A-2 i can't find if the OptoMos is NO or ...
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78 views

How to use same 'input' for two circuits

First of all, please excuse my complete lack of knowledge in electronics :) Let's start with a little bit of context. I am trying to modify a machine that already uses a photo-interrupter to measure ...
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56 views

Adding resistor in parallel to digipot

I'm trying to control a device using a digital potentiometer (AD5245S). In my application I can't tie the low-ref of the potentiometer and ground, so I'm using an I2C optical isolator (ISO1541) to ...
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1answer
136 views

Converting 5 volts to 12 volts using a photocoupler

i have an arduino and i need to convert 5 volts to 12 volts in order to trigger a 12 volt Rele, i am considering to use the circuit that i attached here (below), if the "input" square is 5 volts, what ...
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58 views

Do I need TVS with Optocoupler relay

I am connecting digital output from a camera to a light source using a relay (see below). The relay uses SONGLE SRD-5VDC-SL-C Optocoupler: RELAY DATASHEET The camera manual says "Uses an ...
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101 views

Voltage Regulation

I am a young engineer and I need a help from you. I need to design a driver circuit which must power-up a LED (OC) if the measured volatge is greater that 50V (Voltage to be measured can be upto ...
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99 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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79 views

Severe Voltage Drop When Applying a Load to Opto-Isolator Circuit

The circuit below uses the Vishay ILD213T optocoupler (datasheet). The load in question is a 5V solenoid valve with a resistance of 46Ω. The circuit is configured with "IN1" connected to a GPIO pin ...
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198 views

Opto-isolator output from collector vs. emitter

I have an Isocom ISQ2X quad opto-isolator (datasheet) that I will use to drive a logic input. The opto-isolator's simplified model given by the datasheet is pictured below. The transistor base pin is ...
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245 views

Use a PC123 optocoupler for MIDI input

Im trying to connect a MIDI input cable to an arduino. To do that, I need an optocoupler, that secures the internal circuits from damage. This is the schematic as shown by the MIDI specification: ...
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111 views

Design of AC measurement circuit

I posted a question earlier, How to measure AC voltage without a voltage divider using microcontroller and I got some very useful answers, one of those was to implement this for isolation ...
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30 views

Optical switch operation point derivation

I have an optical switch part opb840W and I am failing to derive the required information for my application from there. The intended use would be as in the following circuit: simulate this ...
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551 views

What is the correct way to measure voltage with an optocoupler?

I'm using an optocoupler to measure a voltage, I'm making a current loop to control the current through the LED, so I'm using three op-amps: one to measure the voltage, one to set up a current offset ...
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2answers
287 views

Driving a 24V isolated load from a 3.3V MCU

I am looking to drive a 12-24V purely resistive load from a 3.3V MCU. I would like to use an opto-isolator to separate the circuits electrically. I've drawn up the following circuit, but I'm not ...
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52 views

Accidentally outputting to an optoisolator

It's your friendly electronic hobbyist again. I am designing a board where I am reading input from an optoisolator like this. IN7 is connected to a peripheral parallel port chip of an old 8-bit ...
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115 views

Isolated mosfet switching circuit

I have designed the circuit below for a isolated digital output from a mcu. The switching speed is slow -- only 100ms or so. I would like to be able to switch between 3 and 24Vdc at about 1mA to ...
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150 views

Combining Optoisolator and Relay into one I/O pin

I have a project that uses two microcontroller pins to control the input and output of an isolated device. The LEDs are for status, showing when an input or output is enabled. I'd like to save some ...
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1answer
86 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 ...
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80 views

How to isolate Data / GND between WS2811 LED IC and MCU

How do you isolate the Data and GND lines between an MCU and a WS2811 LED Driver IC? The W2811 is another system that I will be interfacing and need to maximise protection to this. Bandwidth is not ...
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60 views

Switching two optocouplers based on different voltages

I want to build a (I think) simple circuit where I want to transmit the state of two switches across two wires (ground and live). Let's say I have a circuit with which I can set three output voltages ...
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130 views

Multiple ground planes with optocoupler

I'm designing a circuit that uses an optocoupler to isolate a relatively noisy H bridge from the USB circuitry also present on the board. Clearly in this case I will have two grounds - what is the ...
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61 views

In the given circuit of a regulated power supply, why is error computed twice, i.e., before and after isolation?

Circuit Operation \$R_4\$ and \$R_5\$ constitute the potential divider which is fed to the error amplifier \$A_1\$. The reference voltage is generated by the Zener diode \$Z_1\$. The error signal is ...
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249 views

What are the differences between optoisolator output styles?

Digikey lists optoisolators with several output types: Darlington Darlington with base Photo FET Photovoltaic Photovoltaic, linearized Transistor Transistor, with base What are the differences ...
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132 views

Opto-characteristic for schematic

I am referring below circuit, where I am using P781 opto-isolator. H1G is I/O pin from LPC2138 controller.( VCC for LPC is 3.3V ) J24: 12V,6W Heater Link for opto datasheet: ...
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109 views

When to use or not an optocoupler

I understand the benefits of optocouplers. Always when I'm designing a microcontrolled motor control I isolate the mains from the MCU with those devices. On a few designs I did without the optical ...
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81 views

Optocoupler Rf calculation

I am using FODM124 optocoupler. And I want to work in Saturation mode. How to choose VF,IF,CTR and how to calculate Rf?? Bcoz i am seeing different IF's in the datasheet for different Vce's? What ...
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219 views

LM358 Op amp problem

simulate this circuit – Schematic created using CircuitLab simulate this circuit Right now my configuration of my circuit is this: http://i.imgur.com/2x5nGcf.jpg The only ...
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1answer
306 views

Calculating resistor values for RPi circuit detecting AC current using H11AA1 and PNP transistor

I've got an electronic doorbell system (Aiphone IE-1AD) that sends a ~15Vac signal when the button is pushed. I used this blog post on detecting a signal on a similar door bell using a moteino ...
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121 views

Voltage drop problem?

I made a circuit using PC817 optocoupler. On its 1st pin, i gave 3.3v, 2nd pin was ground. 3rd pin was 12v and on 4th pin i used a pull down resistor with resistor ...
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534 views

Difficulties with using LM358 Op-amp

Basically (Although I'm using an LM358 op amp): Is what I'm trying to design, if I change the current source from the 48uA to 8uA the output on the simulation changes but the output does not in ...
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225 views

Will this schematic work?

Newbie here, trying to learn electronics (Iam from SW background). Looking for someone to review the initial schematic and advise. Haven't ordered the parts yet, so appreciate any tips in finalising ...
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269 views

Optoisolator with Logic Output - How To Use IC Circuit Example?

I'm looking at an Optoisolator with a Logic Output..It's an optoisolator with a Schmitt Trigger on the output. I think the datasheet is a little bare for my comfort level, so I'm looking for some ...
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233 views

Low Pass Filter For Square Wave Through An Optoisolator

I've got a higher voltage square wave input that I'm feeding through FOD817B Optoisolator. The square wave frequency is in the range of 30 to 300 Hz. The Circuit is like this: simulate this ...