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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Optoisolated PWM control of resistive and inductive load using Arduino

I want to design a circuit capable of controlling the voltage of either a inductive (electrovalve) or resistive (heating cord) load. I want to have a variable voltage for these loads: for the ...
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MCU not turning on via high side PMOS or PNP BJT

This board basically senses 24vac and drives a relay using the attiny10 as delay timer (already tried 555). The board will only be driving a few's led's < 12ma and a 5v relay with ~40ma coil ...
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Transmit changing shunt resistor voltage value using analog optocoupler

I would like to use the IL300 to transmit the voltage of a shunt-resistor. The voltage value of the shunt changes between 0 up to 1 volt in 1ms depending on the load. On the receiving side of the ...
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How many optocoupler outputs can I stack in series?

I have 44 devices - each which provides a 5V output when active and operating correctly and 0V when not. On my microprocessor, I need to check if all 44 are active or not (don't need to know if ...
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Flyback: opto/Zener feedback circuit

Could someone explain the difference between these two flyback feedback circuits, and how the second circuit works? Any application note available would be a favor for me.
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BT136 TRIAC waveform

I am using a TRIAC to switch an AC signal (a typical example is shown in question Triac Switch Circuit using MOC3021 and BT136). When a BT136 TRIAC is used to switch a pure sinewave signal, I want to ...
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How to find a fast optocoupler (or how to read the datasheet)

I am looking for an optocoupler that can sustain a 400kHz signal. Now the question is how can I find out from a datasheet whether it does? Looking at a typical PC817 datasheet I see the following ...
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How can we explain this strange phenomenon with an optocoupler switching?

Two optocouplers are connected according to the circuit below. The input voltage across the first optocoupler is a true square wave (3.3 V amplitude). The first optocoupler is an open collector output ...
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Do I need a current limiting resistor with an industrial rail DIN optocoupler?

I'm going to use this industrial opto-coupler: Optocoupleur RS PRO, montage Rail DIN, 6 mA In its specs document they don't mention the need of a current limiting resistor. I always add a current ...
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NPN transistor on optocoupler ground catching on fire

I was experimenting with ways to cut power to my board and so I added an NPN transistor on the low side of an optocoupler (Q202.) I noticed my voltage regulator was oscillating from 3.3V to GND every ...
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Linear Analog Optocoupler Arrangements

For optocouplers with a second photodiode for feedback for linearization, what is the functional difference between the two positive input stage configurations below? simulate this circuit – ...
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How to isolate (and transmit) a 0-5V DC analog signal using an optocoupler circuit

I am trying to isolate control signals that are used to remotely operate a variable frequency drive. One is a 0-5V analog voltage signal that give the VFD its set point. I understand that optocouplers ...
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Optocoupler or DC/DC-converter for generation of trigger voltage

In my project I would like to trigger an external device with my electronic trigger system. The trigger voltage of the trigger system is 5 V, while the external device needs 24 V to be triggered. In ...
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Low Side Parallel MOSFET Drive [closed]

I'm doing a 12V to 230V push pull inverter design & need to drive it via two MOSFETs for each transformer tapping. Mosfets feeds by an optocoupler PC817. The frequency is 50Hz coming from a PIC ...
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Optocoupler necessary when grounds already common?

I have a 24V solenoid device, that is able to push and pull a small pin, that I would like to control with a 5V micro controller. The solenoid has a reed switch connected to 24V that indicates whether ...
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Problem with optocoupler + MOSFET circuit switch

I am trying to design a simple LED switch controlled by a GPIO on an STM32. I have designed the following circuit but it doesn't work as expected: GPIO and MCU_GND are from the microcontroller. From ...
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Would this isolated AC peak voltage detection circuit work?

I have adapted the circuit from Michael's circuit in Efficient method for isolated detection of AC voltage without a stepdown transformer to detect on either side of the positive half-cycle peaks, ...
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Why TRIAC is not triggering?

I'm trying to trigger a TRIAC BTA16-800 using an MCO3021 optocoupler. I have a two-channel power supply, in one of them I'm pulsing the optocoupler at 120 Hz and the other channel is configured as a ...
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Ideas for protecting the input of an opto against high reverse voltage

I've been given a circuit to test and pointed out that the potential reverse voltage across the led in the opto will exceed the spec. The cct is a dual input with an opto on each channel, which feed ...
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Does this two opto-isolators circuit versions work the same way?

I'm doing a circuit to control a 10W Led driver by an MCU, and I need both circuits isolated from each other. So I need one pin from the MCU to control the led brightess by PWM (Arduino normal PWM ...
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What does the VCC pin do in this Optocoupler?

I have this optocoupler, and I am trying to figure out how it works. What is the VCC pin supposed to do? How does it supply current to the gate pin of the transistor? https://www.digikey.com/en/...
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Circuit and layout review -- micro controller multiple outputs and different voltage domains

I would be happy to get feedback on a small circuit that I am designing. (Disclaimer: my experience in circuit design is limited and I not the most proficient person in using the design tools, so ...
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Recommendation for optocoupler for SCR and TRIAC Gate driver

I want to use an SCR having gate current "Igt" = 50mA and a TRIAC with Igt = 50mA to 100mA. I am looking for an optocoupler IC to drive the SCR and TRIAC. I saw MOC3021 but it's "LED ...
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How to design configurable optocoupled I/O

I am designing an I/O board based on the RP2040. One of the design requirements states that I/O terminals must be isolated hence I'm going for optocoupled I/O using something like 6N137S1 or similar. ...
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Best option for isolation of output voltage from controller board?

So I have the following schematic: I have a 400V output voltage which I have stepped down to less than 10V using resistor dividers in order to measure via DSPACE 1104 board(https://www.dspace.com/en/...
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Current consumption of a tachometer circuit

I am trying to determine how much current this circuit will draw under rest conditions when the Ign- is at roughly 12.5V. Would current run through the blue path? Sourcing from Ign- passing through ...
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Isolation high side MOSFET

I have high side MOSFET component VN7003ALH, with the following information, it has an input pin instead of a gate. As the electrical specification shows, the MOSFET drain and source voltage adjust ...
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SSR failed close and did not respond to commands (possible overheat). A day later, it works again. Why?

A cheap SSR rated for 40A is used as a switch for 2x 4500W heating elements in parallel (around 36A). It is used in 0degC temperature with a heat sink that might not be large enough. After 2 hours of ...
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Creating truth table

I want to create a truth table to see all options for 74HC123 output. Basically an optocoupler output is connected to 74HC123 as input. 74HC123 will get the data from optocoupler. There could be two ...
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How is output current of a MOSFET gate driver controlled?

So I have been studying a lot about gate drivers, and I understand calculation of the current requirement, but what I don't understand is how the output current of the driver IC regulated. In ...
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Is there anything wrong with this SSR circuit?

I am a mechanical engineering student currently interning at a small company. We make solenoid valves and some tests require that we cycle the valves many times. This is a circuit that I came up with ...
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5 answers
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Optocoupler Input or Encoder Output Problem?

I have this basic circuit but it's doing my head in with the actual prototype: When LINK is open (not connected to the optocoupler), Encoder output works OK - it goes 0V and 5V. Also while LINK is ...
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In multi-o/p isolated converters, would the gating pulses be same for all the outputs and cross regulation happens through transformer turns ratio?

I need to generate 2 outputs , 12V (Output1) and 28V( Output2) from a single isolated flyback converter ( multi- winding). If Iam going for synchronous rectification ( MOSFET is used instead of diode)...
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Will this relay driving circuit work or can it be improved?

I am building an IoT connected ECU for electric 2 wheelers. 3.3v is from an ESP32. Relay Optocoupler Diode I am working on a budget and I am also new to designing that's why I want to know if this ...
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Choose optocoupler diode current limiting resistor

I've designed following circuit: But let's completely forget the MOSFET and only focus on the optocoupler. The signal provided to the input of the optocoupler (yellow) has following characteristics: ...
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Help identifying a SMPS chip

I have an IC from ST marked as: 258 ST GZ151 I can not find any info about this IC. It seems to be the driver for the voltage optocoupler. PS model is FSP-150RAB and it has also an L6599 and NCP1605 ...
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How to guarantee clearance/creepage on mains side of an optocoupler used for 230VAC zero-crossing detection?

Update: Added a diode to protect optocoupler LED As stated in several safety standards (UL 60950 or UL 60750 for example,) we have to guarantee a minimum clearance/creepage between signals of opposite ...
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Opto-isolator voltage

simulate this circuit – Schematic created using CircuitLab The opto isolator emitter has a constant -3.2 V . The opto isolator collector is pulled down by 512 marked resistor. When the opto ...
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Using bidirectional optocoupler instead of two identical optocoupler

I have two types of PNP & NPN proximity sensors and intend to use one connection socket for both types. I design a circuit with two normal optos for each line however to save the parts and space I ...
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Circuit for 12V relay with an optocoupler using 3V3 GPIO

I am trying to design a circuit to control a G6S-2 12V relay that powers on/off a 12V device using a GPIO from an ESP32-WROVER and one PC817 optocoupler. This is the circuit that I have come up after ...
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(Update)Using a bidirectional optocoupler for attaching any PNP & NPN sensor type [duplicate]

I have two different 12 V PNP & NPN proximity sensors. My first design was for each sensor type, having an identical PCB design with a normal optocoupler with a dedicated wiring arrangement. My ...
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Opto coupler output current

I am trying to drive R570412030 SPDT switch using opto-coupler LTV206. I am attaching the setup as shown below: When ever the 3.3 V (control signal) triggers the opto-coupler, the SPDT will be turned ...
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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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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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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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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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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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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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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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