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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67 views

Opto-isolation amplifier output is too off

(As a follow-up to an earlier question answered by the community - thanks!) So I've got the test circuit setup using the HCPL 7520 (datasheet) now and planning to use an Arduino Uno to measure the ...
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52 views

Opto-isolation amplifier giving no output

First of all, thanks to the community for having such helpful answers here - don't post very often but here's one I could really do some help with. I want to measure a voltage range of 0-100V DC in an ...
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21 views

Reading isolated multichannel input with voltage drop on all channels

I am building a circuit to read atleast 22 input channels (24 vdc) using an Arduino board which essentially works on 3.3 vdc or 5 vdc. My current setup makes use of 22 PC817 optocoupler. I am sharing ...
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20 views

What's the reason for keeping a base line in optocoupler? [duplicate]

Image Source: https://www.vishay.com/docs/83725/4n25.pdf The pin no 6 of the optocoupler IC is connected to the base of the NPN transistor. Should I keep it open? Or grounded? Does it anything to do ...
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17 views

characterize internal capacitor of optocoupler

I am reading article Using an automated Excel® spreadsheet to compensate a flyback converter operated in current-mode by Christophe Basso, Tomas Petrek/David Sabatié. In page 12, they explained how we ...
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27 views

NO current passes through the Opto-coupler in Proteus

I tried to run the AC circuit using Opto-isolator MOC3021 . But no current passes through it. These are the warning in Proteus simulation log Pin 'MT1' does not exist in child module. [U2] Pin 'MT1' ...
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30 views

Read 24 Vac signal with a Raspberry Pi

I want to read a 24 Vac signal coming from my old automatic gate with my Raspberry Pi. The signal tells me if the gate is OPEN->24 Vac or CLOSED->0 Vac. Raspberry Pi input are 3.3 Vdc tollerant. ...
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62 views

Using multiple 4N25 optocouplers - Approach for compact PCB design?

I'm working on building an Ardunio Nano device that detects if automotive 12V circuits are on / off. I was able to successfully build & test a sample circuit provided Phil Frost. The question I ...
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30 views

Is it necessary to remove ground on all layers when using isolated DIO

So, I am using uptocouplers and digital isolators for a project connected to a microcontroller GPIO. I removed the ground (ground plane cutouts) under the load side of the components, is it necessary ...
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27 views

How to extend optocoupler's common mode transient immunity to its Input constant current driver

Hello planning to use an optocoupler to interface a button meters away from the circuit. The optocoupler ILx series already comes with Common Mode Transient Immunity which would work great for my ...
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37 views

TRIAC not triggering

I am attempting to make a circuit that would allow me to control a standard CFL 13W lamp with a microcontroller. As the lamp would run on AC power, I am making use of the following circuit using a ...
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81 views

High or low side switching where the switch (button) is meters away from the circuit

I am making a circuit for a button to be far away from the circuit, about 50 meters round-trip. I have went decided to use an optocoupler to protect the uP from the worst of the outside environment ...
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1k views

Choosing series resistor for Optocoupler LED

How do you choose the series resistor value for the LED side of an optocoupler. My application uses this opto to interface a button that is about 25meters(50 meter wire roundtrip) away from the device....
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42 views

TRIAC driver circuit behavior when switching low current loads

I'm doing a project that involves switching different kinds of loads (edit: by that I mean loads that go from just a couple mA, up to 5A or so) using the usual TRIAC + opto-isolator combo (in my case, ...
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39 views

Sensing doorbell directly off the secondary of the bell transformer, with an ESP

New here, and not so skilled, so be kind to me... I've got a very simple electric, old fashioned "ding-dong" doorbell, that I'd like to migrate to the 21st century. It's basically a ...
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44 views

MOC3043 possible failure

Problem : BTA16 triac is always on with using MOC3043 as driver Facts: BTA16 working correct when moc3043 is disconnected from it's gate pin. Atmega8 output pin is connected to 330ohm resistor and it'...
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61 views

how to generate 70V AC from TLP222G-2

I have 70VDC 30mA source I need to control optoisolators to generate 70V AC signal I can use TLP222g-2 dual isolators. to build the h bridge I have a single PWM channel from my MCU. Is it possible to ...
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49 views

How to use an optocoupler with a transistor on both sides?

I am trying to switch a 17VDC 30mA load with a Raspberry Pi. To provide electrical isolation, I am using a two channel optocoupler, a TLP621-2 (datasheet). The second channel is currently unconnected. ...
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48 views

Zero crossing circuit

I have made a simlpe zero crossing circuit to control the speef of a single phase AC fan through conduction angle control with a Triac. The circuit looks like this with the use of 4n25, an optocoupler:...
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1answer
98 views

Design a 100 watt inverter, but why when the circuit is connected to the power supply sparks out?

I'm making an inverter with 100 Watt power, 220 volt output voltage. The input voltage source of the inverter is from solar panels with a maximum voltage of 18 volts and a maximum current of 5.56 ...
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5answers
3k views

What kind of circuit do I need with a 6N138 optocoupler to get proportional output?

I have 0-5V input that I need to isolate and still output ~ 0-5V to an isolated circuit. I purchased some 6N138 optocouplers to do this but I'm not getting a voltage output with a 5V input. There are ...
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43 views

4N33, optocoupler, photodarlington, getting voltage without connecting any supply

We are using 4N33, optically coupled isolator (datasheet link). The circuit is shown below. In the schematic with R3--> 10K, it was not working so we change to 200K ohm, C2 & ZD1 are not ...
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2answers
68 views

Why did this triac driver resistor let the magic smoke out?

I hope the title is acceptable under this website rules but it is exactly what happened. I wired up this circuit that I thought I tested in the past multiple times, but I might have wired up slightly ...
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88 views

Why “substrate” is exposed through a “do not connect” pin at all?

I've were reading through MOC3041 opto-isolated triac when I noticed this part: "Substrate". It's also repeated later on one page down further, but there's no explanation. I guess that might be the ...
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76 views

Observe if terminals on a PCB became connected. Know nothing about the PCB, except it is powered with the same power supply transformer

I have a PCB with terminals I have access to, otherwise it's an unknown. I want to observe with my microcontroller (uC) if they become (dis)connected. The PCB is powered by a 24 VAC transformer, the ...
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82 views

Control 5V relay board with Raspberry PI GPIO

I would like to control one of these 8-relay boards with my RPI GPIOs. Please check the below schematic - it shows the parts involved for one of the 8 relays. JD-VCC is connected to 5V of the RPI, ...
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23 views

Current Transfor Ratio of an opto-coupler

What does mean by the current transfer ratio of an opto-coupler for input side of the diode side of the opto-coupler and for the out put side of the transistor side of the opto-coupler.
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34 views

Why does my input current inverter is high?

I have a problem with input current in my inverter is high. My inverter will use for solar panel and using boost converter to convert dc voltage 12-18 Volt to 24 volt. I'm using P channel mosfet ...
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1answer
61 views

Interface 24V signal from one device to 3.3V signal on another device

I have a device A that sends a signal through an optocoupler, this signal travels through a 7m cable and is used by another device B that has a SN74LVC1G17SingleSchmitt-TriggerBuffer powered by 3.3V, ...
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1answer
101 views

ESP8266 loses wifi connection on switching a load

I am trying to switch a roller shutter belt winder (RADEMACHER RolloTron Basic 1100) with an AI-Thinker ESP8266 ESP-12E module. As software ESPhome is used. Most of the time the ESP8266 loses its wifi ...
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1answer
57 views

Op Amp for DC Voltage Measurement

I'd like to measure 0-800VDC using the ADC of a PIC18F and opto-isolated from the high voltage. Since optocoupler's CTR is variable and non-linear, I'll use the IL300. Checking this application note, ...
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46 views

Need help in zero cross circuit by using op-amp

I worked on zero crossing circuit by using opto-coupler.Circuit is It is working okay.Zero_crossing signal is There is a 2-3 ms of signal loss is happening with 50Hz of AC signal.I don't want more ...
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3k views

Is R2 needed on this circuit?

I am working on a circuit to drive some water pumps. I intend to achieve a double galvanic isolation between the pumps and the CPU to ensure nothing bad will happen to the CPU. Here is my schematic: ...
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2answers
61 views

How do I make an io pin 12v tolerant?

I've seen plenty of 3v3 circuits that are 5v tolerant, but I'm wondering if I can make something that is 12v tolerant. Basically I have a numato 128 gpio expander and there are so many wires that one ...
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2answers
79 views

Optocoupler Reference

I want to use in my project an isolated optocoupler like this one to switch an IGBT. In the following schematic, taken from this Vishay application note there's a "floating supply" in Vcc1 as you can ...
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50 views

HCPL-3700 voltage detector opto influencing DUT due to low input impedance. Pump float and controller

I am trying to monitor the state of a float in a septic tank using the HCPL-3700. The float is connected to two screw terminals on the controller panel. This float is normally-open with 120VAC ...
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1answer
40 views

Optocoupler - Emitter follower for driving an optocoupler

I have some troubles to understand the above circuit : simulate this circuit – Schematic created using CircuitLab The goal is to discharge the capacitor which was previously charged to 20V ...
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100 views

Can I use an optocoupler to switch an analog signal?

I have this setup to select 1 of 4 signals, pass it through a sensor, then output it to its own output line. It must also maintain all the signals at the output at all times, using optocouplers as ...
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1answer
116 views

How to control a Sonoff Basic switch with an Arduino Nano

My goal is to "switch" a Sonoff Basic (board RF R2 Power) from an Arduino Nano (which is connected to a few sensors). Based on this video, I found which pin to use on the Sonoff. After a test, this is ...
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55 views

Understanding a simple opto-isolator circuit

I have this circuit that is part of a schematic that I am trying to read. I have some idea, but I am not sure that I am correct. All I want is to figure out the D0 and D0_3V3 values. For example ...
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54 views

What is the maximum voltage permitted when MOC3061 is “on”?

First, I am not an engineer,im a hobbyist. I recently talked in a forum thread about (off-state output terminal voltage) in optocouplers. A very good analogy was made between this off-state terminal ...
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26 views

Optocupler-Mosfet output for various output

I'm designing a board equipped with a MCU (atmega4809) that need to control different type of industrial graded equipment at 24VDC. These will be mainly a relay or a solenoid coil for pneumatic valve. ...
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30 views

Is this Opto-coupler + MOSFET + Relay schematic correct for my application?

I have an ESP32, with a floating voltage supply with 3.3V. I want to use it's GPIO to turn on/off a solenoid valve that works at 12V and draws a current of about 2A. I figured that a proper way of ...
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62 views

interfacing MOC3021 with high current back to back scr

I want to drive two back to back thyristor with moc3021 for soft starter.Here is the circuit: This circuit works for medium power SCR such as BT152,But I want to drive a couple of disk thyristor that ...
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34 views

Alternatives to MID400

I'm trying to detect when 24vac is flowing between the "R" and "Y" terminals on my central air conditioner's thermostat using an Arduino Mega2560. I know from the answers to earlier questions posted ...
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1answer
54 views

Passing through/blocking a high voltage dual polarity signal

Good day. The question I have is regarding a device the function of which my employer asked not to discuss in too much detail. But I believe the engineering problem itself is general enough and I will ...
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28 views

back to back SCR firing circuit

I am trying to design a 3-phase soft start circuit.Are these two circuits different? My PCB design and RC snubber between anode & cathode is based on the second one.I want to make sure my circuit ...
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1answer
117 views

How to properly use the 4N25 Optocoupler

I am using a 4N25 (datasheet) in my project and just had a few questions about it. First what I do not understand is that pin 6 is a base pin, but whenever I look up a tutorial for how to use it ...
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20 views

Voltage spikes on output of zero crossing triac optocoupler

I have one connection of the output of the coupler connected to the gate of a triac. The other connection is to one side of the triac. This side of the triac is also connected to a 77 ohm load. At the ...
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33 views

Sharp PC401 Optoisolator Failure

I have a trusty 2005 Edirol UA-20 midi interface, on which MIDI in has recently stopped working. After a bit of testing it appears the Sharp PC401 optoisolator / optocoupler appears to have failed. It ...

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