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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76 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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386 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 ...
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226 views

Trigger input with varying input voltages

Currently I am trying to build a circuit, with the goal of triggering a pin of an ESP8266 from varying input voltages (in the range of 5 to max 15 volts it should get triggered). Also the input should ...
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346 views

How much current does an LED in optocoupler draw?

I am planning to actuate the relay (opto-isolated) using the GPIO pins of Nodemcu. NodeMcu's datasheet says that maximum current that can be drawn out of a GPIO pin is 12 mA. Any load more that may ...
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151 views

Sense 230V - voltage

Brief sum up (you can go directly to the end if you already read the sum up in the other question) For a home project I'm making a controller to drive a two-direction 230V motor. For those unfamiliar ...
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3k views

Detect 220 VAC with a Raspberry Pi

I want to build a simple device to check if the light is on or off. I found some schematics but I need to be sure that it is safe. Source : How to detect 220 VAC voltage using an opto-isolator My ...
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1answer
228 views

Control 24VAC solenoid with arduino using a octocopuler and a Triac

Following a previous question I implemented the following schematic on my PCB. The schematic : My PCB: I have been unable to make it work, if I measure the voltage on j13 it's allways 25v, i know ...
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35 views

High Speed Piezoactuator Driver-Unexpected (Low) Voltage Output

I'm working on a project that requires charging and discharging a piezoactuator (150V, 1.5μF) extremely fast, IE total slew time allowed ~50μs (so somewhere around a 11A pulse). My background is in ...
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37 views

Low Voltage Marx Generator Switch

I have a low voltage Marx generator which is connected to a coil inductor, eventually forming an LC oscillator. I want to find a way to switch the circuit on, but because the voltage is low I cannot ...
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2answers
170 views

Automotive signal isolation - alternatives to optocouplers

I'm working on an automotive project, where I'd like to interface various digital signals to an MCU. The signals can either be ON/OFF (e.g. radiator fans) or measurements of pulse frequency, width, ...
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1answer
621 views

Latching/Non-Latching Relay Driver Circuit with darlington optocoupler

I'm designing a circuit where an ESP8266 controls two types of relays, a single coil latching relay and a normal non-latching relay. The relays are power relays use to control low power electrical ...
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1answer
586 views

4 channel optocoupler [duplicate]

I was designing a dual H bridge board which uses some logic signals to drive 8 mosfets. Initially I was using 8 optocouplers per board which was really annoying to wire up. after a bit of searching, I ...
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2answers
88 views

“Fast” pulse (8µs) low current (10µA - 100µA) amplification for optocouplers

I got this problem where a inverted pulse of 8µs has to be amplified because the pulse only delivers 10-100µA. The signal will be transmitted over a optocoupler and sent to a mc that interrupts upon ...
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3answers
1k views

How does Galvanic isolation work?

I am unable to understand how does galvanic isolation work either via an optocoupler or a transformer. In an optocoupler, the input side current caused LED to emit infra red light which basically ...
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1answer
821 views

Driving a 24VAC solenoid with arduino using a octocopuler and a triac

Following a previous question I have redesigned my schematic: I'm trying to energize a solenoid used to open and close a 24VAC sprinkler valve I have the following questions : 1) The GPIO leg can ...
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1answer
370 views

logic level conversions for opto-isolators in digital input acquisition

This isn't my usual job, I'm not an EE, but I want to give it shot... This question concerns developing an interface board to connect a device (DUT) to a test system in a manufacturing scenario. ...
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167 views

Current loop protection from wrong connection of the wires

I have built a current loop protection circuit based on the topic Using a microcontroller ADC to measure a 4-20mA sensor It works good. The next step is I want to protect the input of the circuit ...
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2answers
128 views

Bidirectional (opto?) isolators for any protocol?

I would like to isolate digital serial communication between 2 circuits. I don't know much about the protocol between two circuits. It is not a common protocol such as SPI or I2C. Shortest pulses are ...
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1answer
279 views

Avoiding turn-off of zero-crossing optotriac

I'm designing a circuit that switches a load using a regular TRIAC (say, a BT-137) being fed by a MOC3063 - an optotriac with zero crossing detection. The circuit being fed by the TRIAC can be either ...
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1answer
167 views

Bypassing DSLR battery to power camera from power supply cheaply with bidirectional optocouplers

I am trying to power my Nikon DSLR with a permanent power source instead of the battery for long captures (overnight) without buying the overpriced battery adapter. I can't simply connect a AC-DC ...
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1answer
582 views

AC Voltage Detector with MID400 optocoupler

The task I am trying to achieve is as follows: I am using a MID400 optocoupler to send either a 5V or 0V signal to a pi plate depending on if there is AC voltage present. I am using 120V AC from a ...
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1answer
102 views

Switch a line level audio signal - which chip is best WRT noise, low loss? [closed]

I am relatively unexperienced with audio circuits, and need to switch a standard line level signal, AC, about 6Vpp. I have the chips listed below, and would very much appreciate some pointers as to ...
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232 views

Induced power supply noise on switch contact

I have a circuit that has a 24V section and a 5V section, separated by opto-isolators and an isolated DCDC converter. Both sides of the DC-DC have decoupling caps, and the MCU has one per Vcc pin. ...
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2answers
262 views

Detect 230VAC or 12VDC in the same pin [closed]

I'm designing an input interface for a microcontroller (uC). Want to detect signals (only want to know if there is voltage or not) of different typology, so you can have in the same input to the board:...
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3answers
615 views

How and what kind of noise can an optoisolator filter?

How does an optocoupler filter noise? As an illustrative example, below three remote sensors are receiving pulses from a single source: In the top scheme there is no optocoupler/optoisolator. In the ...
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97 views

Why is the output voltage of this circuit is changing in simulation?

Circuit 1: Circuit 2: The only difference between Circuit 1 and Circuit 2 is`that in Circuit 2 a parallel 2.2k resistor R8 is added as a load next to R6. Why adding this R8 is halving the output ...
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144 views

Issues with coupling a buffer to an optocoupler

The buffer below between the input and the opto works fine itself, but Im having problem when Im interfacing it with 4n32 on the right. (Frequency of the hardware-trigger will be around 40Hz pulse ...
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1answer
125 views

GPIO pins of CC2650 are capable of driving the opto-coupler(4n35) directly?

I need to drive opto-coupler(4n35) from the GPIO pins of the CC2650 (Pins other than high drive capability). Are the GPIO pins of CC2650 capable of driving the optocoupler directly? Will they ...
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226 views

What is use of R41 (base to emitter) resistor in Transistor Relay Circuit?

I am controlling relay from arduino, using the following circuit. I want to understand what is use of R41 (base to emitter resistor)? Is it required for base termination? How is its value ...
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114 views

Solenoid control with current limiter - is it correct?

last year, I designed a solenoid control board which is still working very well. The board was based on ATmega328p and used an optoisolator 6N136 to isolate the high power from the low power and I ...
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2answers
368 views

pull up or pull down resistor for optocoupler

I tried to make a PWM AC dimmer circuit which found in instructables.com as below: but the 100k 1W resistor got hot. Could using a pull up (or maybe pull down) resistor for optocoupler solve the ...
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121 views

Maximum Trigger Current IFT

When researching optocouplers I often see that the differences between models (like the MOC3020/MOC3021) is the Ift (Maximum Trigger Current). For example the MOC3020 has an Ift of 15mA and the ...
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384 views

Relay or optocoupler to switch thermostat wires

I'm doing a project to replace my thermostat with a DIY one. I'm trying to figure out how to switch the heating/cooling/fan/humidity wires. I'm inclined to go with an optocoupler like the 4N35. It ...
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189 views

Trouble with optocoupler 4n35

I'm trying to ride a full bridge inverter using SPWM to control the MOSFETs, the signal SPWM that I use to control the MOSFETs comes from an NI elvis, but it only provides 5V and I know the fact that ...
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644 views

Current limiting with optocoupler

Update: I've removed all irrelevant information and simplified the question. The OPA548 operational amplifier provides adjustable current limit that can be controlled digitally with a current-out DAC....
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3answers
125 views

Optically-Isolating Limit Switches

I've noticed many motion control cards have optically-isolated inputs for limit switches? I can understand why you may do this with a signal which travels between two systems with separate power ...
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2answers
273 views

Any diode to protect an optocoupler with low voltage drop?

I have this design. By a possible mistake from user, the circuit would receive 12 V AC, and may destroy the optotransistor on reverse voltage cicle. I can put a diode D1 before the resistor, but the ...
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100 views

what will happen if an optocoupler output is connected to AC?

What will happens to the output of an 4n25 if the final user by mistake wires an AC current (12 V . AC)? Will This destroy the transistor? I can't find this condition in datasheets.
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90 views

Is this optocoupler-based circuit design reliable?

Hello, I have designed this optocoupler interface to an stepper driver. However, I'm not sure if it's all right. For R1 I made (5-3.3)/10mA ≈ 180 ohms. 3.3V taking into account the two leds voltage ...
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3answers
462 views

Making my own isolation transformer

If I obtain the iron core from a microwave oven transformer and strip off all the windings then wind 2 coils, each being 20 turns with 12 gauge wire, will I effectively have made an isolation ...
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4answers
1k views

Why we use two photodiodes as optoisolator or optocoupler?

Why do we need two photodiodes in order to create an optoisolator or optocoupler? Many sources say that it is to compensate for the non-linearity of the diodes, but is there any explanation based on ...
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1answer
907 views

Triac moc3041 resistors

I'm trying to understand few things about triacs etc. and I found datasheet for MOC3041 And there're two resistors which purpose I don't really understand. I'm talking about the 330Ohm and 360Ohm ...
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1answer
418 views

Opto-coupled EIA-422 receiver (understanding suggested circuits)

I am looking at a standard for communication of marine electronics (NMEA). The standard is electrically essentially EIA-422 but it prescribes opto-coupled differential receiver pins without connection ...
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3answers
779 views

AC Switching Relay isolation with Optocoupler

I am trying to do a schematic to switch a relay using my MCU. MCU GPIO works at 3.3V. I have come across the following schematic, but unable to calculate proper CTR and thus the value of Base ...
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2answers
558 views

24 VAC Detection Using Optocoupler

I have been using an HCPL3700 to detect 24VAC, but they are large and relatively expensive. I have tested the design shown in the figure (AC input to the diode, and measuring output collector-emitter ...
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1answer
7k views

AC Optocoupler for 230V line detection

I am trying to detect line voltage (230V AC, if the supply is ON/OFF) by a microcontroller with the help of an AC optocoupler. The optocouplers I have evaluated are PC814, H11AA1 and SFH620A-3, out of ...
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2answers
513 views

220 VAC detection using Optocoupler

I tried to detect 220V AC in my microcontroller using SFH620A-3 with series resistance of 440K (2 x 220K, 1/4 watts SMD type), a 1uF at the output to smoothen the pulse and every works as expected. ...
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4answers
8k views

How to convert a digital signal from 5V to 24V?

I have an industrial application where I have to interface a microcontroller output which gives a digital signal (0V to 5V) on its outputs and I want this signal to control a relay which takes (0V to ...
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0answers
180 views

Help identifying this circuit and understanding how it works

So I'm hoping to make a few modifications to my computer case and have found that a number of the LED elements have an associated circuit to them. I want to be able to understand what I'm doing and ...
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1answer
201 views

Question for Linear opto isolator circuit

-I want to have the same potential or linearity in opto isolator's input and output Pic below there is my previous circuit ,sketch and Changed Sketch(the last pic),but it's not linear with PC817. I ...