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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Why are relays so frequently driven by optocouplers?
Since the advent of the many microcontroller development boards, like Arduino, there have been a number of relay modules sold to drive mains AC loads.
A lot of these seem to use an optocoupler, ...
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What is "Arduino Optocoupler Disease"?
Another post on this site, when critiquing a pcb design, referred to "Arduino optocoupler disease" spreading across the internet. What type of design mistake does this refer to?
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Optocoupler with phototransistor base lead
I'm thinking about using 4N25 optocoupler - it has a separate lead for base of phototransistor. How do I use it? I suppose I can't leave it floating?
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Criteria behind selecting pwm frequency for speed control of a dc motor?
I'm working on a speed control circuit for a brushed dc motor (24v, 500rpm, 2A, 4kgcm).
The main components that I plan to use are PIC16f873, 4n25 optocoupler, IRFZ44N MOSFET, BY 500 - 800 diode(for ...
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How to drive a MOSFET with an optocoupler?
What's the proper schematic for driving this IRL520NPbF MOSFET from a microcontroller pin through this CNY17F or this SFH6206 optocoupler?
The MOSFET will drive a motor @ 24V, 6A.
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How do I select the accompanying components for an optocoupler?
I'm using an optocoupler (MOC3021) to sense the On/Off state of an electrial appliance using a microcontroller ATmega16L. How do i go about doing this? My mains supply specs are 230V, 50Hz. How do I ...
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Optocoupler input protection
I have to provide some isolated inputs that accept 12-24V. There should be some protection against reverse polarization, transient over-voltage and permanent over voltage (up to 40V) to some degree.
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Why does this optocoupler's datasheet recommend splitting a current limiting resistor in two?
And not only that, they also want to keep a ratio of R1/R2=1.5
The opto in question is ACPL-M21L by Broadcom
Here's a link to the datasheet:
https://docs.broadcom.com/docs/AV02-3462EN
Thanks.
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Optotriac+triac: how do I calculate the gate resistor
I am building a small circuit to turn on/off a 200W heater. I am using a MOC3023 and a BT136. At the datasheet of the the ...
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High side mosfet 12V switch from isolated 3V3 GPIO
I want to switch power of 12V laser sensor from 3V3 STM32H753VI GPIO. I will power on or off for long time (It's not PWM here) I am not comfortable with Mosfet and Optocoupler so I need help to be ...
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opto isolated arduino input
I want to protect a pin with an opto isolator to get an external signal from an electrical meter (35VDC max, 50mA max, 240ms pulse width). The purpose is to count the pulses.
Do you have some ...
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Difference between Zero-Crossing Optoisolator and Regular Optoisolator
I am trying to find any documentation on what the purpose is of a Zero-Crossing Circuit TRIAC Optoisolator. The datasheets don't explain the concept well enough. If you do answer, please include ...
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Optoisolate 2MHz SPI communication
I need to isolate the SPI communication between two chips.
The bottleneck of the communication is on the slave, which apparently can handle up to 2MHz SPI clock ...
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Difference between optoisolator(optocoupler) and solid state relay?
I have been looking into relays and optoisolators. I am aware that there are different optoisolators, with some having a transistor on the detector side which allows current to flow in one direction ...
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Under what conditions does an optocoupler work fastest?
I want to use the optocoupler FODM452R2 in my design. I want this optocoupler to run as fast as it can (i.e.; work with minimum propagation delay and least rise/fall times). What is the optimum R1, R2 ...
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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 among ...
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Digital Dimmer With Microcontroller
I want to build a digital dimmer for resistive Loads.
I have found this circuit for that:
The input voltage is 220VAC 50Hz.
The red box in the picture is for ...
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Using an Opto-Isolator to change an Op-Amp's Amplification
Consider this circuit, which is a standard non-inverting amplifier with an amplification of A = 1+R1/R2.
I now want to be able to change this amplification value ...
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MIDI IN : many circuits
I'm building a MIDI IN to serial port RX cicruit (for Raspberry Pi, or Arduino, or anything else...) using a 6N138 optoisolator.
But I find many different circuits, I don't know why there are so ...
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Validate Triac circuit
I'm designing a device to switch a heating device driven by mains power. I've done quite a lot of research and realize there's a lot of information out there but as i'm dealing with potentially deadly ...
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TRIAC dimmer, circuit design help (resistive load)
Okay guys, I've been tasked with making a light-dimming control system for a 240V heat lamp dissipating around 250W. I need to adjust the heat output on the lamp by control from a microprocessor.
I'm ...
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Why Snub an Optoisolator?
I am using an optocoupler and a power triac to switch 120VAC supply to an ~108 watt fan. The datasheet for my optocoupler requires me to snub the optocoupler output when I'm switching an inductive ...
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Buffering a Digital Microcontroller Signal for Connecting to an Optocoupler
I frequently work on projects in which I use optocouplers for isolating digital +5VDC control signals (for example, from a microcontroller) from the rest of the circuit. However, since these work by ...
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Analog isolation vs Digital Isolation
I am designing an ADC front-end circuit that will accept a 230 Vrms mains connection. My goal is to measure the RMS voltage of the mains.
Though not really necessary, I think it would make sense to ...
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How is this 5-24V input circuit working?
Since I require some kind of wide range input (going to a microcontroller) for a new project, I looked through some designs that are already in use (or were considered at some point) for other ...
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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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When should I fire the TRIAC's gate when controlling an inductive load (AC motor)?
I'm using a combination of opto-triac + TRIAC to control a 230V AC motor with a microcontroller. For detecting the zero-crossing of the voltage I'm using another optocoupler.
I know that the AC motor ...
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Can LEDs or optocouplers be used without a resistor if PWM is used?
LEDs are often connected through a resistor and the purpose of this seems to be to lower the voltage across the LED to around 1.8V. Can PWM be used to lower the voltage instead of a resistor? If so, ...
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Can I stack optocouplers in series to make a higher specification part?
Yet again I'm working with the sub-set parts the PCB assembler house has pre-loaded, and not what is commercially available. Like using 3-6 resistors in place of 1, and more relevant to this question; ...
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What is the purpose of this transistor pair on the front of the optocoupler?
I'm trying to understand the function of the transistors on the input to this optocoupler. Is this a standard/common transistor configuration (that has a name)? I'm having trouble finding a match in ...
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Does a general purpose optocoupler such as CNY17-4 support clean 25 kHz PWM?
I've "scanned" through all possible combinations of values for the current-limiting resistor for the LED input of the CNY17-4 optocoupler, as well as the output pull-up. At 25 kHz, I couldn'...
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Why are optoisolators white?
I've noticed that most of the opto-isolators (optocouplers, opto-triacs) have a white package. Why is that?
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How do I choose my optocoupler to drive a solenoid with a MOSFET?
I need to drive a solenoid with a MOSFET. The solenoid is an 8W solenoid and it will be connected to a +12V voltage.
And this drive command have to be isolated with an optocoupler but I don't know ...
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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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Shift Register output to Relays
sorry for the length.
This is a continuation of my recent question. I have an optocoupled 8-relay board that I’m trying to connect to my microcontroller. I have placed a 74HC595 shift register inline ...
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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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How to sense 24V AC (Thermostat) with a 5V Microcontroller
I'd like to detect thermostat events (heat, fan, ac etc) with an Arduino. I've done quite a bit of investigation but haven't found a definitive solution. Most projects I see involve controlling the ...
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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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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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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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Isolating motor control signals from microcontroller from high voltage/current lines
We need to design an integrated DC motor controller/driver, which will be under microprocessor control. Due to space requirements, either the digital and analog circuitry will be on a single PCB (...
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driving a relay with transistor and Opto-isolator
I am very new in electronics. I am controlling a relay with stm32 micro controller. For the isolation I have used a 4N33 opto-isolator. As my relay coil needs around 250 mA, I used a mps222 ...
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Opto-coupled RS-232 receive circuit
I am looking into a implementing a low-cost RS-232/422 opto-coupled receive circuit. The aim is surge protection and tolerance to DC offsets.
The challenge is that the inputs should be completely ...
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Optocoupler high side vs low side switch
I have a NPN Darlington Optocoupler that I have been using for low side switching. I was wondering if it would be okay to also use as a high side switch?
Optocoupler Datasheet
simulate this circuit &...
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unclean signal at the output of an optocoupler
I use a FOD260L optocoupler and here is its datasheet and diagram below
pin 2 is connected to an atmega168a (supplied by 3.3V ) via 270 ohm resistor. pin 3 is connected to ground of the MCU. On the ...
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Arduino Uno with 12V pump: transistor or optocoupler+12V relay?
I'm not a real expert in electronics but I'm going to start a new project that has completely captured me.
I need to drive a 12V pump with my Arduino Uno. The pump is "Dp0102" (12V, 0.7A). To power ...
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Using the VO2223A to switch a 230Vac LED lamp
I'm looking for something that can switch on and off a 230 Vac, 26mA LED lamp, under microcontroller control. Would a VO2223A, driven by (say) a PIC or Arduino, work as a low-current SSR? The load ...
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No current through AC optocoupler
I am just testing this component MOC3021 optoisolator, its datasheet can be found here.
This is my circuit in Proteus:
Please forgive me for my ignorance of electronics, I have my background in ...
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Interfacing a button to a microcontroller (and PC) with a 50 m long cable
I am designing a board that will be plugged into a computer and will read the status of a button ~50 m away in an office environment (it's actually a lot closer, but the cable is long).
I think ...
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