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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When should I use opto-isolators and isloated DC-DC converters?

I am using multiple DC-DC converters to obtain 12V and 5V. Shall I use non-isolated or isolated converter for Arduino's? From what I have read so far, isolated are used when you have inductive ...
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29 views

SSR selection - how is on resistance related to output IV curve?

I am looking at the datasheet at the link below, and I can't for the life of me figure out what I am missing. http://www.digikey.ca/product-detail/en/TLP3542(F)/TLP3542F-ND/871299 This is a Toshiba ...
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36 views

Difficulty understanding data over opto-diac

I'm having difficulty understanding the data over MOC3021, DIAC side. Should I see it as with DB3? So DB3's \$V_{bo}\$ (28-36V) is the same in opto-diac, and DB3's \$V_o\$ (min 5V) is the same as ...
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50 views

Converting a Low Side Driver to a High Side Driver

I've run into an issue with a product integration we are performing in which we are taking a device whose I/O is meant to accept high side digital inputs (+24VDC) but needs to be driven by another ...
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51 views

Pull-up or pull-down at the optocoupler output

For a normal optocoupler with a LED and a phototransistor, we can put the load resistor (RL) at the emitter or the collector of the phototransistor, just like this But for a high-speed optocoupler ...
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38 views

Use high-speed optocoupler with slow input signal

As known, a slow input is usually not good for CMOS digital circuit design. I wonder, if the high-speed optocouplers such as 6N137, HCPL-060L, etc, can be used with slow input signals, such as to ...
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63 views

reverse function optocoupler

Ok, I know the basic function of an optocoupler is "turn on irLED, triggering a phototransistor and allowing current to flow"; an optical off then on switch. Is there a reverse optocoupler, i.e. ...
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36 views

Question regarding a resistor in optocoupler/TRIAC circuit

I'm building a ac motor starter with a optocoupler (FOD4218) and a TRIAC (BTA16), one for each phase in a three phase 400V system. I have a question regarding the circuits that can be found all over ...
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96 views

Designing an ethernet isolator

I'm trying to galvanically isolate a device which is controlled by ethernet (1000base t) via computer. I've been looking and apparently the ethernet standard provides some isolation, but after I ...
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110 views

MIDI to Arduino with a 4N38 Optocoupler

I ordered a set of optocouplers the other day and was excited when they finally came in. Unfortunately, I've having a bit of trouble getting them to work. Simple on/off tasks work fine but when I ...
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39 views

Triac - opto-coupler Circuit Confusion

I have the following question regarding this circuit: How is the opto being used to trigger the base of the triac?The collector of the photo-transistor is connected to the base of the triac. As per ...
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78 views

555 as a Digital Coupler

I want to read MIDI data with an arduino (specifically an ATtiny85) for use in a synthesizer. The only method I'm aware of involves using an optocoupler such as the 6N138 found on this Instructable. ...
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32 views

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 ...
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46 views

Driving the floating power MOSFETs

In a battery balancing system, I have four transistors and some of them are floating as you can see in this circuit: There are four battery packs each made of two batteries (Li-Ion) and charged via ...
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71 views

Opto-coupler base connection speed influence

I am using a 4N25 opto-coupler for 5kHz to 10kHz application. In some datasheets the turn on and turn off times are mentioned to be 3us. I am wondering if this opto-coupler is suitable for my ...
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49 views

Is it safe to use optoisolator for a longer period? [duplicate]

I have the following optoisolator  PC817. It is a 4-Pin Phototransistor Optoisolator. My idea is basically to control electrical appliances in my home. The power supply in my country is 230V 50Hz. ...
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52 views

Why do fiber-optic interfaces have much higher bandwidth than optocouplers?

I've noticed that optocouplers typically have a bandwidth in the kHz range (i.e 200 kHz). Fiber-optic interfaces can reach speeds of 100 gigabits / sec. What's so different about these two ...
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46 views

Opto interface with LPC controller

I am using heater circuit for bio-medical application ( to achieve 37 degree Celsius for blood samples ). I am using opto-isolator P781F to isolate control circuit ( Micro-controller I/O pins - H1G ...
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Driving an optoisolator with a 2N2222?

I'm driving an opto-isolated MOSFET gate driver with a 2n2222 transistor from a 3.3V microcontroller (TI Tiva C, 2-8mA max per pin). The IX3108G that I selected needs 10-16mA to be driven ON. This ...
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54 views

Ground trigger on relay

I have been doing this for years (on automotive projects) but the need finally arose to clarify: When using a SPDT 12V relay (with internal flyback diode), should I isolate the ground trigger when ...
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63 views

How long will it take to kill a MOSFET with heat?

Example; http://www.aosmd.com/res/data_sheets/AOK42S60.pdf With this; http://www.irf.com/product-info/datasheets/data/pvin.pdf As I was taught in another question, the 40nC gate charge being hit ...
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80 views

Does a MOSFET need current to operate without switching on and off fast?

I know MOSFETs need to have a bootstrap circuit for N-channel on the high side of, say, an H-bridge; but if you're running AOK42S60L with this (as a general on-off switch, not as a fast switched ...
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201 views

isolated input circuit to check regular switch or photo-transistor

I am trying to develop a circuit that is compatible with a regular switch (push, reed, other) and also a phototransistor. The application is pinball, where there are any number of switches and IR ...
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59 views

How to add the two output of a PWM IC?

I need to sum output A and output B of a PWM (UC3526AN) because each output have a maximum duty cycle of 0.45. I try with 2 diode and a limiting resistor(R1) for the led inside the optocoupler ...
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73 views

Optocoupler drives a transistor - optocoupler doesn't turn off

This is the circuit which comes from Microchip DALI example app note http://ww1.microchip.com/downloads/en/AppNotes/01465A.pdf Here's the deal. Everything works as expected, if this circuit is ...
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52 views

opto-isolator 6N137 output not toggling

I am using 6N137 opto-isolator for my circuit. I have attached schematic for the same. I am giving Input and Enable from SMPS as shown and ground is same. VCC and EN is 3.3V from SMPS. But while ...
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168 views

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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49 views

closing a circuit programatically if ground can't be interrupted

I need to be able to "push" a button on a control panel using python and an arduino board. My problem here is that the button in question, when depressed, sends 16 vdc to an outgoing wire that ...
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3answers
103 views

Switching polarity of rectified AC power with a microcontroller

I am trying to create a circuit that will allow me to control the polarity of the current flowing through a coil in order to attract or repel a magnet. I would like to use two MOSFETs in series since ...
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100 views

Is this the behavior of a broken mosfet?

I designed this circuit to switch on/off 8 solenoid valves for a programmable dancing fountain that I am building. The GPIO is coming from a Raspberry Pi. VCC is coming from a 12V deep cycle car ...
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45 views

Replace photodiode by optocoupler

My audio receiver which has a room-to-room interface. This is basically an input where a photodiode gets plugged into that can be placed in a different room that the user doesn't have a visual ...
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102 views

Why do they put some optocouplers in 6-pin packages?

Example: It is obvious that an optocoupler which provides a pin for the base of the internal transistor (e.g.; PS2621) cannot be in a 4-pin device. My question is not about this kind of ...
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117 views

Why do we prefer zero-crossing optotriacs for driving triacs?

I usually see a special type of optotriac which has internal zero-crossing detection circuit in it. This type of optotriac is generally used for driving triacs. But, I don't understand its necessity. ...
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87 views

6N137 Isolating Ground

I am trying to control speed of a DC motor using PWM. To reduce coupling of motor noise onto my electronics, I am using a separate power supply for both(LED and Phototransistor) and am planning to ...
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135 views

220VAC to TTL converter

I'm building a circuit that sends TTL level signal to uP whether AC signal exists or not. The schematic is as follows: Actually, the circuit almost works as I expect; however, there occurs some ...
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45 views

Sense continuity in cable and lock with MCU

I'm building a "smart" cable lock system where the user will put a steel fitting attached to the end of a steel cable into a lock aperture, after which the presence of the steel fitting needs to be ...
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1answer
86 views

Need to choose between 48 solenoids, trying to design a proper circuit to do so

I am in the process of designing a project that will allow a Raspberry Pi to "print" to an old (60s) electric typewriter. I have decided to have a push-solenoid for each key (24V), for 48 total keys. ...
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136 views

Wired vs SMD resistor on 230V optocoupler input

For circuits similar to the one below, we used large wire resistors with proper power rating in our past designs. The question came up, if it would be a good idea to replace the resistor with SMD ...
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243 views

Circuit for supporting, common anode AND cathode RGB LED Matrices

I'm designing a driver / controller board for 8x8 RGB LED Matrices that then can be daisy chained to e.g. make an 16x64 Matrix or so. So I came up with a couple of designs that I've tested and so ...
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201 views

arduino: turn on-off a 12V cpu fan with optocoupler

I wish to use a simple way to turn on-off a 4 wire cpu fan using a digital output of the Arduino board. Since even with PWM=0 the fan works at 30% of the full speed, i have to find a way to cut off ...
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46 views

What are the main differences between 4n25 and SFH6156-2T optocouplers?

I'm looking for a 4 pin surface mount equivalent to a 4n25 optocoupler. I'm really not sure what to look for when comparing the data sheets of each optocoupler and I want to try avoid purchasing the ...
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2answers
92 views

Optoisolator not turning off

I'm using an optoisolator for high side switching a Nixie tube. For some reason, the optoisolator is not fully turning off, allowing the a very minimal amount of current to flow through the Nixie ...
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81 views

Need help on proper circuit connection

I am trying to test IGBT switching using the following circuit but the IGBT smoked out. I am using MSP430 with g2553 chip, NMK0505SAC dc-dc converter, FOD3184 optocoupler and IRG4BC20UD. Please help ...
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166 views

high speed optocoupler circuit

I have 4n35 optocouplers, I am using these to isolate a motor driver circuit and the Arduino controlling it. I put one on the slave select pin and one on the tx line to the motor controller (there is ...
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225 views

How to drive an IGBT with an optocoupler?

What's the proper schematic for driving the IGBT (IRG4BC20UD) from a microcontroller (MSP430-g2553) pin through the optocoupler (FOD3184)? I am going to design a full bridge inverter to drive 9W CFLs ...
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215 views

Will replacing the MOC3024 with MOC3021 make any change

I'm student of 10th grade and new to electronics I'm trying to make a switch to control appliances which runs on AC mains and I don't want to use any relay see the circuit diagram from the link to ...
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136 views

Optocouplers for purposes other than galvanic isolation?

In the diagram below there are two modules, A and B, which are separated by a physical distance of about 15m. Module A has a 12V DC power input. Module A powers module B (they share a common ground). ...
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Using an optocoupler to put an AC signal on a DC bias

Expanding from this question Can an opto-isolated input be analog?: Can you use an optocoupler to take an AC signal and attach it to a DC bias? More specifically, can you take something like a 1V ...
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216 views

Solid state relay (or equivalent/alternative) to drive 6V DC from a 3.3V micro

I have to open/close two wire from a closed device. I cannot open due to it's under warranty, and the only part that I can open and modify is an external button that connects the two wires. Firstly I ...