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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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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2answers
84 views

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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1answer
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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169 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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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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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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3answers
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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5k views

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 optotriac, this circuit is recommended: My question is how is the 180Ohm ...
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3answers
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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1answer
38 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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2answers
111 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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1answer
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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2answers
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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1answer
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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2answers
1k views

MOC3010 & BT136 with Arduino as trigger to power AC light

I've spend days debugging this circuit and have exhausted all possible solutions. I'm trying to use an Arduino PWM pin to light a 120V AC lightbulb. In order to do this I'm using a MOC3010 ...
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1answer
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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46 views

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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55 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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202 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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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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1answer
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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2answers
60 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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1answer
74 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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4answers
6k views

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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2answers
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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154 views

How are the values for the resistances and capacitor chosen in the circuit below

In the circuit shown, the optocopuler is used as a solid state relay and the triac acts as a switch. i would like to know how the resistor values and capacitor value was chosen.
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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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2answers
4k views

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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1answer
6k views

Choosing components for a triac's snubber

I'm interfacing the BT139-600 TRIAC with this MOC3051-M Opto-triac. I want to build a snubber circuit for the TRIAC as shown in the MOC3051M opto-triac's datasheet @ page 8, figure 12. The load ...
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2answers
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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1answer
103 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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1answer
122 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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88 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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3answers
136 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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3answers
244 views

Is this use of optocoupler wrong?

This is nearly not exactly how the circuit looks like, but I have a feeling that this circuit could cause problems while working. My feeling is that initially as Q1 would be in ON position, the ...
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5answers
760 views

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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87 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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1answer
245 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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2answers
202 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 ...