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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In the given circuit of a regulated power supply, why is error computed twice, i.e., before and after isolation?

Circuit Operation \$R_4\$ and \$R_5\$ constitute the potential divider which is fed to the error amplifier \$A_1\$. The reference voltage is generated by the Zener diode \$Z_1\$. The error signal is ...
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94 views

Optoisolator with Logic Output - How To Use IC Circuit Example?

I'm looking at an Optoisolator with a Logic Output..It's an optoisolator with a Schmitt Trigger on the output. I think the datasheet is a little bare for my comfort level, so I'm looking for some ...
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2answers
92 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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34 views

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 ...
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76 views

Opto-characteristic for schematic

I am referring below circuit, where I am using P781 opto-isolator. H1G is I/O pin from LPC2138 controller.( VCC for LPC is 3.3V ) J24: 12V,6W Heater Link for opto datasheet: ...
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35 views

Calculating the resistances of an optoisolator

How to calculate the resistance values of an optocoupler?? The optocoupler used is SFH6156-3. The output collector is being connectd to a 5V supply.A pulldown resistor is also connected to the ...
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33 views

Optocoupler Rf calculation

I am using FODM124 optocoupler. And I want to work in Saturation mode. How to choose VF,IF,CTR and how to calculate Rf?? Bcoz i am seeing different IF's in the datasheet for different Vce's? What ...
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66 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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4k views

Opto-Isolator For Volume Control?

I'm doing an Arduino based project using the PWM hooked up to a 0.5W 8Ω speaker in order to make various sounds, I want to implement a digital volume control and I thought about using another PWM ...
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79 views

When to use or not an optocoupler

I understand the benefits of optocouplers. Always when I'm designing a microcontrolled motor control I isolate the mains from the MCU with those devices. On a few designs I did without the optical ...
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161 views

How to use LM56 to switch on/off a 2kW heater

I have an oil heater at 220V/2000W so lets say 10A. I was thinking of creating a circuit to switch the oil heater on/off with a LM56 (http://www.ti.com/product/lm56). Is it possible using a relay or ...
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37 views

Opto-Coupler that will switch on a 230 volt appliance plugged into the mains [closed]

I am making a little project on my raspberry pi that will act as a simple thermostat, I have managed to work out I need an Opto-coupler but I am not sure it will be able to cope with thr UK's 240 volt ...
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2answers
428 views

Need an optocoupler for getting directly proportional output galvanically isolated from the DC input

I want to use an optocoupler to linearly step down a DC voltage which willy vary from 0V to 400V. That is, I want the output to be directly proportional to the input and I want it to be galvanically ...
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1answer
79 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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108 views

LM358 Op amp problem

simulate this circuit – Schematic created using CircuitLab simulate this circuit Right now my configuration of my circuit is this: http://i.imgur.com/2x5nGcf.jpg The only ...
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42 views

Calculating resistor values for RPi circuit detecting AC current using H11AA1 and PNP transistor

I've got an electronic doorbell system (Aiphone IE-1AD) that sends a ~15Vac signal when the button is pushed. I used this blog post on detecting a signal on a similar door bell using a moteino ...
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62 views

Voltage drop problem?

I made a circuit using PC817 optocoupler. On its 1st pin, i gave 3.3v, 2nd pin was ground. 3rd pin was 12v and on 4th pin i used a pull down resistor with resistor ...
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86 views

Difficulties with using LM358 Op-amp

Basically (Although I'm using an LM358 op amp): Is what I'm trying to design, if I change the current source from the 48uA to 8uA the output on the simulation changes but the output does not in ...
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135 views

Will this schematic work?

Newbie here, trying to learn electronics (Iam from SW background). Looking for someone to review the initial schematic and advise. Haven't ordered the parts yet, so appreciate any tips in finalising ...
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4k views

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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86 views

Low Pass Filter For Square Wave Through An Optoisolator

I've got a higher voltage square wave input that I'm feeding through FOD817B Optoisolator. The square wave frequency is in the range of 30 to 300 Hz. The Circuit is like this: simulate this ...
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20 views

ACPL217 minimum forward voltage

my question is about the ACPL-217 Optocoupler, i use it to control P MOSFET transistor. The ACPL-217 work with the following schema: I want to leave the pin 1 anode of the diode not connected in my ...
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50 views

opto-coupler ON/OFF threshold levels

It is possible to set Vin(off) voltage for optocoupler. There is explained here: TLP280-4 Optocoupler on 12/24V inputs And in the appnote for TLP290 opto-coupler ...
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4answers
142 views

How to get 3.3 output voltage in PC817 opto coupler?

I am using PC817 opto coupler. I want a 3.3 output voltage. In its 1st pin I am giving 12volt and 2nd pin is gnd. I have connected a pull down resistor on 3rd ...
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108 views

Optoisolator with EL wire won't turn off, TRIAC works fine. Why?

I'm pretty new to electronics, and I'm making a circuit to control EL wire with a DC logic control signal. Specifically, I would like to blink the EL wire with the output of a 555 timer. My first ...
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98 views

Why use Optcoupler + Mosfet?

I saw this project: http://diyhacking.com/arduino-lamp-dimmer/ which I'm interessted to(except that I will have to use some 24V, still enough to hurt the Raspberry Pi). There is several things that ...
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3answers
136 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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50 views

How Can i Protect my Oscilloscope from high voltages?

I made an oscilloscope with AT90USB series(activated ADC in micro and send data to my own program in PC via USB).I dont need more than 0-5v but you can never tell.I know I can mislead higher voltages ...
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29 views

issue with optocoupler design for controlling 24volt pulses [duplicate]

to convert 24v pulses varying in frequency. max frequency 5khz. what optocoupler should i use to connect to microcontroller operating at 5volts. will a voltage divider be better in this case.> ...
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55 views

24volt to 5volt pulse conversion without affecting frequency

im a newbie . id really appreciate if you could help me out on this issue. i have a 24v operated pulse generator that i want fed into the arduino working at 5v. how do i change the voltage level ...
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59 views

16 channels relay control with 3.3v pins

I'm going to buy two 16 channels relay boards from Sainsmart : http://www.sainsmart.com/16-channel-12v-relay-module-for-pic-arm-avr-dsp-arduino-msp430-ttl-logic.html I want to control it with a ...
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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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103 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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30 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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1answer
251 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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60 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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78 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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78 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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6k 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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123 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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73 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
172 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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2answers
88 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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45 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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64 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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104 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
53 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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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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57 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 ...