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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9
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1answer
8k 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 ...
0
votes
1answer
45 views

Connecting a Camera Hot Shoe to a homemade strobe

The Situation simulate this circuit – Schematic created using CircuitLab I need to trigger a strobe from a Sony Hot Shoe. A 3.5mm jack lead comes out of the hot shoe. Using a ...
-1
votes
1answer
106 views

How does this optocoupler work? [closed]

I am working on an embedded system and unfortunately I have not got a proper schematic for checking power failure. However, I have a PCB for that so I drew a schematic based on the PCB. I just ...
0
votes
1answer
47 views

An SPDT switch using TRIACs

I need to design a circuit that implements an SPDT switch using Triacs and Optoisolators. Currently I am implementing this with two pairs of Optoisolated Triacs with one having inverted signal from ...
0
votes
1answer
93 views

Which circuit is more Stable?

The circuits in the picture are basically opto-couplers connected to a relay circuit. The input pin of the opto coupler is connected to a MCU and the output of the opto coupler is connected to the ...
0
votes
1answer
92 views

Arduino 4N35 input

I trying to interface the arduino digital pins through an optoconnector attached to an LED of a consumer electronic device. I have bought the recommended component for this. Before I would even get ...
0
votes
1answer
44 views

isolated high voltage H-bridge

I want to control on isolated H bridge that powered with 100V and can drive up to 0.5A low frequency 3HZ but Pulse width of 200uS . the response times should be is US so i cant use Solid State Relay ...
-1
votes
1answer
62 views

How to choose optocoupler

The circuit below will drive a 12v motor using an optocoupler. In the circuit PC817 is used but how do you know which optocoupler to use?
1
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3answers
59 views

switching 3A/5V with an optocoupler [closed]

I am planning to switch the 5V line to a USB load. I have being going around different suppliers looking for an optocoupler that can handle 3A at 5V. I have seen a few, but upon looking at the ...
1
vote
1answer
51 views

ESP8266 line voltage detection, schmitt trigger needed?

I want to read 230V/50Hz line voltage input signals with an ESP8266. Please have a look at my schematic, I chose an opto-isolator with AC input (LTV-354T) and added a simple RC filter to keep the ...
0
votes
1answer
39 views

Optocoupler calculate resistance on output

How do I calculate the resistance between the Anode and the Cathode of an Optocoupler (while the optocoupler is on). I am messing aroung a little bit with optocouplers and found out using an ...
0
votes
1answer
41 views

Optocoupler 4N25 saturated CTR

I'm studying optocouplers in general, and in special the 4N25. I'm applying the optocoupler in a zero crossing circuit, like this one: I know the CTR is minimum of 20%, but checking the datasheet ...
-1
votes
3answers
95 views

How to detect 220 VAC voltage using an opto-isolator

I created the following circuit. i plugged it in and it works!! Now i thought to add an opto-isolator to the circuit in place of the LED. The value of C was the same. $$ X_c = {(({220volts-1....
3
votes
2answers
84 views

Can anyone give me tips on how to proceed with this triac/optocoupler/motor circuit fix?

I'm working on a Fisher Digital Vortex Mixer that has an intermittent issue in which the AC motor is energized, but no movement occurs. By rough estimate, this will occur on one of every 8 attempts. ...
0
votes
3answers
80 views

Is this a good method to detect 120VAC

I need an embedded micro controller to detect some 120V AC signals, I decided it would be safest and most likely the best to use an opto-isolator. Below is my circuit, I rectify the incoming 120V and ...
0
votes
1answer
46 views

Fluctuating digital input on arduino uno r3 when connected to Photocoupler

I am trying to use a Photocoupler 4N-25 with an arduino uno r3. I connected the collector to +5volts and the emitter to ditital pin 0. Now, since there is no voltage applied to the gate and I haven'...
0
votes
1answer
77 views

h-bridge voltage readings using bipolar junction transistor

I am using the following h-bridge setup using optocouplers, a DC motor and bipolar junction transistors (2N3904 for the NPN and 2N3906 for the PNP) Everything works as expected, but my question has ...
-3
votes
1answer
62 views

SCR drop voltage

unfortunately there is a voltage drop for the SCR , as I used an opto with a single SCR , when I checked the open anode cathode voltage without any load it was about 5V instead of 12 volts, when I add ...
0
votes
2answers
75 views

AC Line detection using MID400

I want to detect an AC Line Voltage (230V RMS, 50 Hz) and interface it with a microcontroller. I am aware about two solutions. Using an optocoupler like PC817 [datasheet] using MID400 [datasheet]....
0
votes
2answers
85 views

Zero Crossing Circuit Input Resistor

I'm building a dimmer, and got some questions about the resistor in the zero cross circuit. My circuit is like the image above, and I'm wondering if in the case of 100V input the current is to ...
0
votes
2answers
70 views

5/12V voltage TTL selector

I want to select an output of 5 or 12 V with an isolated digital output control signal (Vcc 3.3V in the picture, 0 selects 5V, 1 selects 12V). Right now I have something like this: Corrected version:...
0
votes
2answers
52 views

How can I close a remote controller switch with an optocoupler and a Pi?

I'm trying to close the contacts of a remote controller (wires are soldered to either side). I have an RPi and I'm yet to buy an optocoupler. What would I need to get this to work? A Pi outputs 3.3v ...
0
votes
1answer
57 views

Is it safe to use Vcc from processor side or use another supply

I have a Toradex Carrier Board. It has few GPIO pins. I need to use them as inputs. In our application we will give 12v input but as the pins can only take 3.3v so I have to design a simple board ...
1
vote
1answer
108 views

Cheap and small alternative to optoisolators: is there any?

Typical opto has several kV isolation voltage (which is not always needed), has relatively big cases (TLP291 in 4-SOIC is one of the smallest as I know) and typical price up to 1 USD in small amounts (...
0
votes
2answers
65 views

Opto-coupled PWM

Following on from this question: I have the task of setting a voltage V_set using PWM. The challenge arises from the fact, that V_set is referenced to a different ground than the MCU. My currently ...
0
votes
2answers
49 views

Opto-coupled PWM output

I have a circuit with two different ground levels. Using a optocoupler, I want to translate a PWM signal to the new ground level. Does there exist a easier method than the following? (Ideally with ...
2
votes
0answers
39 views

Optocoupler in reverse-active mode

I was recently reminded that BJTs can be used in reverse active mode. Can somebody enlighten me whether and to what extent the same is true for optocouplers? Do the same limitations apply to reverse ...
0
votes
2answers
40 views

Using a IR2125 to drive a MOSFET gate

I've done a good bit of experimentation and learned quite a bit from other members of the site here. I've built several circuits that drive an N-channel MOSFET on the "low side". But to build an H-...
23
votes
5answers
7k 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, ...
1
vote
4answers
69 views

What's the difference in a digital optocoupler and a non digital

I'm looking at 2 different optocouplers.The Avaago ACPL-K44T and the ACPL-227. The ACPL-K43T states that it's a digital opto-coupler while Avago ACPL-227 doesn't. Schematically, they're a bit ...
0
votes
2answers
102 views

SCR which can conduct 230V AC at Zero gate voltage

As per the image, an operation for manual & Auto logic where manual can overwritten auto command and vice versa. The red circled area is an SCR(Silicon Controlled Rectifier). I'm looking for a SCR ...
1
vote
0answers
43 views

FET Default on, Turn off with Optocoupler

I am relatively new to electronics and having trouble designing a circuit for a redundant power supply, which I would like to switch to battery if the voltage regulator turns off. This will be ...
0
votes
1answer
45 views

Triac connected CFL or Incandescent bulb or Electronic ballast tubelight FLASHES

I am building a triac based dimming circuit. Everything is working fine. The problem which I am facing is when I turn on or off any appliance (NOT CONNECTED TO TRIAC) in my any other room, the ...
3
votes
3answers
202 views

Interfacing open-collector optoisolator to 3.3V microcontroller

I have a bit of a puzzle on my hands trying to interface a Fairchild MID400 optoisolator (popular "logic level" optoisolator for mains detection) to a 3.3V GPIO pin. The MID400 is a 5V part [*] and ...
0
votes
2answers
48 views

Am I able to make a comparator on optocoupler?

Initially I'm trying to make over current protection scheme. So if the R2 current (and therefore R2 + D1 voltage) will go higher than some certain level I should have a signal to break the circuit. I'...
0
votes
2answers
101 views

Isolated 1-10V (or 0-10V) output

I need to control an LED driver with analog 0(1)-10V control input. This control device should be very cheap and compact so until now I made a schematic which uses the fact that those drivers have ...
0
votes
2answers
70 views

Is hobby relay adequate for air conditioner automation with microprocessor

I'd like to use a Beaglebone Black(3.3v Logic) plus a 3.3V to 5V logic level shifter(74HC125) to control an opto-isloated Songle Relay that has the following specs: Rated Resistive load: 10A 125VAC;...
0
votes
1answer
30 views

AC Analog Isolation

Please excuse my limited knowledge of electronics, my problem is I've a circuit which is driven by a variable AC signal using LabVIEW it ranges from 100Hz to 100kHz (I can lower this to 30-50kHz if ...
1
vote
1answer
148 views

(schematic) Using a micro controller to drive Opto-coupler > 555 timer > MOSFET

I'm trying to use a micro-controller to activate an opto-coupler connected to 555 timer which is connected to a MOSFET. The circuit will drive a solenoid which draws 2amps at 12v. I'm new to circuit ...
0
votes
1answer
63 views

Which isolated ground should I use for an RF can/shield over an optically-isolating component?

I'm building a PCB that uses an optically-isolated voltage-sensor IC which takes an input voltage of -0.2V to 0.2V on one side and generates an isolated, proportional output that ranges from 0V to ...
0
votes
2answers
120 views

AC/DC optocoupler wiring

Looking for some clarification on the proper wiring of an AC/DC optocoupler (HCPL3700, datasheet) when working with 120vac. From what i read online it looks like a need a resistor on the hot side ...
0
votes
1answer
84 views

It makes sense to use an optocoupler with the same ground?

I've a microcontroller and I want to have some protection for a digital output, but I only have one power source so I was thinking on use a diode to prevent backward currents. It's reasonable to use ...
5
votes
3answers
215 views

Why does this optocoupler circuit work without getting destroyed?

This circuit is being used for mains detection. Input is being fed directly from 220V 50Hz mains and output goes to Arduino which is running on 3.3V. Theoretically the optocoupler LED should burn out ...
0
votes
1answer
30 views

Smps feedback method [closed]

Hello all I have seen some smps use output secondary for feedback using via opto coupler. And in other smpa i have seen they use primary aux winding feedback only. Which one is good to use and easly ...
1
vote
2answers
301 views

Driving a 24V isolated load from a 3.3V MCU

I am looking to drive a 12-24V purely resistive load from a 3.3V MCU. I would like to use an opto-isolator to separate the circuits electrically. I've drawn up the following circuit, but I'm not ...
0
votes
1answer
122 views

Substituting Arduino for ESP8266 in a (Yet Another!) Garage Door Controller

I have a garage door opener with two leads that will activate the motor if the leads are shorted. I hooked my multimeter into the leads and measured ~24VDC and triggered the motor ~50mA. Using an ...
0
votes
1answer
48 views

connect a triac to optoisolator

I want to use a current sense from the CR2550 connected to optoisolator LDA 110 and drive the gate of a triac. How do I connect these two systems with out killing either? Update Thanks for all the ...
-2
votes
1answer
54 views

How to calculate the resistors to convert 24V to 3.3V using a TCMD4000

I would like to convert a 24V signal to a 3.3V signal using a TCMD4000 optocoupler. Datasheet: http://www.vishay.com/docs/83513/tcmd1000.pdf How can I calculate the resistor's value on the input (...