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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optocoupler help

I think I'm having a hard time understanding how an optocoupler works. I made a circuit based on example 15 if the Arduino projects book, but instead of trying to hack a button, I'm trying to just ...
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300 views

RS232 Ground-Loop Isolation: “creative” solution?

I have a RS232 connection that seem to suffer from different ground potentials at the two ends of the connection: The receiver signals a "break condition" in Realterm. As I understand it this means ...
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1answer
601 views

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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2answers
647 views

Optocoupler | Why a resistor is required in the collector?

In this circuit, if the resistor in the collector R1 is 0 Ohms, the circuit doesn't work. That is, the output will be 12V DC signal as it is from the battery. And if R1 is non-zero, then the circuit ...
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1answer
319 views

Opto-isolator to directly drive load

I need to control 8 12V automotive relays with an arduino. I have two PS2502-4 optoisolators. The relays are 12V with a coil current of 75mA. The transistor side of the optoisolator can handle ...
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173 views

Sensing 12v inputs in 3.3v system

Sorry if this has been asked before, but I searched for a while and didn't find anything that exactly answered my question. I would like to sense the "dummy lights"(oil, neutral, etc.) in my ...
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2answers
499 views

Low power method to turn Raspberry Pi on or off using an Arduino

I want to use an Arduino to control power to a Raspberry Pi. The power supply to this system is a solar panel with rechargeable cells, and the Arduino will turn the Pi off to preserve power in ...
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1answer
125 views

How do I pick the right resistor for an optoisolator given a desired current?

This is a follow up to this question, but isn't specific to the other one. This is both an ohm's law question and a 'how does one interpret data sheets' question. I want to minimize the current I ...
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4answers
634 views

Using an Opto-Isolator to detect 120VAC on a Microcontroller

I am designing a system where I need to know whether or not 120VAC is present on a specific wire. The system is in line with a fuel pump system, and I need to check to see whether or not the pump is ...
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1answer
360 views

Controlling multiple triacs with microcontroller for light dimming: where to use optoisolators

I want to control (dim) multiple mains lights using triacs and a microcontroller. (One triac per light). I want to keep both the costs and component count as low as possible. Is it necessary to have ...
2
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1answer
205 views

Isolated vs non-isolated triacs

Bt136-600 is an example of a non-isolated triac, while BTA08 is an example of an insulated triac. What is the difference between an isolated and non-isolated triac? They seem to have the same symbol ...
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288 views

Ask a way to pass high frequency PWM trough PC817(PC847)?How to realise this goal trough push-pull?

I am using PC847(datasheet )to isolate a PWM control signal from CPLD. I will describe my design .When duty cycle changes from low to high, the forward current changes from low to high, so I have to ...
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1answer
516 views

Optocoupler with 220V DC

i need help from you. I want to use 220V DC input to microcontroller. For this purpose i have to use optocoupler, so how can i choose optocoupler with input for 220V DC? Thanks!
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67 views

Using TLP280-4 with STM32F1xx MCU

This is a continuation of my previous question. Olin Lathrop explicitly explained me the previous question, but also set thinking on the exact way of connection the optocoupler to a MCU input. I ...
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2answers
252 views

How to use electrically isolated weak signal for Arduino interrupt?

I'm trying to use the signal generator from a DSO Nano v2 to drive an Arduino interrupt for testing purposes. I have measured the output of the signal generator at approximately 13mA @ 2V DC. I have ...
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1answer
735 views

TLP280-4 Optocoupler on 12/24V inputs

There is a STM32 device which has to detect several signals from other devices. The voltage of these signals can be 12V or 24V. Also these signals can be positive (i.e. 12/24V) or negative (connected ...
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1answer
353 views

connection from an comparator to an optocoupler

I have the circuit below to decode a signal that is defined as Logic high >9.5 V and Logic low <6 V To determine the ...
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2answers
128 views

how many resistance do i need to safe the LED of PC814?

if i have a input of 5v (arduino HIGH) on the LED of a PC814, how is the value of the resistance that i must use before that, so i don't burn the led? ...
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1answer
4k views

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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2answers
527 views

How to switch between a solar panel and battery?

A 12v battery is being charged from a solar panel. When battery is 12v solar panel is disconnected from battery and connect the load with battery. And again solar panel is connected with battery when ...
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1answer
159 views

Why is there a minimum Ic for a optocoupler?

I got confused when I saw this on a HCPL-181 optocoupler datasheet. You can get the datasheet here: HCPL-181 datasheet. So what would happen if the collector current goes below 2.5mA? (In fact I ...
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2answers
911 views

How to de-couple DMX512 with opto-isolators?

I'd like to build a DMX512 device. The problem I have is how to decouple the device from the bus. I decided to use opto-isolators, but how should I wire the diode part of the isolator? Since I need ...
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1answer
282 views

Optoisolator always on on the high-voltage side

I am building a simplified version of this circuit: As far as I can tell, it is a pretty standard design. The load will be a dumb resistive heater (this is a sous vide project). For now, the ...
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441 views

How to connect RS232 (“Opto-RS232”)

--Background-- I'm setting up a pretty standard RS232 interface from a digital caliper to a microcontroller, via a MAX232 chip (or in my case, MAX3222, which is the 3.3V-supply variant with 2 ...
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381 views

How to implement a delay OPTOcoupler input there by the circuit remain on for the next 1 second

I have another new project , the project is simple one when a call lands to the mobile an ac machine is triggered and it turns off when the mobile ring stop , for that i have used this circuit The ...
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1answer
1k views

how to put led to indicate the signal is functioning

I want to connect an input signal to pc817 and the output to a microcontroller. I don't know how to put the LED at the input to indicate that the input signal is working. For example my input is ...
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267 views

What is “Saturated CTR” of an optocoupler?

For example, in the datasheet of 4n27: . So what is saturated and what is non-saturated CTR?
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3answers
556 views

An opto-coupler/triac oddity — is it a problem, and is there a solution?

I'm using VO2223A opto-coupler/phototriacs to drive some low-current mains lighting with a PIC controller. All are working fine, but when the (DPST) mains switch is first turned on during system ...
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2answers
2k views

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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4answers
1k 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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617 views

How do I select an optoisolator to both provide zero crossing to a uC and controll a triac?

This application note states that zero crossing detection can be achieved in an AVR with just a couple of resistors. However, it forgoes galvanic isolation and this is not acceptable for me. I would ...
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3answers
281 views

Efficiently driving 8 low-current Optocouplers

I'm looking to drive a bank of eight FOD4216 random phase triac drivers. I'm looking specifically at the (insanely expensive, $3!) Fairchild FOD4218, which needs 1.3mA to switch. 8 * 1.3 = 10.4 mA ...
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1answer
274 views

how to design a switch which works when an input of 0.10 is applied

i have an alarm clock , it's output voltage to the alarm buzzer is around 0.15 volt , i need to attach an electrical appliance to make it operate on scheduled time , for that i had used this circuit ...
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1answer
1k views

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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4answers
867 views

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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1answer
137 views

VO2223A datasheet query — pin 5

This is a follow-up to a previous question, regarding the VO2223A opto-coupler/Phototriac. My understanding of the chip is that the IR LED triggers a phototriac, which in turn drives the gate of a ...
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412 views

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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282 views

Ring detector circuit, transistors not fully activating

I am attempting to build a ringer interface circuit, and I’m running into problems that are over my head. The purpose of the circuit is to buffer the output of a central telephone system that goes to ...
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1answer
2k 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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1answer
194 views

Multiples voltage on a optoisolated MCU input problem

The problem Handle digital inputs on a MCU, the input could be 5V, 12V, 24V or an open collector. My solution My approach is based on jumpers, given the fact that the inputs dont change behavior in ...
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3answers
783 views

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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1answer
319 views

Why do they add a TRIAC after an MCP3020 optocoupler?

I have a relay circuit (I use it instead of a relay) that uses a MCP3020, which I think does the physical separation of the two circuits (it's a LED and a photo cell inside a chip) and a BTA08 TRIAC. ...
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1answer
1k views

AC detection for microcontroller

I need to monitor the state of multiple relays carrying 110VAC and 60VAC using a microcontroller (I will probably use an Arduino) to ensure the relays are working properly. To do this I have figured ...
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3answers
435 views

Fast opto-isolation with open collector output without VCC

I have a two wire communication channel, with a data line and a ground line, with the data line being pulled high via a resistor on the receiving end. I am supposed to send information on this line by ...
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4answers
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Did I use this optocoupler correctly?

I'm planning on using this optocoupler in a PCB I'm making. I've never used one before so I want to make sure I'm doing this correctly and got the right numbers off the data sheet. The image below ...
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184 views

Triac datasheet values

I have a Triac that I want to use to control low voltage (~16 V) AC. The data sheet is found here. It specifies that the peak gate voltage is 5 V with a peak current rating of 2 A (which seems quite ...
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1answer
237 views

Calculating max wattage load for opto-triac

Are there any guidelines? Do the guidelines differ depending on resistive/inductive/reactive loads? For example, the Vishay VO2223A is rated up to 1A. At 110V it seems it can switch up to a 1 A x ...
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2answers
1k views

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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2answers
2k views

How could I create two separate ground areas with Proteus?

I need to design a PCB layout to a system using an isolated communication with optocouplers, what means that I need separated ground areas, each one on one side of the communication that I want to ...
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3answers
3k 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 ...