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.
14
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4answers
497 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, ...
9
votes
2answers
2k views
How do I select the accompanying components for an optocoupler?
I'm using an optocoupler (MOC3021) to sense the On/Off state of an electrial appliance using a microcontroller ATmega16L. How do i go about doing this? My mains supply specs are 230V, 50Hz. How do I ...
8
votes
3answers
10k views
How to drive a MOSFET with an optocoupler?
What's the proper schematic for driving this MOSFET from a microcontroller pin through this or this optocoupler?
The MOSFET will drive a motor @ 24V, 6A.
8
votes
2answers
959 views
Why Snub an Optoisolator?
I am using an optocoupler and a power triac to switch 120VAC supply to an ~108 watt fan. The datasheet for my optocoupler requires me to snub the optocoupler output when I'm switching an inductive ...
6
votes
4answers
512 views
Optoisolate 2MHz SPI communication
I need to isolate the SPI communication between two chips.
The bottleneck of the communication is on the slave, which apparently can handle up to 2MHz SPI clock ...
6
votes
2answers
418 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 ...
6
votes
4answers
364 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 ...
5
votes
6answers
407 views
Optoisolate two ICs sharing same power supply
I have two ICs. The former acts like an ADC, measuring the voltage in a power outlet and transmitting the result to the last. Both ICs requires 5 Volts to work.
I ...
5
votes
4answers
4k views
Digital Dimmer With Microcontroller
I want to build a digital dimmer for resistive Loads.
I have found this circuit for that:
The input voltage is 220VAC 50Hz.
The red box in the picture is for ...
5
votes
2answers
2k views
opto isolated arduino input
I want to protect a pin with an opto isolator to get an external signal from an electrical meter (35VDC max, 50mA max, 240ms pulse width). The purpose is to count the pulses.
Do you have some ...
5
votes
3answers
3k views
When should I fire the TRIAC's gate when controlling an inductive load (AC motor)?
I'm using a combination of opto-triac + TRIAC to control a 230V AC motor with a microcontroller. For detecting the zero-crossing of the voltage I'm using another optocoupler.
I know that the AC ...
5
votes
3answers
247 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 ...
5
votes
1answer
189 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 ...
5
votes
3answers
249 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, ...
5
votes
1answer
130 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 ...
4
votes
4answers
399 views
Why are optoisolators white?
I've noticed that most of the opto-isolators (optocouplers, opto-triacs) have a white package. Why is that?
4
votes
2answers
478 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?
4
votes
4answers
946 views
Sanity-check on snubber design
I keep frying resistors in the following optocoupler and triac snubber circuit, and I'm not sure whether to attribute this to bad design, or to faulty components.
There are no observable sparks at ...
4
votes
5answers
2k 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 ...
4
votes
1answer
172 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 ...
4
votes
1answer
358 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 ...
4
votes
1answer
366 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 ...
4
votes
1answer
122 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 ...
4
votes
3answers
1k 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 ...
4
votes
1answer
391 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 ...
3
votes
3answers
875 views
Shift Register output to Relays
sorry for the length.
This is a continuation of my recent question. I have an optocoupled 8-relay board that I’m trying to connect to my microcontroller. I have placed a 74HC595 shift register inline ...
3
votes
4answers
2k views
120VAC 60Hz Zero Cross Detector
I'm designing a digital phase-controlled light dimmer, and I need a zero-crossing detector circuit. From what I've read, it's a bad idea to wire the AC main directly to the microcontroller through a ...
3
votes
1answer
146 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 ...
3
votes
1answer
63 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 ...
3
votes
2answers
726 views
Is a protection diode needed on a TRIAC optocoupler and what for?
Please refer to page nine of the Sharp S108T01 / S108T02 datasheet:
Is this diode needed - why/why not?
How do I choose the correct diode, if yes?
UPDATE: Thank you all for your educational ...
3
votes
2answers
894 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 ...
3
votes
1answer
446 views
Zero Cross Detection Circuit for line voltage [duplicate]
Possible Duplicate:
How can I detect a power outage with a microcontroller?
I'm doing some research with the goal of eventually creating a light dimmer controllable from a micro controller. ...
2
votes
3answers
924 views
Measuring voltage/current digitally on two separate power supply rails
I'm designing a dual-rail DC power supply, with the two rails completely separate (except for sharing a dual-secondary transformer). The main design should work as-is, only by adding a fuse + mains ...
2
votes
2answers
110 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 ...
2
votes
1answer
625 views
How to properly Bias a Opto Coupler
I had some problems setting up a Opto Coupler today. The data sheet is here. I set it up putting a 470 ohm resistor to ground from the cathode (pin 2). I am understand the selection of this resistor ...
2
votes
1answer
690 views
Power MOSFETs and Gate drivers
I'm trying to finally apply what I learned at university in the course of power electronics.
However I find that both that course and most of the books / online references are lacking on some points.
...
2
votes
1answer
338 views
how to interface HCPL-3700 optocoupler to an input pin of ATmega16L
I want to detect logic of the mains supply (230VAC, 50Hz) and feed the output of HCPL-3700 into ATmega16L. I read through the datasheet but could not understand how to calculate the resistor values. ...
2
votes
1answer
170 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 ...
2
votes
1answer
100 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 ...
2
votes
2answers
303 views
Isolated MOSFET output stage calculations
I am a newcomer in this wonderful world of electronics trying to design my own PLC.
So far I have designed a single output stage that I think will work, but it would be great if i could have any of ...
1
vote
1answer
837 views
How do I choose my optocoupler?
I need to drive a solenoid with a MOSFET. And this command have to be isolated with an optocoupler but I don't know how to choose it. What characteristics do I need to watch in the datasheet? What is ...
1
vote
1answer
501 views
Is this galvanic isolation?
I'm doing a project which consists of 2 big parts: a control part (a microcontroller with I/O pins expanded, USART-to-USB, a RTC, an EEPROM, a LCD) working @ 5V and an actuators part (optocouplers for ...
1
vote
4answers
606 views
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 ...
1
vote
2answers
62 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?
...
1
vote
2answers
219 views
Connect a microcontroller to a gadget
Although I have average programming skills, I'm not far from being an noob concerning electronics!
I therefore want to kindly ask you to help me connect my (already programmed) Arduino Uno to the ...
1
vote
1answer
2k views
How to use a phototriac coupler to trigger the main triac?
I have in my box of parts a phototriac coupler, namely a Sharp PC3SD21NTZ (datasheet), which is a zero cross type. I don't know how to use it, but I've been meaning to learn for a while.
This part is ...
1
vote
2answers
507 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 ...
1
vote
1answer
222 views
Alternative to optocoupler? Other switching devices?
I have a part that classifies what kind of power I get on ethernet by presenting different loads. For example, the part needs to have a 100 Ohm resistor across two of its pins, and the part will ...
1
vote
3answers
540 views
I2C optocoupler separation - which IC?
I am designing a circuit which will have some external I2C sensors connected to it and thus I want to protect it from noise - via an optocoupler. I have to say that I am a complete novice to this all ...
1
vote
1answer
286 views
How to determine whether electrial appliance is On or Off using ADC or Optocoupler
I want to sense the On/Off state of an electrical appliance (e.g. light bulb 100W) using a microcontroller ATmega16L. How do i go about doing this? My mains supply specs are 230V, 50Hz
