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Questions tagged [opto-isolator]

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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1answer
59 views

Is this optocoupler driving relay circuit reliable and works great?

This is the circuit that I have, the optocoupler is an EL817 and the transistor is a BC817, the 24V relay is an Omron g2r_1_e, a 24V coil relay. But when the optocoupler input is floating (not ...
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0answers
34 views

BT137 triac turns-on uncommanded?

I am working with the following circuit, which is from the MOC3043M datasheet with a BT137 at the location of the unnamed triac: This circuit work fine for me if I leave the snubber out. However, ...
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0answers
54 views

Is it necessary to opto-isolate a darlington array output?

I've got the following circuit going: A Vishay opto-isolator (CNY74-4) that takes input from buttons that work on 24V, and outputs to microcontroller pins (an Olimex ESP32-PoE-ISO in my case). A ...
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0answers
24 views

Using Single isolated DC-DC converter for multiple opto-couplers in same circuit

I need to drive 4 MOSFETs with PWM of certain set frequency, whose outputs are connected to batteries. These 4 batteries are in series. I need to isolate input and output. Can I use a single Isolated ...
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1answer
37 views

Is 1.4mm Pad Distance at Optocoupler Pins for 230V/50Hz Mains Detector Enough?

For a project, I use an optocoupler to detect 230V/50Hz AC on a line - if a light switch connected to mains is pressed. For my calculation, I use 240V as a maximum AC voltage. It will limit the ...
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1answer
405 views

Creepage Distance in Altium Designer

I have a design with a high voltage and a low voltage part. Between the two I need to have a creepage distance of 8mm. Some optoisolators I use in my design are not wide enough on the PCB footprint, ...
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1answer
222 views

Overvoltage protection for AC relay dilemma

I am currently designing a safety-related device that has to open a relay when a certain event occurs. During most of its life, this relay will be closed, and only open if the safety event occurs, ...
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2answers
82 views

Are mechanical relay signal pins isolated from the output?

I am going to use a magnetic mechanical relay to switch 240v AC. I am using MPC250D6Z05APT, in its specification it did not say that the 5V signal is isolated from its output upon failure of the ...
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4answers
4k 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
221 views

Induced power supply noise on switch contact

I have a circuit that has a 24V section and a 5V section, separated by opto-isolators and an isolated DCDC converter. Both sides of the DC-DC have decoupling caps, and the MCU has one per Vcc pin. ...
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1answer
4k 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 ...
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3answers
86 views

Driving relay directly from optocoupler, what is best?

I'm designing a smart socket using an ESP-32 and a mechanical relay that can drive 5A at 240VAC. Following typical relay driving circuits, I would like to use an optocoupler between the MCU and relay. ...
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1answer
30 views

Optocoupler output current selection

There is a solid state relay (AQH1213) that switches the load to 220 V using 5 V (Arduino). The insulation voltage between the low and high voltage circuits in this relay is 5 kV. The challenge is ...
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1answer
45 views

Precision opto-isolator voltmeter circuit

I'm trying to use a LOC110P to make an isolated voltmeter. Here's the schematic of the important bits: The left-hand side of the circuit is actually AC powered and the intent of the circuit ...
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1answer
34 views

TLP281-4 optoisolator circuit question

I am working with TLP281-4 optoisolator, there is a board which used this IC in it. It connected like this: Why can't I connect 5V to the collector and take the output directly from between emitter ...
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0answers
18 views

Triac gate and T1 short circuit forever with inductive load

I am using MOC3042 with BT139 and snubber 390ohm/2W and 10nF/400V to on/off motor from microcontroller, I can't find data about the motor as it's an old one but it drives quite large shutter
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2answers
122 views

2EDN mosfet driver burns out when connected to PWM signal

Good day everyone, I am building a motor controller for a 250W DC motor. Today I was testing a part of my design, but somehow the MOSFET driver did not work. The Arduino send a 50% square wave (4kHz) ...
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2answers
73 views

Flipping Output Logic

I have the following circuit: (source: siteonlinetest.com) The diagram above has a pot between VCC, LM393 and Ground, on my board pictured below this is replaced by a voltage divider with two 10k ...
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1answer
159 views

MeanWell 3-in-1 dimming

I've got a constant current MeanWell LED driver that has 3-in-1 dimming (100k potentiometer, 0-10V signal or 10V PWM), and would like to control the dimming with a microcontroller. I found a few ...
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3answers
101 views

Can you and/or why should you not replace optocouplers with transistors when dealing with slightly different voltage

I stumbled upon this: https://gyazo.com/9f495ed8e9005ab440db8061839f412a so the mdb bus is communicating at a 34v level and the other side is at 5 or 3.3v why are they coupled with a optocouplers ...
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2answers
121 views

Voltage sampling from 220vac to 5vdc

I made a 1 phase to 3 phase inverter using arduino and IR2104 to control the speed of an induction motor and it is working perfectly. To complete the protection scheme, I need to monitor voltage of ...
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4answers
3k views

Interfacing a button to a microcontroller (and PC) with a 50 m long cable

I am designing a board that will be plugged into a computer and will read the status of a button ~50 m away in an office environment (it's actually a lot closer, but the cable is long). I think ...
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2answers
47 views

Using a Optocoupler - Determining Parameters

I'm looking at possibly using an optocoupler to drive a higher powered circuit from a lower powered one. This is the device I am looking at: http://www.vishay.com/docs/83641/il755.pdf The circuit I ...
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2answers
58 views

How can I improve this digital-output / digital input (automotive)

I'm creating some circuits required in a student-built electric-vehicle application. There are no heavy loads on the low-voltage +12V system. What I have below is a circuit that does some threshold ...
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1answer
35 views

Resistor power dissipation when driving optocoupler from ac mains

I followed this: https://learn.edwinrobotics.com/230v110v-ac-mains-detection-using-arduino-raspberry-pi-and-esp8266-thing/#Step2 With the exception that I used an LTV-814 that doesn't require a ...
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1answer
44 views

Raspberry Pi input protection with optocoupler?

I need to isolate a noisy input to a Raspberry Pi 4. Would this be the most correct way to implement it? I feel like the protection on the input side of the Pi is overkill. Note: Schematic uses a ...
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2answers
55 views

24V signal to drive led

I have a PLC which gives 24V DC output. I would like to drive an external LED using 24V. Is this the correct way to drive an led? Which is the right method let me know any changes needed. simulate ...
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2answers
59 views

Tri State/Floating Signal Detection

I'm working on a project for automotive environment in which I need to read signals from the power mirrors switch in a microcontroller. The power mirrors switch controls the mirror's moving directions ...
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1answer
194 views

Automotive Arduino

I was designing a circuit to manipulate in's and out's in a car. I use a step down converter to power up the Arduino. The inputs, in the left of the Arduino are: GIN : General grounded Input. ...
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2answers
2k 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 ...
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1answer
463 views

Is the ground necessary with an opto-isolated RS422 signal

I have 8 opto-isolated RS422 ports to install. All of them are coming from a single PC card. It provides the opto-isolation for every RS422 port. Every signal is opto-isolated from the PC ground and ...
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5answers
605 views

Diminished data rate with logic output optoisolator

I am using a logic output type optoisolator (H11L1S) that has a nominal data rate of 1 MHz, yet in practice I can't even achieve 100 kHz. Where am I going wrong? Is this maximum data rate ...
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0answers
31 views

Triac design for switching load to resistive heater

I'm designing a triac-based relay circuit to switch ac mains on-off to a resistive heater. The app note (AN-3004) for the opto isolator I am using, the MOC3061, suggests using a gate resistor value ...
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1answer
935 views

optocoupler H22A2 driving a plc input

https://www.vishay.com/docs/83741/83741.pdf example 2 I have existing H22A2 optocouplers that I am trying to run 12vdc through to get a plc input to turn on and off. I am using a 1k resistor on the ...
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1answer
30 views

Driving a TC4428 using PC817

I want to drive a mosfet using a mosfet-driver (TC4428). The frequency of turning on-off of mosfet is 5-10 Hz (yes Hz) and duty cycle is 10-20%. I use PC817 as ...
2
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1answer
57 views

230VAC line voltage sensing using MCU pin

I Am designing a circuit to detect the presence of AC line voltage.It is basically to detect the switch On/OFF for a load. Here is the circuit. Here Input resistor ladder to step down the voltage. ...
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2answers
67 views

Replace optoisolator with a resistor

I found this circuit that I wanted to quickly implement. He is using an optoisolator and feeding back the output using it. I understand that the optoisolator is isolating the sensitive circuit from ...
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2answers
65 views

Reverse Polarity Optoisolator

I am looking to detect, if battery is connected to board or not, by adding optoisolator to a battery and connect it to micro controller, before reverse polarity protection circuit. (Which is MOSFET ...
0
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1answer
594 views

Latching/Non-Latching Relay Driver Circuit with darlington optocoupler

I'm designing a circuit where an ESP8266 controls two types of relays, a single coil latching relay and a normal non-latching relay. The relays are power relays use to control low power electrical ...
2
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1answer
664 views

High side RC ESC switch

I've been designing a test bench for RC propulsion systems and for that I thought it would be nice to be able to switch the power to the ESC on/off. For this I designed a simple circuit which I ...
2
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3answers
105 views

Why optocouplers for MIDI Out/Thru?

I found this article: midi-in-through-out Credits by Zynthian I like that it has notification LEDS for MIDI in/out/thru. However, I also notice there are optocouplers for MIDI Out and Thru, while ...
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0answers
106 views

Optocoupler Failures

I am designing a small PCB that has several digital and relay outputs. The signals to and from the board will be 24VDC, while the logic on the board will be 3.3VDC. There will also be 12VDC for the ...
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2answers
60 views

Voltage drop after optocoupler

I don't know what's wrong... I have an ATTiny13 which gives a dummy impulse turning a fan on and off every 2 seconds; so the plan. I attach two power sources (for dummy purpose) before and after the ...
2
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1answer
673 views

How safety capacitor replaces optocoupler

I see some phone chargers using safety capacitor (after some research I found its safety capacitor)But not optocoupler to isolate in and out . How safety capacitors replace the optocoupler
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1answer
58 views

Modification to Arduino 12V Detection Circuit

I'm upgrading the interior lights on an older model vehicle. The plan is to tap into the very simple lighting circuit (always hot with a switch for on-off-door) to detect each scenario. Light switch ...
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5answers
5k views

Can an opto-isolated input be analog?

Title says it all: can an opto-isolated input be analog or are they intrinsically digital? Why: I am looking to purchase a relay control board and am deciding between a few options. Here is my ...
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1answer
51 views

What is the expression for collector current (Ic) in function of CTR for optocoupler?

I'm just asking about expression for collector current (Ic) of optocoupler in function of CTR because my simulation results doesn't fit with the CTR=Ic/If equation. Simulating the part CNY17-3 with ...
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2answers
85 views

Zero Crossing Signal Timing

I have a zero crossing circuit for dimming lamps exactly like the below According to my calculations: \$ I_{R7} = \frac {V}{R} = \frac {3.3}{10k} = 0.33~mA\$. Considering TCMT1109 transfer ratio ...
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2answers
2k views

Isolating PWM From H-Bridge

I have a H-bridge based on FAN7392 drivers. This bridge works at 350VDC to output a approximately 240V 50Hz waveform. This circuit is isolated from rest of the board and I would like to maintain the ...
1
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1answer
78 views

Optocoupler - Make active low output at active high

I'm currently working on a project and it consists of amplifying a 5V signal from an Arduino to 24V. I made my circuit and hooked it up to a oscilloscope and it shows that the output of the ...