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.
1,290 questions
2 votes
1 answer
198 views
PNP and NPN BJT circuit function
In a schematic for a flyback converter using TL494CN, I have come across this circuit in the feedback loop: Source GW Instek SPD-3606 from here For completeness here is the other part of the U210 ...
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4 votes
2 answers
215 views
Is optocoupler bias resistor and shunt regulator reference resistor value sufficient?
I am building one power supply and this is the circuit diagram of the isolation part. my question is : Is the value of the resistor that connected to the anode to the optocoupler(R18) and bias ...
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1 vote
0 answers
51 views
Do you have any ideas for components I could use to replace these ideal switches in LTspice?
I’m currently designing an electrical circuit to measure the voltage level of a PWM signal as part of my studies. I’m in my third year of a Bachelor’s degree in France, in a program called Electrical ...
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4 votes
5 answers
201 views
What board does an optocoupler go on
I have a requirement to provide an optocoupler for the purpose of enabling power on another board. I am wondering where physically the optocoupler should go on. Should it go on the driver board or ...
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2 votes
6 answers
329 views
Why there's no limiting resistor at the base of the TIP122 in this device?
I have this circuit of a solenoid controller I have, and I'm trying to understand a few things about it. I simulated it in FALSTAD. I used a relay in place of the solenoid in Falstad. Also two NPN ...
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0 votes
3 answers
92 views
how to short two pins in solid state manner of a to turn on a device
I have an inverter, which I want to turn on/off remotely and designing a circuit using ESP8266. As usual the inverter's control board has two special pins and if i short them using a metal wire or ...
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2 votes
3 answers
216 views
How to properly handle floating input on an optocoupler LED with long wires in automotive environment?
I am working on a circuit that uses a PC817 (or LTV-847 for multiple channels) as an input stage for my microcontroller (via MCP23017). The installation is in an automobile, and the input comes from a ...
2 votes
3 answers
268 views
How does zero crossing opto-TRIAC not cause self-triggering of main TRIAC?
I want to turn on/off LED bulbs and AC fan from a microcontroller. No chopping control is required. I only needed isolation and low noise soft switch that's why I've chosen a zero-crossing opto-TRIAC ...
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1 vote
2 answers
147 views
How can I get this optocoupler to work with both the Power Supply and 9V battery?
I'm currently working on a project where I have a circuit that needs to be updated since it needs to have some sort of isolation added to the terminal block inputs to prevent the user from damaging ...
- 559
-1 votes
1 answer
89 views
Optocoupler saturation
IC MPN- FODM2701R2 I am giving If=5 mA current through diode. CTR is 300%. Ic current through transistor will be 15 mA. R1=0 Ω. R3=1500 Ω. Therefore I am limiting the max Ic current to 3.33 mA. ...
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0 votes
2 answers
133 views
100nF capacitor at Digital Input
What is your opinion on using a 100nF capacitor in the digital input circuit with the PC817C optocoupler? I am using this capacitor to eliminate false triggering from the pushbutton. When the ...
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1 vote
1 answer
112 views
How to connect the ACOUT pin of the BM1Z102FJ to a STM32G070RB MCU?
So, when i was checking the BM1Z102Fj datasheet it mentioned its ACOUT Pin voltage range from 0-0.3V to +29. Now I am using a STM32G070RB which has highest +5V tolerant pin only not more than that. ...
0 votes
0 answers
70 views
Triac circuit always on
I have a circuit that's supposed to be used for switching a lamp. Unfortunately, regardless of whether there is a signal on the optotriac or not, there is always voltage on terminal L2 and the lamp ...
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1 vote
0 answers
40 views
How to drive a controller input from driver output
I am trying to connect an alarm circuit from a motor driver to the controller board. The driver has an alarm pin that goes to ground during alarm. Is is called a "passive" pin, so I think I'...
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3 votes
2 answers
538 views
PC817 optocoupler is not working as expected
I am facing with a problem on PC817. As per circuit examples on data sheet I build an test circuit. Accoring to the data sheet IR led activates as soon as power supplied on 1 and 2 and permit to pass ...
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