# Questions tagged [zero-crossing]

Zero-crossing refers to detecting the point at which a sine wave reaches the zero point of magnitude. In AC circuits it corresponds to the point at which no voltage is present so switching at that point reduces interference.

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### Using a solid state relay, NC type to control an AC load

I need to control the shutdown of a load that operates with a voltage of 25V and a maximum RMS current of about 90 mA. This load is working almost always and rarely needs to be turned off. For which, ...
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### Zero crossing circuit with phase control

Beginner here. I am trying to make a "zero crossing" circuit with phase control. This is probably not the right name for the circuit. Basically, I have a sine wave (from the power outlet) at ...
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1 vote
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### Dimming light idea

I have this idea to dim a light. The problem is that my EBS simulation software won't allow me to see the actual result of the dimming. The only way to test it out is to physically construct the ...
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### BJT Zero-Crossing Detector for 40kHz Ultrasonic Signal - Distortion & Receiver Issues

General Information About the Project I am trying to design a zero-crossing detector circuit for convert the sinusoidal signal from an ultrasonic transducer to a square wave. Here is the image of ...
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### Schematic of a simple zero-crossing triac switch

I have a triac in a 60Hz 120V power line (as is often done for dimming) and want it to only switch on the power when the AC voltage is low (widely between -40V and +40V would even be fine). This is ...
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### Circuit that outputs signal A when AC sine is positive and signal B when AC sine is negative

I need help designing a circuit that outputs Signal A high when AC sine wave is positive and Signal B high when the sine wave is negative. It's part of a larger project that cycles power in a ...
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### TRIAC and zero cross detection

I am working on an IoT project to control the speed of my ceiling fan through my mobile. The problem is that the TRIAC and the fan speed circuit just won't work when it is on a PCB. I know it sounds ...
1 vote
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### How does this zero crossing detector circuit work? How can I modify it to work at lower supply voltage?

I've been working on a zero crossing detector circuit for audio modulating a flyback transformer. So far it's working great, but I have a few questions regarding the circuit and its operation. Image ...
177 views

### Low Voltage Zero-Cross Circuit

I'm trying to read the wind speed with my Raspberry Pi. I have an anemometer that produces between 80mV and 12V AC at 0 to 125Hz (it's basically a wind turbine). I have it hooked up to an Analog-to-...
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### Understanding violation of the common mode voltage range of the input in ZCD [closed]

Trying to reproduce an analog circuit using LM324 to have at output 100Hz squarewave 5% duty cycle from 230Vac mains frequency. The circuit has to be in sync with it. Picture and LTSpice simulation ...
1 vote
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### Right dimensioning of zero cross detection circuit

I need to detect the zero cross of AC main (220V - 50Hz) with an ESP32 to make a phase shift control of a resistive load. Searching the web I found this circuit but I have some doubts on how to ...
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### Triac Phase angle control Heating method

I purchased a soldering station (Product Link: Tenma 2064549. Just for give more idea. Not for taking about the product.) few years ago and replaced the heating element. After replacing heating ...
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### Will a zero-crossing SSR activate with shorted load contacts?

If I have a zero-crossing SSR switching 240VAC (e.g. this LS240D12), will the zero-crossing detection function if the load side is shorted? I know that zero-crossing SSR's can't be used with DC loads ...
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### Zero Crossing Detector

Thanks for your help in advance! I'm doing a zero cross detector for a microcontroller, PIC16F15223. I will be reading this as a digital input, and not as analog. The circuit is posted below. I know ...
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### Zero Crossing Detector for Microcontroller

Im trying to design a control circuit for charge a battery, for this i will be controlling the battery charge by a 40tps ( SCR ), phase control. So my little understanding for what i read is that i ...
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### Zero crossing detector - MCU interrupt is delayed

I'm trying to catch zero crossing (using below circuit) when it exactly happened. Rising and falling edge intervals are not equal and they need 0.3-0.7 ms to reach corresponding logic level. Let say ...
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### How to make 3-phase 230V AC zero crossing detection with Arduino UNO [closed]

I am working on making a 3-phase power control of a heating element using PWM control with an SSR. I have a problem making a zero crossing detection to control the duty cycle of the PWM to turn it on ...
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### When to use a non-zero crossing opto-TRIAC and when a zero-crossing opto-TRIAC?

I have two simple questions. From what I know, if we want to use an opto-TRIAC (with another TRIAC of course) to control an AC motor, if we want to use it as an ON/OFF switch, then I have to go for a &...
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### Zero crossing detection and full-wave rectifier for non-AC voltage

Our control signal that ranges from -5 to 5 V needs to be split up such that the magnitude and sign can be send through different wires. So, for example, a -3 V input sends a 3 V signal through one ...
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### Troubleshooting a ZCD TRIAC circuit

Can someone see what's wrong here? My 50 W LED light doesn't shine. Here is my code from the Arduino IDE: ...
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### LED-flash during powerup with my ZCD/Triac-circuit

Friends, I've made a ZDC-circut to dim my 230VAC LED-chip. It works fine except for a short, flashy, annoying blink when powered up!! It happens about 8/10 times when I switch the power on/off. Any1 ...
1k views

### BLDC back-EMF zero-crossing detection using comparators: resistor confusion

I am building a sensorless BLDC driver development board using an RP2040 chip and I plan on detecting the back-EMF using comparators. After reading quite a bit about the BLDC phases and methods to ...
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### Zero-Crossing Detector Circuit for a PWM-Generated Sine Wave

Given this PWM, How to detect a zero crossing without a dual-voltage supply? There is only VCC and GND. I've tried using a low-pass filter approach, but the PWM frequency is not guaranteed to be ...
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### Comparator output problem for zero cross detection

. Could anyone give me advice on this zero cross detection circuit I'm working on to allow for phase angle detection? Just to add I'm only a student so I'm very much still learning. My background is ...
1 vote
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### Choose appropriate opto-isolator for 230 Vac zero-cross detection circuit

I struggle to understand the datasheet for opto-isolators. I am making a 230 Vac circuit with a full-bridge rectifier. What should I look for when choosing an appropriate opto-isolator? I've been ...
194 views

### Low power isolated mains voltage zero crossing detection (without optocoupler)?

There are a lot of "classic" zero crossing detectors out there that drive an optocoupler more or less precisely around the mains voltage zero crossing. I am not so much interested in ...
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### Strange measurements on zero-cross detection circuit

I'm building a cross detection circuit op-amp. I did something like this, coming from https://www.circuits-diy.com/zero-crossing-detector-circuit/ : In my case, primary is 230V AC, secondary is ...
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### Zero-cross detection phase delay BLDC motor

Low-speed output: High-speed output: In the above circuit, output channel 1 (yellow) is a Hall signal and channel 2 (Green) is the ZCD output. There is a phase delay between channel 1 and channel 2 ...
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### Firing a triac with PWM

I want to use an ESP32 microcontroller to power a 3600 W load with a triac. Using phase control requires accurate timing and that is nearly impossible with a lot of code already running in the ESP32. ...
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### ROHM AC zero cross chip/circuit not working

I'm using the ROHM chip BM1Z003FJ to detect AC zero cross and send that pulse to the micro, the only problem is the ROHM chip never outputs a pulse. My circuit is shown below: The ACOUT pin should ...
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### Why my ACS712 current sensor accuracy so bad and scale non linear?

Below is my circuit diagram for ACS712 5A current sensor using peak detector circuit. Currently I facing 2 problems. i)zero cross dc voltage keep changing ii)The current scale is non linear and not ...
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### Why this ZCD not working?

I have a simple drawing of ZCD by using potential divider to stepdown the voltage feeding to the inverting and non-inverting input of LM358N. The simulation result as below In practical, I connect ...
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### PWM signal generator circuit does not work in real life

I designed the motor soft start circuit in the figure below. I ran the circuit in simulation programs, but when I tried it on a breadboard in real life, I could not get a PWM signal. When I examined ...
203 views

### Fixing overshoot in current regulation of AC electronic load

My AC electronic load (previous question here) shall have a constant-current mode. It is being simulated in LTspice. @devnull helped design the circuit for AC loads, but for simplicity's sake in the ...
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### How to guarantee clearance/creepage on mains side of an optocoupler used for 230VAC zero-crossing detection?

Update: Added a diode to protect optocoupler LED As stated in several safety standards (UL 60950 or UL 60750 for example,) we have to guarantee a minimum clearance/creepage between signals of opposite ...
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### Zero-cross detector does not detect all the zeroes

I'm trying to do a zero-crossing detector but it is only able to mark half the number of zero passings. It seems to work fine with input voltages of 10-20V, but when using a +120VRMS it checks only on ...
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### Suggestions to clarify comparator circuit

I'm confused with the next issue from school that I can't figure out and wasn't able to solve (this is homework already graded, but the teacher refused to explain me). I was asked to design and ...
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### What are the disadvantages of using NZC Optocoupler as switch

I've bought some MOC3023 to use with a triac for turning some home appliance on/off using an EPS8266. The thing is.. every place that I search says that for on/off the best is a zero crossing detector ...
1 vote
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### Unexpected Crossover Distortion

I created and built the following circuit: When the SWITCH is closed, the audio amplifier works as expected, with no noticeable crossover distortion. When the SWITCH is open, the amplifier still ...
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### Zero current detect circuit

I would like to make a primary side regulation (PSR) flyback converter, but I have one thing I do not understand. I read this document from ON Semi. If I want to do PSR, I need to detect the diode ...
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### Unexpected voltage shift in zero-crossing detector circuit

I have designed following circuit of a zero-crossing detector, which is supposed to amplify small sine wave signal and convert it to (digital) square wave. It uses one single supply op amp for ...
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### TRIAC phase angle control 120 VAC line ripple

I'm working on a phase angle controlled TRIAC dimming circuit (schematic attached below), and I'm seeing a lot of ripple/noise on the 120 VAC input as I near 50% power. I'm wondering what I can do in ...
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### Does a signal that doesn't change polarity charge a capacitor?

I'm wondering if a digital signal that does not change polarity charges a capacitor. If the signal has a frequency of 1 MHz, does that charge the capacitor faster? And if so, is it possible to ...
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### acs37800 zero-crossing signal timing problem

I'm working on a project that is using ACS37800 for measuring current and voltage and for detecting zero-crossing. However, there is some issues with the timing as the zero-crossing detection is off. ...
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### Optocoupler 4N25 cut and saturation for zero crossing detector circuit

This is my first time working with an optocoupler and I'm trying to find the right resistors for a zero crossing detector circuit that has a 4N25 optocoupler, but the values I've calculated are not ...
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### Resistors for zero crossing detector with optocoupler

I'm trying to understand how to calculate the right value for resistors R1 and R2 in this circuit using the 4N25 optocoupler, and with 12Vac. With 12Vac, Vp is 16.27v. In this case, the optocoupler ...
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### AC zero Crossing detection with transformer

I am working on a circuit that requires zero crossing detection. I detected the zero crossings of the 230 Volt AC sine with the help of a full bridge rectifier and a 4N25 optocoupler with a pull up ...
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### Detecting absence of current in transformer secondary

Beginner here. I'm trying to build a circuit which charges a capacitor to an arbitrary voltage in the shortest possible time. I want the high voltage part of the circuit to be galvanically isolated ...
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