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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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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4 votes
1 answer
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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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2 answers
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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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1 vote
1 answer
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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 ...
3 votes
0 answers
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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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1 answer
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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 ...
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4 answers
219 views

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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2 answers
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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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4 votes
2 answers
174 views

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 ...
0 votes
3 answers
171 views

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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2 votes
1 answer
363 views

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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1 answer
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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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1 answer
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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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1 answer
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Zero current switching SMPS with common emitter or source

Is there any? Is it even possible that such arrangement could exist? Im interested in SMPS where both, turn ON and turn OFF processes of all switching elements happen at zero current through that ...
2 votes
4 answers
1k views

Finding zero cross of AC signal digitally

I'm measuring 50/60 Hz with STM32 microcontroller. The signal comes from current transformer. I'm adding a DC shift to the signal equal to 1.65V. As the signal is riding in 1.65V, this will be my zero ...
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1 answer
111 views

Generating a cross zero pulse wave

For a project I need a zero crossing wave like this Its generated by an inductive coil of a distributor of a car engine where that signal triggers a CDI (capacity discharge ignition) when it falls ...
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1 answer
143 views

Switching Relay at Zero_Cross Point

I'm controlling 4 Relays(10A) with a controller. While randomly switching it without zero-cross my controller gets restart. To avoid this I'm switching relays at the zero-cross point, But my question ...
2 votes
3 answers
589 views

Zero Crossing Detector Circuit

I am working on a zero crossing detector circuit. Can anyone please explain the function of highlighted circuit?
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Zero cross control for inductive loads

Is zero cross control acceptable for small motors? I know it is bad to have voltage and current out of phase for inductive loads but wanted to know if it would not be harmful to small motors (< 500 ...
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Doubt about zero-cross circuit

I have simulated the following circuit on MultiSim, and it seems to work well doing its job. The first element is a full wave bridge rectifier. At its output is connected the input of the zero-cross ...
2 votes
2 answers
453 views

Using a behavioral voltage source as a zero crossing detector for inductance current in LTSpice

I'm trying to simulate a buck converter IC in LTSpice (MP4569) based on the functional block diagram from the datasheet using behavioral voltage sources to represent the logic from the block diagram. ...
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2 answers
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Zero crossing circuit

I have made a simlpe zero crossing circuit to control the speef of a single phase AC fan through conduction angle control with a Triac. The circuit looks like this with the use of 4n25, an optocoupler:...
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3 votes
4 answers
1k views

Tachometer IC that does not require zero-crossings?

I recently built the basic tachometer circuit in this LM2917/LM2907 Datasheet shown below using the 8-Pin version of the device. I realize this circuit requires a VR pickup sensor, and so the LM2907/...
1 vote
1 answer
148 views

Zero Crossing Detector using comparator

I followed SNOA999 for a zero crossing detector using TLV7011 as a comparator. I am not sure about short-circuiting grounds between AC and DC power sources. My concern is creating negative currents on ...
0 votes
3 answers
287 views

Zero cross detector output

I have realized what I thought was a classic zero cross detector circuit using an H11AA1 chip: https://www.digikey.com/product-detail/en/on-semiconductor/H11AA1SR2M/H11AA1SR2MCT-ND/2094174 My circuit ...
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0 answers
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Need help in zero cross circuit by using op-amp

I worked on zero crossing circuit by using opto-coupler.Circuit is It is working okay.Zero_crossing signal is There is a 2-3 ms of signal loss is happening with 50Hz of AC signal.I don't want more ...
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Undesired noise on isolated zero-cross

I have a prototype board which I'm currently testing the signals of its zero-cross circuit. This is the schematic of the PSU, the power supplies of the low voltage part of my circuit (12V, 5V, 3V3) ...
1 vote
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LM741 Cross-Over distortion

Could anyone explain why I may see cross-over distortion in my output signal of this op-amp circuit? The input is a 1Vpp sine wave at a frequency of 10kHz, with no DC offset. I am definitely seeing ...
0 votes
1 answer
148 views

Momentary overloading of a mains transformer at low duty cycle operation - what could go wrong?

I'm planning on using a 120 VA Hammond 1182P12 toroidal transformer to deliver 24 VAC to a 2.5 Ω resistive load (a JBC C245 soldering iron cartridge), implying 9.6 A RMS, 230 W if continously applied. ...
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Need help to design efficient zero crossing CURRENT detector : clamp diode solution

I try to design a replacement potter's wheel motor controller for an old potter wheel. I have solve my zero crossing voltage detector and TRIAC command. Now I begin to understand the importance of the ...
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11 votes
3 answers
2k views

Very high precision zero crossing detection

I have a setup that is equivalent to a guitar string with pickup, with signals of similar frequency range. I have a simple zero crossing detector with a comparator and then just count the interval ...
1 vote
3 answers
622 views

Audiable pops when switching DC biased audio signal

In my previous question, I have asked how to DC bias audio signal for a crosspoint audio switching matrix (Switch array (crosspoint) and DC biasing of audio signal). I am using the following circuit ...
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2 answers
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Core-less transformer for Zero-crossing detection

If possible, what are calculations and precautions involved in making a simple transformer without core? The only purpose of this transformer is to trigger an opto-coupler for zero-crossing detection ...
2 votes
2 answers
1k views

HCPL3700 - 220V sensing circuit

I want to use HCPL3700 optocoupler for sensing 220V (line). I design a circuit but I want to ask some questions. HCPL3700 is an open-collector output so I pull-up Vout. In AC voltage sensing some ...
1 vote
0 answers
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Controling a Washing Machine AC Motor Using a Relay

I would like to control the motor of my washing machine using an Arduino. It's an old washing machine with a mechanical controller and an AC motor connected to a 12.5 uF run/start capacitor. According ...
2 votes
2 answers
459 views

Zero crossing detector inconsistency

I designed the following zero crossing detector using an FOD819S optocoupler (U5): The source of the optocoupler is connected to a MB6F full-bridge rectifier (D2) which is supplied by a 9V ...
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ZCD with PIC 18LF45K40

I want to implement phase angle control for a single phase ac fan. To achieve that we need a ZCD circuit interfaced with a microcontroller to get a pulse at zero crossing. As our circuit has some ...
0 votes
2 answers
164 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 ...
2 votes
1 answer
266 views

zero-crossing detection: to optocouple or not to optocouple?

That is the question. Most of the diagrams I have seen on the interwebs are of the opto-coupling school of thought: But the AVR182: Zero Cross Detector application note just throws in the resistors ...
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Tapping into a 5.1V transformer for a zero-crossing detection circuit

I want to make myself a reflow oven following more or less this guide: http://andybrown.me.uk/2015/07/12/awreflow2/ Here is the zero-crossing detection circuit diagram: Thing is I would like to cut ...
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