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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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31
votes
3answers
14k views

How can I detect a power outage with a microcontroller?

I have the following power supply configuration: AC MAINS -> UPS -> 24V POWER SUPPLY -> 5V VOLTAGE REGULATOR -> PCB (microcontroller). What's the best solution to detect the power outage on the mains ...
2
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6answers
8k views

Confusion with TRIAC firing and zero crossing point

The reason for firing a TRIAC very close to the zero crossing point is explained as to avoid RF or EMI interference. Below is an excerpt from a book: What I'm having trouble to understand is that, if ...
2
votes
2answers
6k views

How to sense the zero crossing of current?

I am trying to sense the power factor angle using microcontroller. Now the mechanism that I have thought it that Measure the zero crossing of voltage When the voltage zero is sensed, start the ...
14
votes
5answers
5k views

detecting zero cross in ac?

I need to detect zero crossing for a soft starter. A long while ago, I have done it using a 1 Mega ohm resistor directly connected to micro controller at one side and live power at another side. I was ...
4
votes
3answers
11k views

A question on zero crossing versus random-fire SSRs

Figure 1. I have the above mechanism, where I control a single-phase fan motor's switch. I mean instead of a mechanical switch, an AC/DC SSR is switching ON or OFF from a remote place by a constant ...
5
votes
4answers
11k 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 ...
12
votes
2answers
4k views

How do I read a datasheet for a solid state relay?

I'm looking to use several (12-18) solid state relays to control a set of water valves (24V AC solenoids, 20ma holding current, 40ma inrush current), and I'm having trouble finding suitable parts, ...
2
votes
4answers
595 views

Would this lazy zero cross detector work?

Task: Design a ZCD for 230VAC to be interfaced to an atmega168, 5VDC. The pictured optocoupler is SFH620A-3. I have on hand 1/4W E24 resistors. I am extremely lazy and want to go away with as little ...
4
votes
2answers
3k views

What does 'random phase' means in a triac driver?

I'm using this triac driver to control a triac. In its datasheet it says 'provide random phase control of high current triacs [...]'. What does that mean? It doesn't have zero-crossing detection?
1
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2answers
6k views

Do I need zero-crossing detection for controlling a heater?

I need to control a heater element (about 500W) using arduino. For switching part I would go with zero-crossing SSR or zero-crossing optoisolator and triac (the second seems to be cheaper). The ...
11
votes
3answers
15k 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 ...
11
votes
4answers
36k 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
4answers
20k views

Arduino 230v Light bulb dimming

Hey guys i have done a lot of research and testing on different circuits for 230v(50hz) or 220v light dimming, but i cant get my arduino to dim my light. This is the last thing i tried. made this ...
3
votes
1answer
11k views

Why do we prefer zero-crossing optotriacs for driving triacs?

I usually see a special type of optotriac which has internal zero-crossing detection circuit in it. This type of optotriac is generally used for driving triacs. But, I don't understand its necessity. ...
2
votes
1answer
10k 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
3answers
1k views

How to create a zero crossing detector using a full bridge wave rectified circuit

Currently 1) I have a full bridge wave rectified ac waveform of 10Vmax. 2) I also have a potentiometer adjustable DC waveform. 3) My rail voltages are +12V and -12V. 4) I currently supply my full ...
1
vote
1answer
88 views

A problem regarding connecting the grounds within two seperate circuits

Figure 1 I am trying to design the above circuit for my project to create zero crossing detector as shown in the above figure. This configuration was proposed originally by the member named "...
0
votes
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 ...
0
votes
3answers
5k views

Zero crossing detection and Light dimmer

I am confused by zero crossing detection of opto-triac. I know what is the zero crossing detection or switch. (ZCS) Zero crossing detects what is the point that wave is going to positive to negative ...
0
votes
4answers
670 views

Linear power supply + zero-crossing detection on transformer secondary

Having read this comment, I'm a bit concerned about whether one of my projects is going to work: simulate this circuit – Schematic created using CircuitLab The comparator is also inside the uC,...