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Results tagged with zero-crossing
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user 20218
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.
3
votes
Accepted
ZCD with LM358 not working
The LM358 is powered from 5 volts and you are forcing an input signal from the bridge that is rectifying a 12 V AC voltage. This usually means the LM358 will never work again.
The operational input r …
- 473k
8
votes
zero cross detector missing zero cross
The basic problem is that your AC source is not-isolated from ground. If it were then there would be no problem when you add the 10 kohm resistor that I recommended.
So, you have one incoming AC lin …
- 473k
2
votes
Accepted
Would this lazy zero cross detector work?
Make sure your resistors are rated for the voltage you are applying. Some resistors are only rated at 100V peak so watch this one.
With a total LED resistance of 125 kohm and the specified input capa …
- 473k
2
votes
Would I need a zero-crossing SSR for a reflow oven controller?
The design/guide is for using the oven AND a fan controlled from seperate zero-crossing SSRs. The oven is just a resistive heating element and could be controlled from a non-zero-crossing switch but i …
- 473k
3
votes
Will this zero-cross detection circuit work?
The rise/fall time of the opto is about 20 microseconds (1000 ohm load) and the time when the rectified voltage is close to zero is maybe 2 degrees of one cycle. At a 20ms period of AC, a couple of de …
- 473k
2
votes
Accepted
DIY zero-crossing circuit, how crucial are component values?
There's a basic problem with the circuit around the 2N3904 transistor and how it gets biased (more further down)...
For the resistors yes, and given the applied voltages, two in series will likely be …
- 473k
3
votes
Will a low-pass filter make zero-crossing detection less precise?
Will a low-pass filter make zero-crossing detection less precise?
I assume you are comparing one signal against another and that all signals are processed using the same hardware. In other words, …
- 473k
2
votes
Zero cross detector output
the timing characteristics are very far from the actual
zero-crossing
It looks pretty close to me - see the red lines I've added. In other words the middle of the peak of the yellow waveform …
- 473k
2
votes
Accepted
Circuit that outputs signal A when AC sine is positive and signal B when AC sine is negative
Op-amp precision rectifiers are the likely turn-to solution. Here's an example circuit: -
When the input is positive, the op-amp is prevented from creating an inverted (negative) output by D1 but, wh …
- 473k
1
vote
Accepted
Switching Relay at Zero_Cross Point
While randomly switching it without zero-cross my controller gets
restart
That's a susceptibility weakness of your controller.
To avoid this I'm switching relays at the zero-cross point
Sounds lik …
- 473k
0
votes
Zero current switching SMPS with common emitter or source
If you have an SMPS that stores energy in an inductor and then releases that energy (per cycle) to an output capacitor then you must "switch" when the inductor current is non-zero because if the curre …
- 473k
2
votes
Accepted
Zero Crossing Detection of ~ 400 kHz Signal with MCU
If you are dealing with an analogue signal and trying to convert it to a suitable square wave for frequency measuring you have to consider the effects of noise and implement some form of hysteresis so …
- 473k
3
votes
Accepted
Tachometer IC that does not require zero-crossings?
I realize this circuit requires a VR pickup sensor, and so the
LM2907/LM2917 must rely on triggering off of zero-crossings.
The data sheet tells you that a zero cross does not trigger anything: -
Y …
- 473k
1
vote
Zero crossing circuit
You have ground connections on both sides of the opto-isolator and this is significantly problematic for isolation reasons AND will cause half wave rectification of the signal and lead to your output …
- 473k
3
votes
Accepted
Why this ZCD not working?
When the input goes negative you are exceeding the input common-mode voltage range (as specified in the data sheet) and strange things will happen: -
In other words, your input is going below 0 volts …
- 473k