Home power socket hz tester

[Capernicus]

I wonder if this would work?

[golden_labels]

Attach the images, instead of hotlinking random files. In particular since you have used an address of Facebook’s CDN.
edit: for those, who can’t view the image, see the post below.

Depends on what you mean by “work”. The frequencies needed for the gimmick capacitor to be low enough impedance for LEDs to emit light are in dozens MHz range and above. If your goal is to use your home installation to determine if there is a radio transmitter nearby, then I will sarcastically say it hypothetically might work.

To determine if mains frequency is within specified range? To start with, that’s a high-pass filter.⁽¹⁾ To tell if something is in range you need two bounds to be checked. So, ignoring absolutely everything else, this couldn’t even hope to act as such a tester.

⁽¹⁾ That’s an RC circuit, which acts as a low-pass filter if, what is considered the signal, is voltage at the node between the elements. In your case the signal is current through the elements, which makes it a high-pass filter.

[IanB]

You have an Australian flag, so if you measured 60 Hz it would be very strange.

[Capernicus]

Ah yes I didn't know that, it looks like its 50 hz, not 60.  but that's what I need to find out.

Yes I dont the exact values involved, just plugging it in could be not enough, could be too much power.

1 picofarad would be a larger large reduction of the electricity at the 50hz.

I'm putting out 1 picofarad 50 times a second,  so that would be 50 picofarads worth a second,  so probably I bet the leds would be NOT on.

So u need a slightly bigger capacitor than that I would say.

[Circlotron]

100nF 250VAC X cap will give you about 7.5mA at 240V. Put a 1K surge rated resistor in series with the cap because without it if you apply power at the peak of the AC sine wave the LED will explode.

[Ian.M]

Although the forum would IMHO be a better place without his psuedo-electronics contributions,  please do not encourage the 'village idiot' to play with the AC mains supply.  The chances of him killing himself are far too high, and in doing so he may endanger others and will distress any friends/family.

If nothing else, please have sympathy for the first responders who will have to deal with his corpse.

One safe and appropriate way to measure mains line frequency is to use a bell transformer or other low voltage AC output transformer^*, with its input side wired up in compliance with local electrical code, then hook up its secondary to something capable of measuring frequency, e.g. a DMM with a frequency range, an oscilloscope, a frequency meter or even via a circuit to square up and limit the signal, to an interrupt capable pin on an Arduino or other MCU.

* *NOT* an electronic halogen lighting 'transformer' as they are actually AC output switched mode PSUs, with an output frequency in the tens to hundreds of KHz range!

[Capernicus]

100nF 250VAC X cap will give you about 7.5mA at 240V. Put a 1K surge rated resistor in series with the cap because without it if you apply power at the peak of the AC sine wave the LED will explode.

I doubt that, the cap works by itself.

[Circlotron]

100nF 250VAC X cap will give you about 7.5mA at 240V. Put a 1K surge rated resistor in series with the cap because without it if you apply power at the peak of the AC sine wave the LED will explode.

I doubt that, the cap works by itself.

If you doubt that, then you demonstrably don't have sufficient understanding of how things work, and in particular shouldn't be messing with AC mains connected circuits like you have posted. Like Ian.M says, get a low voltage transformer, preferably an AC output plug pack and use that. Your chances of living to see another day will be much greater.

[golden_labels]

I'm putting out 1 picofarad 50 times a second,  so that would be 50 picofarads worth a second,  so probably I bet the leds would be NOT on.

Producing more capacitors by applying higher frequencies would be an interesting production method, but it doesn’t work that way. Capacitance is a fixed⁽¹⁾ property of a capacitor.

Reactance of a capacitor at sinusoidal voltage with frequency f is: 1 / 2πfC.
Open a spreadsheet and, ignoring wire resistance and the diodes,⁽²⁾ calculate reactance for C = 1pF at various frequencies: from 10Hz to 10MHz.

I doubt that, the cap works by itself.

You have no way of telling that.

Although the forum would IMHO be a better place without his psuedo-electronics contributions,  please do not encourage the 'village idiot' to play with the AC mains supply.

One of the reasons I developed a habit of sometimes responding not for the benefit of an OP, but people who could potentially come across the thread later.

⁽¹⁾ It may change a bit with various parameters, including voltage, but not in a scale relevant to this topic.
⁽²⁾ Their effect is negligible in this case.

[John B]

100nF 250VAC X cap will give you about 7.5mA at 240V. Put a 1K surge rated resistor in series with the cap because without it if you apply power at the peak of the AC sine wave the LED will explode.

Nonsense, the green LEDs are shining with a perfectly healthy brown light.

[Capernicus]

100nF 250VAC X cap will give you about 7.5mA at 240V. Put a 1K surge rated resistor in series with the cap because without it if you apply power at the peak of the AC sine wave the LED will explode.

Nonsense, the green LEDs are shining with a perfectly healthy brown light.

why not just use a smaller cap.

[BeBuLamar]

I use my Fluke DMM. It works very well for this job measuring frequency of household AC power.

[madires]

With high efficiency LEDs 1nF could possibly work. However, encouraging people to do such a stupid thing really Hertz.

[retiredfeline]

And what you are going to do about it if the mains frequency is not 50 Hz? It's not under your control.

Clocks such as those in microwave ovens use the mains frequency to keep time. In the long run you will get 50 Hz.

[John B]

100nF 250VAC X cap will give you about 7.5mA at 240V. Put a 1K surge rated resistor in series with the cap because without it if you apply power at the peak of the AC sine wave the LED will explode.

Nonsense, the green LEDs are shining with a perfectly healthy brown light.

why not just use a smaller cap.

A cap by itself is no good as a current limiting device in this AC application. As circlotron is trying to point out, depending on when you apply power, the instantaneous voltage may be anything up to ~340V across the LEDs, only for a brief moment as the cap discharges, but plenty of time to destroy the LEDs.

*** This could also be a totally irrelevant line of discussion as I'm not sure what your circuit is trying to achieve, other than lighting LEDs in a flickery kind of way.

[Capernicus]

100nF 250VAC X cap will give you about 7.5mA at 240V. Put a 1K surge rated resistor in series with the cap because without it if you apply power at the peak of the AC sine wave the LED will explode.

Nonsense, the green LEDs are shining with a perfectly healthy brown light.

why not just use a smaller cap.

A cap by itself is no good as a current limiting device in this AC application. As circlotron is trying to point out, depending on when you apply power, the instantaneous voltage may be anything up to ~340V across the LEDs, only for a brief moment as the cap discharges, but plenty of time to destroy the LEDs.

*** This could also be a totally irrelevant line of discussion as I'm not sure what your circuit is trying to achieve, other than lighting LEDs in a flickery kind of way.

the cap isnt discharging in this circuit,  its just acting as a current blocker.

[BeBuLamar]

You can buy cheap Christmas light string that only power the LED with half the cycle and thus the LED would be flashing at the rate of the frequency of the AC power. However, those look continuously lighted with the naked eyes. So you wouldn't be able to tell the frequency any way.
I guess you want to make an application of using a capacitor to reduce current flow in an AC circuit. This isn't one of those applications.

[Capernicus]

excellent, thanx for telling me that!

so its actually 25hz per led in australia and u can actually just see it blink maybe!    its actually half the ac frequency, that u see on the led.

use 1nf, and see if it works.

[madires]

It's still 50Hz, 50 postives half-cycles and 50 negative half-cycles.

[Capernicus]

ah i was wrong...  oh well...

[magic]

Depends on what you mean by “work”. The frequencies needed for the gimmick capacitor to be low enough impedance for LEDs to emit light are in dozens MHz range and above. If your goal is to use your home installation to determine if there is a radio transmitter nearby, then I will sarcastically say it hypothetically might work.

You could do the math before trying to post concrete numbers, just sayin

You only need 50kHz to get 1mA from 15pF at 230V RMS.

You get 7µA from 100pF (~1m cable twisted together) at 50Hz. I recall reading on this very forum that some modern LEDs can be visible at such current. Conclusion: this may work, until you touch some exposed live conductor, that is

[james_s]

Although the forum would IMHO be a better place without his psuedo-electronics contributions,  please do not encourage the 'village idiot' to play with the AC mains supply.  The chances of him killing himself are far too high, and in doing so he may endanger others and will distress any friends/family.

If nothing else, please have sympathy for the first responders who will have to deal with his corpse.

Frankly the latter is really the only issue I'd have, and those guys deal with that stuff every day. I am not going to go out of my way to encourage someone to do something dangerous but I'm not one to try to protect every idiot from themselves either.

[Manul]

Human vision is really bad at perceiving frequencies, very limited badwidth too.

Hearing is many times better (for most people, who are not tone deaf). I can easily tell 50 Hz hum from 60 Hz hum. People with experience can tell engine rpm quite accurately from it's sound. You can sometimes even tell UART baud rates like 4800, 9600 from sound. Hearing is a useful instrument.

What I'm driving at is that a piezo in place of LED could practically be useful for telling you mains Hz. Maybe problem with piezo is that it would reproduce random higher harmonics much louder then the main frequency and may make matters slighly confusing to the ear. But hey, probably would still work. Flickering LED would certainly not.

[golden_labels]

You could do the math before trying to post concrete numbers, just sayin

You only need 50kHz to get 1mA from 15pF at 230V RMS.

My maths were in 10–20mA range.

[james_s]

Even something audible is probably not going to be useful. If you want to know the mains frequency in your country it's easy to just look it up. The actual frequency is going to vary only a very small percentage, it's not like there are going to be wild swings. Listen to the hum of any transformer or motor and you'll be hearing it.