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Led lamp

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hi Ron,

I took the trouble to check the circuit, it supports your explanation [ and mine]

Eric
 
Eric Gibbs,

What spice model are you using for the LEDs? I don't have a good LED.

Most people think in voltage and not in current. A capacitor across the power line produces sign waves of current. (0.22uF) in out case

LEDs convert current into light not voltage into light.

Letting the current in the 0.22uF cap flow directly to the LEDs to be converted to light is a simple thing.
Converting the capacitor's current into voltage across the 22uF cap and then converting the caps voltage, through a non linear device, back to current to get light is hard to explain.
 
hi Ron,
Do you have the 'standard.dio'in your Lib/Cmp folder.??

If so, I could post the LED models I have, for you to copy into that folder.

E.
 
In fact the circuit will not work with 16 LEDs.
And that is another reason to not use the Zener.
I can see why a Zener keeps the voltage on the 22uF cap down if the LEDs should open up. OK ....but it limits what LEDs you can use.
I think the original idea was to use red LEDs where 16 1.5 volt parts work fine.
 
Eric,
Yes I do have standard.dio!
Thanks
ron

hi,
Copy and paste this text into your standard.dio

You will see them included in your diode F2 listing window.

E.

EDIT:
The NSSW LED's in that list are mostly White type.
 
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.The REAL purpose of the zener is to discharge the capacitor.
That's why I brought up the discussion in the first place. I thought that everyone had missed the purpose of the zener.

Sorry to say Colin, you have it wrong..

That is what R2, the 390K resistors job is.

BTW, this is a really crappy circuit design...I love transformerless Mains supplies when used safetly and correctly.....but this one IMHO is a no go.

Don't bother building it. It will not work properly.

@OP............Circuit designs taken off the Internet often are bad news. Unless of course the site is reputable. Like ETO. :):):)

No rubbish circuits here, just the facts.

Cheers,
tvtech
 
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Eric, thanks for the LEDs.

Sorry to say Colin, you have it wrong..
That is what R2, the 390K resistors job is.

TvTech is right about "discharge". I think Colin needs a different word, like 'reset' or '???'. The Zener is used as a diode to conduct the negative half of the current while the positive half goes through the LEDs. The positive and negative currents must balance (equal).

BTW, this is a really crappy circuit design...
Why don't you tell what you really feel? Tell us why.
 
tvtech: I am obviously talking about the zener discharging the capacitor during the operation of the circuit. The 390k is to "bleed" the capacitor when the circuit is removed from the mains.

I am amazed at how many technical ineptitudes have been displayed in this simple circuit. I have discussed these on my website, under "Spot the Mistake," P13.
 
Eric have you check LED current in the simulation ?

A few years ago I played with transformerless power supply.

And the max current was equal to

I = 6.8mA for Cx = 100nF ; Vin = 220V;

And for Cx = 220nF and Vin = 220V ; I =13mA.

But for half wave rectifier the current was equal 6.5mA.
To reach 20mA from half wave rectifier need increase the size of a Cx capacitor to 820nF
 
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hi Jony,
I did run a LED check in simulation its about 1.5mA, thats why I mentioned it in post #14.

Using the formula Xc= 1/[2*∏*50*C] its possible to work out the current for a 230Vrms supply.

One of the problems with the OPs circuit is the 48V zener, which holds the supply to the LED's to 48V, which is far too low for 16 White 3.5Vfwd LED's
 
Eric, thanks for the LEDs.

TvTech is right about "discharge". I think Colin needs a different word, like 'reset' or '???'. The Zener is used as a diode to conduct the negative half of the current while the positive half goes through the LEDs. The positive and negative currents must balance (equal).

Why don't you tell what you really feel? Tell us why.

Hi Ron

Here is why. I have in the last two years pushed the "envelope" as such with transformerless mains power supplies... There is a design I promised to show here when I initially joined here a while back. Design is rock solid and good to go.

Thing is, my original circuit just keeps getting better and better and has now become a serious shock hazard...

1. Original design was to power Eight white 20Ma 20 degree 15000 mcd LED's directly from 220VAC Mains, complete with backup battery and charger all smaller (or the same size) as a normal glass light bulb (like you use in your house). The circuitry and limited space needed double sided PCB's professionally made and extremely well designed.

PCB's and all LED's have passed all tests with flying colours. For more than Two years. Static discharge on the "head", where the LED's are mounted is a area I must fix...but easily done.

The Mains X2 cap does all the work in my design. It's a 2.2uf 275VAC rated cap. Maximum current (short circuit conditions) is 125 mA. Enough to kill if you are really clueless. No bare feet touching ground here...if you are a TV tech like me, you get a tingle and realize you must be VERY careful..

2. To the new level. A guy I know goes over to China. He brings back samples of COB. That means Chips On Board. Amazing stuff. Bright as all hell. Needs more current than my original design can supply. What do I do as a designer and developer of this baby?.....I push it to the limits..

First of all a test. I want to see how reliable X2 caps really are. These caps are able to survive almost anything. In my years as a tvtech and thousands of TV's, I have probably only seen about 3 or so fail.

One memorable Sunday morning...my friend and I decide to test this reliabilty and my little indestructible light. We ran it on 395VAC for about a Minute...like sixty seconds. No explosions no drama. The light works still..

Try that with a SMPS. You will first of all have a very hot (and possibly exploded) Main smoothing Cap. And dead SMPS.

3. So, with all this in mind, I decide to really push the envelope with transformerless power supplies:

LOL...this is REALLY LETHAL unless you know what you are doing...

The best my ORIGINAL circuit can handle is 5X 2.2MF 275VAC caps in parallel. Which equals around 600 Milliamps into a short circuit. Dont try this ever.

Unless you are able to deal with it safely. And know what you are doing.

Safe regards,
tvtech
 
hi Ron & tv,

The zener diode is not required in that circuit when using a 200nF or 330nF, it can be replaced with a 1N4007 diode.

This will allow an average LED current of 7mA with a 220nF and a 230Vac mains supply, with a 330nF approx 11mA.

I suspect the diode was originally added by the 'designer' to hold the positive half cycle and 22uF voltage at around 48v.
The zener method is used often to provide say a +5V for logic, a 5V6 zener is used, so at the other side of the 22uF connected diode would be ~+5V.

On the positive half cycle of the Line mains supply the current path is thru the upper 1N4007 and the LED series chain back to Neutral.

On the negative half cycle the lower 1N4007 is forward biassed and allows the current to flow from Neutral to Line.

The terms 'discharge and reset' are redundant in this circuit.

The 220nF at 50Hz has an Xc impedance of 14,468R, so the RMS current thru the capacitor is 16mA/2 [half cycle] ie ~8mA.

The 22uF helps reduce 25Hz LED flicker
 
Of course it should 50Hz, a careless error on my part, however that should not detract from the main body of my text.

Do you now understand the operation of the circuit.? if not please ask.
 
to erisgibbs,

Please explain how the 22u reduces the flicker.

Without the 22uF cap, the voltage across the LED's falls to zero during the negative half cycle of the mains, so the LED's are not lit during that period.

With the 22uF present during the negative half cycle, the 22uF supplies a lower holding current to the LED's so they do not go completely off.

The cap should be 220uF or 470u to give a more constant current thru the LED's.

These 3 images show the effect of the capacitor.
 
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Please explain: at what part of the cycle the electrolytic gets "all this extra energy" to deliver it to the LEDs.
 
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