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66 LED use 220v AC ?

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DerStrom8

Super Moderator
The resistor does not limit the voltage. It limits the current.

It is never a good idea to connect LEDs directly to mains. There are a lot of things that can go wrong, so current limiting and circuit protection is needed. I would strongly advise against connecting 66 LEDs to 220v AC.
 

audioguru

Well-Known Member
Most Helpful Member
I have Christmas tree lights that have many LEDs in series. They are inexpensive but are not bright. They seem to flicker at the mains frequency.

Nobody makes a 3.6V LED. It might be 3.4V or 3.8V or any voltage in between. Many in series might have an average of 3.6V but they all might be 3.4V or 3.8V or anywhere in between.

220VAC has a peak voltage of 311V with one polarity then 311V with the other polarity. The polarity alternates.
An LED has a maximum allowed reverse voltage of 5V.

If you connect 66 LEDs in series then the peak reverse voltage of 311V will destroy them. The peak forward voltage of 311V will also destroy them.

But if you connect two LEDs back-to-back and with one reversed then one lights and protects the other on each half-cycle of the AC. Connect 86 pairs in series.
 

DerStrom8

Super Moderator
Nobody makes a 3.6V LED. It might be 3.4V or 3.8V or any voltage in between.

Um........ You might want to read through that again :D
 

colin55

Well-Known Member
It is best to turn the 220v into DC:
**broken link removed**

DC CONNECTION
To prevent "flickering' or "strobing," the LEDs must be driven with DC. This requires a BRIDGE.
The 0.22u will deliver 15mA when one LED is connected to the output. As additional LEDs are connected, the current gradually reduces to zero with 100 LEDs.
40 LEDs will be provided with:
345 - 145 = 200v = 200/345 x 15 = 8.6mA
 

Diver300

Well-Known Member
Most Helpful Member
The reduction in current is more complicated than that to calculate, because you have to take into account the amount of time that the supply voltage is above the LED voltage. The current will be reduced somewhat by having more LEDs, and you probably don't need to know the current very accurately.

The LEDs will still flicker at 100 Hz with that circuit. If you have 66 LED, with a total voltage of 240 V, the 220 V RMS sinewave will only be more than 240 V for about 45 % of the time, so the lights will be off for more that half the time.

If you put a 100 uF 400 V capacitor across the output of the bridge rectifier, there will be no visible flicker. You should also add a resistor of around 100 ohms in series with the capacitor to limit inrush current when you first turn on.

You should also put a resistor of around 1M in parallel with each capacitor to discharge them after you unplug, so that the capacitors don't store dangerous voltages for hours after being turned off.
 

Gayan Soyza

Active Member
I'm with Diver

you can add a capacitor output of the bridge that will vanish the flicker it will work from 47uF.

I'll also add a 1Mohm resistor across the capacitor to discharge it.

I'll also add a series resistor like 47Ohms near one of a power rail to bypass inrush currents.
 
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