[SOLVED] Led on 220v ac check my circuit

[btahir90]

there is 220v ac supply and 2 striing of lots of leds.
1.please tell me will this circuit works or not?
2.Is there any need of rectifier for dc to ac? as i think in one wave one string will conduct and in other wave other cylcle should conduct
3.what if i did not wanted to use resistor? can incresing no of series led s will limit current.

reply?

 

[Sloth]

1. It might burn the LEDs (200 mA). Use a 10k resistor instead of 1k and it will work (20 mA). The resistor need to withstand 200 Watts though

2. Your circuit will flicker slightly (even if it's said that human eye only detects 20 Hz flicker with 50% duty cycle). With a rectifier bridge and proper bypass caps you can get rid of the flicker.

3. It's not a proper way, since LED voltages vary. Might be dangerous.


E: added current values

 

[kabeer02]

I will advice you to use DC instead of AC , using AC you will notice some flikering and the intensity of the led will reduce.

 

[BradtheRad]

Capacitive drop is an efficient method to drive led's from mains AC.

It uses reactance to drop volts. Hence it does not generate heat as a resistive drop would.

A value of 220 nF is about right for 220 VAC. The led's can be any color and any number (within reason).

The resistor is included to limit current surge at powerup.

If one led goes open circuit, the other led string will be exposed to 320 V peak. This could exceed their combined reverse threshold and destroy more led's. To prevent this, add a 400V diode to each led string.

Here is a screenshot of my simulation (done with www.falstad.com/circuit).

 

[btahir90]

if i use bridge rectifier and a capacitor and 2 parallel arrays of 75 led's in series then what?
i would still require a resistor?
i mean when i connect led to 3v dc i never use a resistor

 

[tpetar]

View attachment 83747


there is 220v ac supply and 2 striing of lots of leds.
1.please tell me will this circuit works or not?
2.Is there any need of rectifier for dc to ac? as i think in one wave one string will conduct and in other wave other cylcle should conduct
3.what if i did not wanted to use resistor? can incresing no of series led s will limit current.

reply?

Use capacitor and resistor in parallel to lower high voltage to range 60V-30V, then rectify with Graetz bridge.

Examples:






Your design is very dangerous and you will often have dead diodes!
Also take in mind that mains voltage is not always 220V, voltage floating in some range, can be 240V or more or less, this depends from many things.

 

[BradtheRad]

if i use bridge rectifier and a capacitor and 2 parallel arrays of 75 led's in series then what?
i would still require a resistor?

With capacitive drop you can string dozens of led's together and hook them up to the mains AC. Just be careful not to let them be exposed to overmuch current.

It's best to put a resistor inline, as a safeguard. It really ought to be a higher ohm value than shown in my schematic above. More like 4700 ohms, with a watt rating of 3 or 4 or 5 W.

And if you arrange the led strings in parallel facing the same direction, then you need an equalizing resistor inline with each string. The purpose is to prevent any string from 'hogging' current.

i mean when i connect led to 3v dc i never use a resistor

Evidently your 3V supply has some internal resistance, to permit you to do this. Or else you have an led which is manufactured to tolerate this.

Measure the volt level on the led while it is hooked up. Measure current through it.

There was a time when led's were commonly red, took 1.8 V, and 20mA max.

 

[btahir90]

thank you very much to all.