Hello. I have a question, are there any LEDs or the like under alternating current (AC) from the transformer? The voltage I can get is 12V or lower. I don't want to do any DC rectifiers. BEST REGARDS

Hello You only insert the limiting resistance and problem solved. In the positive half of the sine the diode will be lit and in the negative half it will work in reverse mode (it will not light). This topic has been discussed many times on the forum, do a search. Regards

at 12V it is not necessary to look at the reverse voltage yet ... at 1k Ohm the diode will be lit (in the dark you will notice its blinking vaguely, it will be these half positive sine waves but that's right that the diodes have a small reverse voltage, so at higher voltages you need to be careful, but I don't see a problem with such a diode to turn it on at 230V, a very large R will shine, olo999 or maybe it's better to put the diode in series ... ?? what's the difference?

LEDs have a low value of the allowable reverse voltage of 3-5V. If you get 12V from the transformer, then you need to connect an anti-parallel rectifier diode or LED to the diode.

Thank you very much for your help, problem solved.

It's like connecting a 100V to 200V rectifier diode. In the reverse direction, a current of a few hundred nA flows through the LED, almost the entire 12V will be deposited on the diode, because with such a small current, the drop on the 1k resistor will be very small. I don't really understand what this connection is for?

then why can't I burn the LED at 25V AC?? and if the diodes are connected in series and the one has a much smaller reverse current, the other one will also automatically receive such a current

And how long did the diode work in such conditions? It's not about the current, it's about the reverse voltage. I guess the manufacturer gives this parameter for a reason.

I have a desk lamp for G4 halogen bulbs (12V), but the lamp gives 12V alternating current there and when using a LED bulb (18LED) you can see flickering, does this shorten the life of the bulb? and is there a simple way to rectify this current?

You can rectify the voltage with a bridge rectifier (the so-called Graetz bridge).

AC LEDs: Using 12V Transformer Without DC Rectifiers for Alternating Current LED Lights

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#1 2048319 02 Dec 2005 23:07

matmic matmic

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Post #1
2048319 02 Dec 2005 23:07

Hello.
I have a question, are there any LEDs or the like under alternating current (AC) from the transformer?
The voltage I can get is 12V or lower.
I don't want to do any DC rectifiers.
BEST REGARDS
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#2 2048336 02 Dec 2005 23:12

Aleksander_01 Aleksander_01

Level 43

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Post #2
2048336 02 Dec 2005 23:12

Hello
You only insert the limiting resistance and problem solved. In the positive half of the sine the diode will be lit and in the negative half it will work in reverse mode (it will not light). This topic has been discussed many times on the forum, do a search.
Regards
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#3 2048746 03 Dec 2005 07:18

Olo999 Olo999

Level 21
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Post #3
2048746 03 Dec 2005 07:18

Aleksander_01 wrote:
Hello
You only insert the limiting resistance and problem solved.

LEDs have a low value of the allowable reverse voltage of 3-5V. If you get 12V from the transformer, then you need to connect an anti-parallel rectifier diode or LED to the diode.

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#4 2048787 03 Dec 2005 08:43

DEMkO DEMkO

Level 20

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Post #4
2048787 03 Dec 2005 08:43

at 12V it is not necessary to look at the reverse voltage yet ... at 1k Ohm the diode will be lit (in the dark you will notice its blinking vaguely, it will be these half positive sine waves but that's right that the diodes have a small reverse voltage, so at higher voltages you need to be careful, but I don't see a problem with such a diode to turn it on at 230V, a very large R will shine, olo999 or maybe it's better to put the diode in series ... ?? what's the difference?
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#5 2048845 03 Dec 2005 09:27

matmic matmic

Level 14

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Post #5
2048845 03 Dec 2005 09:27

Thank you very much for your help, problem solved.
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#6 2052575 04 Dec 2005 14:17

Olo999 Olo999

Level 21

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Post #6
2052575 04 Dec 2005 14:17

DEMkO wrote:
at 12V it is not necessary to look at the reverse voltage yet... at 1k Ohm resistance

It's like connecting a 100V to 200V rectifier diode. In the reverse direction, a current of a few hundred nA flows through the LED, almost the entire 12V will be deposited on the diode, because with such a small current, the drop on the 1k resistor will be very small.

DEMkO wrote:
olo999 or maybe it's better to include a diode in series ... ?? what's the difference?

I don't really understand what this connection is for?
#7 2052893 04 Dec 2005 15:51

DEMkO DEMkO

Level 20

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Post #7
2052893 04 Dec 2005 15:51

then why can't I burn the LED at 25V AC??
and if the diodes are connected in series and the one has a much smaller reverse current, the other one will also automatically receive such a current
#8 2054062 04 Dec 2005 21:29

Olo999 Olo999

Level 21

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Post #8
2054062 04 Dec 2005 21:29

And how long did the diode work in such conditions? It's not about the current, it's about the reverse voltage. I guess the manufacturer gives this parameter for a reason.
#9 7713393 18 Feb 2010 14:38

toyo573 toyo573

Level 1

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Post #9
7713393 18 Feb 2010 14:38

I have a desk lamp for G4 halogen bulbs (12V), but the lamp gives 12V alternating current there and when using a LED bulb (18LED) you can see flickering, does this shorten the life of the bulb? and is there a simple way to rectify this current?
#10 7714264 18 Feb 2010 17:42

Olo999 Olo999

Level 21

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Post #10
7714264 18 Feb 2010 17:42

toyo573 wrote:
and is there a simple way to rectify this current?

You can rectify the voltage with a bridge rectifier (the so-called Graetz bridge).
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Topic summary

The discussion revolves around using AC LEDs with a 12V transformer without employing DC rectifiers. Participants suggest that while LEDs typically have a low reverse voltage tolerance (3-5V), they can be connected with limiting resistors to manage the AC input. Some responses highlight the potential for flickering when using LEDs in AC circuits, particularly with G4 halogen bulb replacements. A bridge rectifier (Graetz bridge) is mentioned as a solution for rectifying AC to DC, although the original poster prefers to avoid rectification. Concerns about the longevity of LEDs under these conditions and the implications of reverse voltage are also raised.
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AC LEDs: Using 12V Transformer Without DC Rectifiers for Alternating Current LED Lights

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