Cheap Trick to Connect a Regular LED to 120 VAC?

I agree GA & a good site for reference lots of information

GA for a good answer though answer #1 also is correct but may not be for the poster.

In cheaper musical-door bells [not in using the Isolating low-voltage transformer style] a cap & a Diode idea is used as well.

I am not familiar with different types of LED. but I have worked with two types, one was glowing on 1.5 V DC and other on 2,5 to 3 V DC.

What type of LED, we can use in this circuit? Are some LEDs draw more current and some draw less?

Yes to your question.

Draws, depending on concept, size, color and light output a different current feed. In the first designs you can try your led with a higher value resistor and/or lower value capacitor. I live in a museum and used polyester capacitors. The dimmer you use the led, the longer it will work.

Simpler still.....

You could go with a 2W resistor due to the 50% duty cycle.

Not efficient but cheap.

Not 50% duty cycle. It is 100% due to DC supply.

Not DC.

That's the peak voltage model for half wave rectified through the diode (LED)

Actually less than 50%, but I couldn't be shagged working out the RMS voltage of a half wave.

it's recommended to consider it 70.711% in calculations ??? the effective value for AC's I & U ... apx.quote "the amplitude value for AC must be √2 of that of the DC for the resistor to emit the same amount of heat or use the same kWh"

It appears you have a DC input not AC.

Tony

I didn't draw that, it came that way from the site with the voltage drop calculator. (click on the picture)

You have to consider the peak voltage of the waveform to get the peak voltage drop requirement. Right?

120VAC RMS is about 170V peak.

I think that's correct, and because it's a diode, we don't worry about it being AC? But does say: "With a supply voltage of more than 24V, you'll dissipate excessive heat in a current-limiting resistor."

It's certainly cheap, but I think I'd be a bit nervous, but I don't have sufficient knowledge to comment intelligently. We are 240v in Australia, do others think it is a viable solution.

I just tried an LED with 40v DC (max on my power supply) and a 2.2k 0.5w (they specify 2w) resistor (only one I had) and after about 30s it started to warm up.

Tony

Yeh, resistors do that.

Properly locating components is part of the craft. keep it away from things that don't like getting hot.

A higher powered resistor will still get hot, it won't fuse is all.

On AC without a series diode full supply voltage will appear across LED and it is not rated for that much reverse voltage which is of the order of less than 15V. See the data for an LED.

Regards

Good for DC only.

This kind of low cost solution has been researched by many and will be done in future too. Cheap capacitive and diode solutions have been suggested on this blog. I will be very happy - that after just few days / weeks- I I will find you coming back to CR4 website and saying LEDs are lousy, they get dimmed and you need a torch to find where your LED is glowing. Kindly look up discussions of LED failures on CR4 website before. I will be glad that one more person would have been added to the list of anti-LED users shortly.

There are and there will never be any cheap solution to driving LED- other than constant current source - if you want really want reliable circuit. Watch how your specs will keep changing.

"Curiosity has its own reason for existence" -- Albert Einstein - today you are first stage of Curiosity.

Connecting 120V-AC OR 240V-AC is the best solution for general & commercial use of LEDs. please note that there is intermediate equipment that take care of function of constant current( around 300m-Amps) source that required by LEDs.

Scrap the LED and use a neon bulb

OP wants to use a LED for some reason. Neonindicator is the right choice (maybe).

An incandescent lamp would work too and get as about as hot as the dropping resistor for the LED.

Here's a thought...put a 5W/120V incandescent lamp in series with the LED. Solved!!

"Here's a thought...put a 5W/120V incandescent lamp in series with the LED. Solved!!"

It is not that simple. 5W/120V incandescent lamp will consume 41 ma of current. It will overdrive the LED, there by reduce its life. Since this configuration has 50% duty cycle, the brightness will be halved consequently.

A good idea. But colour-spectrum and flickering? Some people are sensitive much higher than 120/s flickers.

LED has a broad range of selection while very limited in neon bulbs.

Not much colour choice at that voltage but flicker?

1. resistors and inductive coils loose their watts as heat
2. diodes and constant R alternate transistors follow 1.
3. transformers also heat up due varying EMF
4. automated FET switches (step down converters) looks 1-st good joice to me ()never used any
5. ??? if you have 2x24 5V LEDS @ 120VAC side and array of Solar batteries in DC side you receive less than 50% efficiency power converter (likely not a good choice ...)
6. ?? how efficient are modern vacum tube #-odes (maybe there's some modern materials for cathodes doesnot meed to heat up to emit electrons) ??? a FET alternate (i gess the vacuum is better conductor than ... a semiconductor)

I have gone into great detail on the practical application of the capacitor voltage divider circuit previously

Link

It can be done but safety (both electrical and fire) is a concern for a DIY application, so be careful if you wish to use it or something similar.

It had to be a GA for such a well written comment as well as addressing the safety concerns.......I can also see too many areas of danger to the user if something goes wrong.....

I personally would not do it as I am still an old fashioned believer in Neons as a safer high voltage indicator.....also not without certain dangers, but still significantly safer than LEDs....

If I was determined to use a LED, I think that I would try picking up some voltage from the line wire using a small coil, so basically a transformer type of application......never actually tried it, but I like the idea of no direct connection personally.....

Check Energetic forum Joule Ringer Thread and YT

Lots of ckts to choose from lighting multiple 220 V ac led lamps from 12 v dc battery

converted to 220 0r 110 v ac

Try an item like a 1091M?-125VAC, ? 1=Red, 5=Green, 7=Yellow. This is an off the shelf item and hooks directly to 120 VAC it no issues. Current for this device a bit over 4 mils

We have been using LEDs Lighting since 2008 by using supply voltage as 220V-AC. In one of the projects, A to Z all LED lightings are only that includes RGB for color changing using central command station. we are now using out side lighting such as Facade, uptree lighting, street lighting including indoor full lighting only LEDs as they have long life, low power consumptions and small wire sizes in cross section. All these LED lightings need following:

1. A constant DC current driver of 12DC, 24DC, 48DC with in put power is 220V-AC

2. If more than one LEDs are required that needs series connection only.

3. LED needs to maintain only 300 to 350m Amps and 1.5V-DC drop across it what ever DC voltage you apply.

4. Its PN junction temperature shall not exceed to 120C during operation.

Now very soon Air port RUN way lighting is going to replaced by LED lighting.

Having said above that, I do not understand that we are talking about zenor diode, capacitor & resistor connection. all these are for what?. It is clear that a LED street light of 125Watt consisted of 500LEDs inside the lighting fixture but not one LED. So how it can be implemented above theory of Zenor diode, capacitor and Resistor in street lighting fixture?

Once again I say that cheapest and easiest power supply for LED lightings are 120V-AC, 220 OR 240V-AC for practical use.

I think that you have misunderstood what the OP, wants.......

I want to drill some 5mm holes in a 12" PVC (thickness 1/4") colomn, close to the dockpile (read in the dockpile). The reason for doing this is that on that dock a boat is moored, and a long distance IR camera is focused on it. (distance = about 100 Yards).

The LEDs from the camera lost a lot of intensity over 2 years and I want to "light" the boat more locally (closer to the boat) with a bunch of regular IR LEDs that fit in those drilled holes.

I have 120 V AC there and like to have a circuit that switches on a series of these Leds when it is getting dark.

Has any a practical idea? I can drill plenty of holes. Thanks

OK now we have a fuller picture.

Hazardous location mate. You don't want a 'cheap solution" you want a proper solution.

Install a 120VAC to 5VDC power supply brick (these are relatively cheap) inside a suitable enclosure in a safe location and run your LEDS off that.

Use a regular light sensing switch for the power supply.

Alternatively install an IR illuminator at your camera location.

How about solar and batteries?

I think what you need is some thing like a water proof case to put a power supply like this one here into, size will depend on how many LED's you want to use. Then you could take your pick of any of the LED's like these. If you are using the smaller LED's get dropping resistors some of them are supplied with the resistors for 12 volt. If you are using the 1w LED's you need to get the appropriate drivers to run them from 12v. To control when they turn on you could get a light sensor switch to either run on 12 volt or mains voltage like these here.

I would think if you already have a weather proof area to mount the power supply into it would cost under $30 for the power supply light sensor & a large quantity of the LED's, then add the wire to run to where you want the LED's. It's safer to set up, you only need to worry about 12 volt at the lights.

Because the lights don't draw much power you don't need any thing better than speaker wire, tinned would be better to stop corrosion but sealing the ends of the wire after soldering with paint or something will help.