LED on AC Mains

Important: Attempt only if proficient in working with AC Mains

A simple circuit diagram for a single LED on AC Mains 110v or 230 volts or even DC battery!!!

Step 1: Parts & Assembly

Parts:

1. An LED - 5mm or 10 mm of any colour
2. A diode, preferably 1N 4007
3. A resistor of 2 watts or higher rating, of value anywhere from 22 kilo ohms upto 100 kilo ohms.
4. A two pin male plug (hollow)

Lower resistor values will give more brightness and higher values will prolong LED life. So choose the tradeoff, depending on requirement.

Lower wattage of resistor like 1/2 watt or lower will not do and may burn since they are meant for 6v DC circuits, not for 220v AC Mains.

Assembly:

1. Connect black anode of diode to negative of the led.
2. connect the resistor to the positive of the LED.
3. Connect the free ends of the diode and resistor to the male pins.

Done. See the attached pic for clarity.

Another circuit with the diode connected "across" the LED is also attached. A bulb base adaptor is used instead of a male pin.

It should work on 110v AC as well as 220v AC Mains systems.

DC Feature:

It will also work on any battery!!

Once again, read "Important" first line, in case you missed it....

Step 2: Edit: April 2014

This instructable is becoming popular and common sense tells me that despite the "important" disclaimer about being proficient in working with AC Mains, many new people may also venture into making one.

So few guidelines as below:

Since only two components are used, both of them have to be robust to withstand AC Mains load.

1. The diode that i have used is 1N4007.

This 1N4007 diode is rated for 1000 volts and hence is robust to withstand both 110 v AC as well as 220 v AC Mains that different countries follow. Its also readily available, i guess.

2. The resistor 22 kilo ohm and above, should be rated for at least two watts or higher.

This will ensure that it will not burn due to continuous operation. A resistor is a current limiter. It limits the AC Mains current and converts it to heat and thereafter dissipates it.

HEAT is a problem, since a capacitor is not used. However, since a higher wattage resistor is used, it will not fail. Lower wattage resistors will fail and can cause damage.

Please be responsible and thoroughly test your work.

3. I could not use a capacitor ( non-polarised ceramic capacitor for AC Mains ) since space was a constraint inside the male pin.

If possible, use one:

--> 0.22 uF or 224 K, rated for 400 volts, if you are on 220 VAC Mains
--> 0.47 uF, rate for 250 volts, if you are on 110 VAC Mains.

See my other Instructables, for projects that use more LEDs and therefore a capacitor. See also various other circuits in this website as well as internet.

Step 3: My YouTube Videos:

https://www.youtube.com/user/MrPandyaketan

Comments

[jakesjacob65]

Hi, I need to connect LED strips to an electric fence. It's a very high voltage pulse which is generated
Could you suggest a circuit please.
Jakes

[RoderikT]

how do i connect the capacitor?

[pandyaketan]

There is no capacitor in my circuit. Please see again.

[RodenT1]

where should i connect the non polar capacitor??

[trevorwilliamsmith.]

if you want to connect a tiny light directly to the mains why not just use a neon bulb; simpler and safer e.g. http://docs-europe.electrocomponents.com/webdocs/1581/0900766b81581b67.pdf

[RiccardoR25]

That's a brilliant idea (no pun intended). I just ordered 20! Much safer, and much easier. Thanks.

[RiccardoR25]

Hi, You wrote:

>The resistor 22 kilo ohm and above, should be rated for at least two watts or higher.

I'm in 120v country. According to another YouTube video (not yours) a 1N4003 diode and a 47K ohm resistor will work (with 120V) for small "power-on" indicator light.

I don't need terribly bright light...and I want to avoid heat. I'm adding indicator lights to light switches, similar to the attached picture...only brighter.

Can you please respond back with your thoughts on resistor rating? Thank you.

[pandyaketan]

1/4 wattage you will definitely risk burning, since you are connecting to AC Mains. Also, 2 wattage or higher will not affect brightness. They are just for higher heat tolerance, during continuous use, like TV, Projector, etc...So for safety reasons use higher wattage, even with 47Kilo-ohms resistor with lower light intensity... hope it helps...

[RiccardoR25]

another clarification: The factory-made indicator light, as pictured uses a zener diode which I cannot read the small print on, and a 820K Ohm resistor, NOT a 82K Ohm resistor as I stated previously. My bad!

[RiccardoR25]

Clarifying the above question: The other YouTube video to which I refer above suggests using a 47K ohm resistor __at only 1/4 watt__! You're suggesting use of at least a 22K ohm resistor of at least 2 watts.

SO my questions are:

Is a 1/4 watt ok, or will I risk burning it up.
And if I go with at least 2 watts, will I reduce light output by 16x?

FWIW, the factory version uses a zener diode and a 82K ohms resistor, but it's not nearly bright enough.

[NikhilM70]

thanks for the nice piece of information. yes ! i have made...

Request to you kindly share same very easy circuit to power led smd strip roll but without transformers....

Actually i tried with capacitor.22uf(630v) Diode IN4007, resistor 4700(2w) and it worked but the light was dim not properly lit (I have used 24 led's of 2835 smd strip) .. please help...

Regards

nikhil

[pandyaketan]

Since an LED strip has LEDs in series, the circuit has to generate DC voltage. So try an AC Mains to DC for LED (diode bridge, full rectification), like in this circuit:

https://www.instructables.com/id/Worlds-best-LED-l...

reg

ketan

[AbhijithC2]

Two points :

1) You don't need an extra diode (1N4007) as mentioned, since the LED itself will do the rectification.

2) The Resistance should be 2 watts since the wattage drop across the resistor in that range, not because this is connected to AC. You can use a 1/4W resistor very well in ac if the current flow is limited further (by using higher value resistance). You can calculate the power drop across the resistor using the equation P = V^2/R = 230^2 / 22k = 2.4W. See that the power drop is more than 2W. To be on the safe side, use two resistors of 11K each and rated 2W each, in series, so that the power drop across each of them will be only 1.2W and hence lower than their rated dissipation.

[outwest01503]

You could also use two 44K resistors in parallel. Half the current (and thus half the power) will go through each resistor. It would also be smart to put a 20 or 50mA fuse in series in case a resistor fails and loses it value (in the smaller direction).

[jimdkc]

You do need the diode because an LED can only tolerate about 5-6 volts of reverse voltage.

[sun13zen]

I made a signup on instructables only to thank you. It was successful, but i used 56k/1w resistor. I've enclosed this circuit inside a mcb box as an indicator. thanks again.

[pandyaketan]

Thank you! Very kind of you!

You'll find many interesting projects here...!

[SalmanA81]

Hello there,
I have not found 2watt resistor of 22k ohm in my local stores. They have 22k ohm of 1watt and 100 ohm of 2watt.
Can I join them in series to make 2+1=3 watt?
**I have enough space to use capacitor. Should I use one?
I am new on these projects. Please reply.
Thanks.

[KrisBlueNZ]

Here is an electronics engineer's analysis of this instructable.

1. GENERAL

This design uses a half-wave rectifier to eliminate the negative half-cycles of the mains voltage, and a series resistor to limit the current. The brightness of the LED, and the power dissipated in the resistor, can both be calculated if you know the mains voltage and the value of the resistor. The formulas, written the way you would enter them on a calculator, are:

2. CURRENT AND POWER FORMULAS

I = V / R / 2.22
P = V * V / R / 4000

where:
I = average LED current, in milliamps;
V = mains voltage, in volts RMS (in most countries, either about 115 or about 230);
R = resistance of the resistor, in kilohms.

3. RESISTANCE FORMULAS

These formulas can be rearranged so you can calculate the right resistance for a given current or power dissipation:

R = V / I / 2.22
R = V * V / P / 4000

4. EXAMPLE CALCULATIONS

Using mains voltage = 115V and R = 6.8 kilohms:
I = 115 / 6.8 / 2.22 = 7.6 milliamps;
P = 115 * 115 / 6.8 / 4000 = 0.49 watts.

Using mains voltage = 230V and R = 27 kilohms:
I = 230 / 27 / 2.22 = 3.8 milliamps;
P = 230 * 230 / 27 / 4000 = 0.49 watts.

5. COMMENTS

(a) LEDs are typically operated at 10~20 mA (milliamps) so in both of these examples, you will not get particularly high brightness out of them. If possible, use LEDs with high efficiency, i.e. high light output for relatively low operating current.

(b) The resistor should be rated for at least twice the expected power dissipation. In these examples, use a resistor rated for at least one watt.

(c) You may have noticed that the power dissipation in the resistor is the same in both examples, but the 230V example has only half as much LED current as the 115V example. This is correct. It's a consequence of one of the laws of physics, and ye cannae change those (Cap'n)!

(d) Heating in the resistor is proportional to the power dissipated multiplied by the "thermal resistance" to the surrounding air. The thermal resistance, and therefore the temperature, can be reduced by (a) using a larger resistor with more surface area; (b) thermally coupling the resistor to something with more mass - for example, using a rectangular resistor and squeezing it between the two sides of the plug; (c) there may be other tricks I haven't thought of.

(e) The polarity of the diode and the LED must match. Connect the anode of the diode (that's the end opposite the stripe) to the cathode of the LED (that's the shorter lead).

(f) The version of this circuit with the diode connected across the LED, instead of in series with it, will work but the resistor will dissipate twice as much power as in the main circuit (the one with everything connected in series). The calculations are for the main circuit.

(g) There are various ways to improve the performance of this circuit but none of them are as compact as this design.

(h) Yes, the LED will flicker 60 or 50 times per second (depending on your mains frequency). This is not normally noticeable, but you will notice it if you turn your head quickly from side to side while watching it. You will also see this effect with a clock that has an LED display. When you look straight at it, you probably won't notice the flickering.

(j) Many blue and white LEDs are ESD-sensitive; that means they can be damaged by electrostatic charge from your body during handling. Try to get the manufacturer's data sheet for the device you're using, to see whether it's ESD-sensitive. If so, keep the leads shorted together with a paper clip or conductive foam until the circuit is fully assembled.

(k) If the LED is ESD-sensitive, it can actually be damaged by ESD after the circuit has been assembled and mounted in a mains plug. To protect the LED, connect a low-value capacitor across it before you remove the shorting clip or foam. For example, a 0.1 uF (microfarad), 25~50V ceramic capacitor. To save space you can use an SMT (surface-mount technology) MLCC (multi-layer ceramic capacitor) such as these ones from Digikey:
http://www.digikey.com/product-detail/en/C1206C104K5RACTU/399-1249-1-ND/411524 ("1206" size code)
http://www.digikey.com/product-detail/en/C2012X7R1H104K085AA/445-7534-1-ND/2733606 ("0805" size code - smaller).

(m) Connecting this circuit to your mains supply may be illegal, depending on your country's regulations.

(n) Every point in this circuit must be considered live and dangerous. You must do everything possible to prevent any person from coming into contact with any point in the circuit. Some examples I suggest: (a) replace the screw that holds the socket together with a nylon screw and nut; (b) recess the base of the LED into the plug and/or surround it with glue to prevent any possible access to the LED wires in the area between the LED base and the plug.

[GopalaK12]

in current and power formula it was divided by 4000. What and why this division by 4000? Can you please explain?