# Otaku's LED Tea Light Hack - Updated!



## Devils Chariot

Special thanks to Otaku for digging up the how to for this. In gratitude and with his permission I am posting his PDF as a thread.

Tea Light Hacking Instructions by Otaku

Parts you'll need:
_Ultrabright LED 1 each (I used a white LED)
Diffuser for LED (you'll probably need this as many ultrabright LEDs are beam-type and don't spread light very well)
Small gauge wire
4AA battery holder (use the flat type, it will be easier to mount to a lantern)_

1. Remove the battery tab from the tea light and turn it on to make sure it works.
Use a razor blade or X-acto knife to cut away the silicone "flame" molding.
Your tea light may require dis-assembly to get to the "flame" cover.










2. Cut off the original LED leaving as much of the leads as possible exposed.
Solder the new LED to the leads. Check the polarity before doing this so you only have to do it once.
You can do this by touching the new LED legs to the cut leads and seeing when it lights up.










3. Remove the battery cover and the batteries. Solder in the small gauge wires as shown.
The red wire is the positive lead. Note that your battery arrangement may be different,
just be sure you know what the polarity is after you attach the wires.










4. Cut some small notches in the battery cover to accommodate the lead
wires and replace the cover. Again, your tea light may be different from this one.










5. Connect the battery leads to the 4AA pack and turn on the light.
If it doesn't come on reverse the wires to the battery pack.

step 6. continued below.


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## Devils Chariot

*continued...*










6. I got these diffusers at Michael's for ~$1. Choose the diffuser color you want to use and drill
a 5mm (~.200") hole into the bottom. If you use the diffusers shown in the picture, pull of the
little rubber "threaded" cap and cut off the small knob before drilling. It helps a bit to sand the
base flat - it keeps the drill point from skipping around. Place it on the LED with a bit of glue.
You can do this before (as shown) or after soldering the LED.










Done!

7. Recommendations:

Cover the white plastic shell of the tea light with black tape or paint.
Also do this to the bottom of the LED, if you used a white one.
There is some light leakage through the bottom of the LED that will wash out the colored diffuser a bit.


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## HalloweenRick

Nice Job!


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## Just Whisper

Okay, I am going to sound really stupid now. I don't get the point of this hack. I think I missed something. Why don't you just wire the led with a resistor to the battery pack? Why do you need the tea light fixture? Sorry to be so dumb...


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## Otaku

Just Whisper said:


> Okay, I am going to sound really stupid now. I don't get the point of this hack. I think I missed something. Why don't you just wire the led with a resistor to the battery pack? Why do you need the tea light fixture? Sorry to be so dumb...


There's a little flicker circuit in the tea light. Keeping everything in the tea light case just makes it easier to handle.


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## Just Whisper

Oh yeah. I knew that. de de de!! Thanks for explaining. I knew I'd feel dumb when the blatantly obvious was pointed out to me. LOL


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## electr0n

Otaku, thanks for the hack. This is something that will come in handy for a lot of people. I see the flicker tea lights everywhere now so they're easy to come by.


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## MotelSixx

Add that to my To-do list!!!
great work


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## Revenant

Schweeet. I'm definitely using that. Danke, mein hackmeister!!!


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## Devils Chariot

Hey Otaku,

I want to use a 9 volt battery to power my circuit. At 9 volts the flicker is becoming less erratic. How would I knock down the current (?) to get something more like 6 volts or even 3 volts? (the batteries that come with the lights). I would assume some resistor, but I don't know how to calculate what resistor would - 3 volts.


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## Otaku

Here's a good LED calculator:

http://led.linear1.org/1led.wiz

Just type in the required values and you're good to go.


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## july1962

*tea light hack*

Another dumb question...what is the reason for replacing the LED bulb?


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## Devils Chariot

the led supplied is not very bright. By replacing it with an ultra-bright led, you get a much brighter realistic effect.


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## july1962

OIC. Actually a flame on a little tea light like that wouldn't be all that bright. I set about 50 of these out last year, without the hack, and I thought they were plenty bright. What I'd like to be able to do, is run a series of them together with a dc wall wart.


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## Otaku

If you wire them in series to the wart, you'll run out of voltage pretty quickly. If you wire in parallel you can place a lot more of them - just be sure you have the amps to run them all - but the wiring harness will get kind of hairy. If you don't mind them all flickering at the same rate, here's a circuit that you might be able to use. It's about halfway down this page:

http://www.hauntforum.com/showthread.php?t=17685&page=2


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## july1962

I'm not very good at this stuff, I'm not sure what "wire in a parallel" means. Does that mean half on one side and half on the other? I'm only talking about 10 at a time.


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## Terrormaster

Simply put, parallel is wiring the lights positive to positive and negative to negative... In series means connect the positive of one light to the negative of the next. Think Conga Line (parallel) and a group holding hands in a circle (series).


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## Otaku

You're close. It means that all of the "+" tea light connections would go the "+" side of the wart, and all "-" connections to the "-" side. That way all of the lights get the voltage they need, and you only need to make sure that the wart has enough amperage to handle the load. Estimating the current draw of the tea light at ~25mA, a 500mA wart would handle ~20 lights. If your lights use 3 button-cell batteries, then you need a wart with 4.5 - 5VDC output. Check the thrift stores for cell phone chargers - they're usually 5VDC and run ~800mA or more.
This 2-pin connector assembly will make the wiring a little easier.

http://www.allelectronics.com/make-a-store/item/CON-232/2-PIN-CONNECTOR-W/HEADER-.156/-/1.html

Solder the wires to the battery pads in the tea light, keeping the red wire to "+". Then wire the header the same way to the wart. This helps wire handling and keeps the polarity straight.


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## july1962

My tea lights use one CR2032 flat lithium battery each. Could I use one 9V dc 1 amp wall wart and run the 10 tealights?


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## Otaku

The CR2032 is 3VDC, which is what a single light needs to run. Wiring lights in series would allow you to run only three lights on the 9VDC wart. The tea light flicker circuits are pretty robust - I've overdriven them many times, like running a 4.5VDC light on 6 and even 9 volts once as a test. The LED lit; the circuit wouldn't flicker at 9 volts but worked fine at 6VDC. If you want to use a wart, I recommend using a 5VDC, minimum 1A like this one:

http://www.allelectronics.com/make-a-store/item/PS-537/5VDC-3.7A-SWITCHING-POWER-SUPPLY/-/1.html

I have several of these warts. They're lightweight, cheap and put out a solid 5VDC. At 3.7A you could run hecka tea lights when wired in parallel.

Another option - use a 2 D cell battery holder wired in parallel. D cells last a long time and the 2 pack gives you the 3VDC you need. R-S has 'em cheap:

http://www.radioshack.com/product/index.jsp?productId=2062241

The tea lights, even 10 of them, should last a long time, and you get to keep the portability, too.


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## july1962

What kind of wire should I use for this? I've been searching all over for the thin 2 conductor wire that is similar to what's on the wall warts, but I can't find it anywhere. Of course I want black and pretty pliable.


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## july1962

Otaku said:


> You're close. It means that all of the "+" tea light connections would go the "+" side of the wart, and all "-" connections to the "-" side. That way all of the lights get the voltage they need, and you only need to make sure that the wart has enough amperage to handle the load. Estimating the current draw of the tea light at ~25mA, a 500mA wart would handle ~20 lights. If your lights use 3 button-cell batteries, then you need a wart with 4.5 - 5VDC output. Check the thrift stores for cell phone chargers - they're usually 5VDC and run ~800mA or more.
> This 2-pin connector assembly will make the wiring a little easier.
> 
> http://www.allelectronics.com/make-a-store/item/CON-232/2-PIN-CONNECTOR-W/HEADER-.156/-/1.html
> 
> Solder the wires to the battery pads in the tea light, keeping the red wire to "+". Then wire the header the same way to the wart. This helps wire handling and keeps the polarity straight.


I ran this by an electronics friend of mine and he wrote back:

"Putting 3 tea lights in series MAY work (but it may not), it depends on the circuit of how they are made to 'flicker' - each one wants 3 volts to operate so 3 + 3 + 3 = 9 volts. Try it if you can and see if it works. If it does then you could bunch the tea-lights into strings of three and the run a number of strings of three off the one wall wart."

What do you think?


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## Otaku

july1962 said:


> I ran this by an electronics friend of mine and he wrote back:
> 
> "Putting 3 tea lights in series MAY work (but it may not), it depends on the circuit of how they are made to 'flicker' - each one wants 3 volts to operate so 3 + 3 + 3 = 9 volts. Try it if you can and see if it works. If it does then you could bunch the tea-lights into strings of three and the run a number of strings of three off the one wall wart."
> 
> What do you think?


Yes, that should work. You're essentially running sets of 9VDC loads in parallel from the 9VDC wart.


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## july1962

So I wired together three tea lights and hooked it to a 9v-1a wall wart. They lit for a second and then blew out. What now?


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## Otaku

july1962,
Were the tea lights wired in parallel or series? Parallel wiring will send 9VDC to each light (bad); series wiring will spread the load across all lights in the circuit (3 X ~3VDC). Do you have a pic showing how you wired the lights? One other thing - is the wart regulated? If not, it can run at significantly higher voltages until it's internal circuitry stabilizes, resulting in an initial power surge.


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## Devils Chariot

I found in my test that these tealights just pass on the voltage to the led:










You need to put a resistor between the led and the tealight circuit. This might be too much hacking for you though. I have run three of these off a 5v wallwart, and when I measure the voltage coming off the circuit to the led it is almost the same as the voltage going into the candle. Same result when I used a 9v battery. And as stated before the higher the voltage, the less flicker. the problem here is that 3v+3v+3v is what you need to run the circuits inside the candle, but since they pass on the voltage, you need to add a resistor between the led and circuit to wire in series.

It might work to put resistor between the wall wart and the candle, but then you have to wire in parallel again.

EDIT: I might not be 100% right so listen to whatever Otaku sez


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## july1962

Otaku said:


> july1962,
> Were the tea lights wired in parallel or series? Parallel wiring will send 9VDC to each light (bad); series wiring will spread the load across all lights in the circuit (3 X ~3VDC). Do you have a pic showing how you wired the lights? One other thing - is the wart regulated? If not, it can run at significantly higher voltages until it's internal circuitry stabilizes, resulting in an initial power surge.


OK, I'm getting confused. You told me originally, "If you wire them in series to the wart, you'll run out of voltage pretty quickly. If you wire in parallel you can place a lot more of them - just be sure you have the amps to run them all."

So I wired them in parallel, like you said. Now you're saying parallel wiring is bad. For instance, I ran a green wire to all the same sides of the tea lights and then a red wire to all the other sides...that's parallel, right?

I don't know how to tell if the wall wart is regulated. It says on it:

Class 2 transformer
Input: 120 volt AC 60 hz 16W
Output: 9V DC 1A


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## july1962

I can probably wire in a resistor (suggestion on the actual resistor?), I've made my own LED spots. But I'm not sure where you mean to put the resistor...."between the LED and the tealight circuit?" Do you mean a circuit on the tealight or just the circuit of 3 tealights wired together? I don't see any kind of circuit on the tealight itself. Here's what I'm using:


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## Devils Chariot

you'll need a voltimeter to measure which is the positive lead to the led, but I mean put a resistor between the led and the little circuit in the tealight.

I'll leave you to Otaku, he is the master, I am but a student.


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## Otaku

july1962 said:


> OK, I'm getting confused. You told me originally, "If you wire them in series to the wart, you'll run out of voltage pretty quickly. If you wire in parallel you can place a lot more of them - just be sure you have the amps to run them all."


Please read the previous posts regarding the voltage of the wart. If wired in parallel, this means that each light is getting the full voltage that the wart is putting out. Using a 3 - 5VDC wart works for single-light parallel wiring, as I mentioned in a previous post. If you want to use a 9VDC wart, you have to wire the lights in series or they will get fried. If you wired this latest test in parallel, with only one light in each "string", that's why they blew out.
You can combine parallel and series wiring schemes with your 9VDC wart. You would wire three lights in series to one another which represents a load of ~9VDC. Make as many of these 3-light strings as you need; if we assume a current load of ~20mA per light this could be as many as 50 lights, or about 16 sets of three series-wired lights. Again, do you have a pic of how you wired the lights that blew out?

Edit: Here's a quick drawing of how the lights would be wired. This shows two series-wired strings of three lights each, attached in parallel to the wart. Each string is a load of ~9VDC, ~60mA.


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## july1962

I guess I'm blind...I don't see a "little circuit" in the tealight. I see the bulb which has two wires coming out that are soldered to two battery terminals.



Devils Chariot said:


> you'll need a voltimeter to measure which is the positive lead to the led, but I mean put a resistor between the led and the little circuit in the tealight.
> 
> I'll leave you to Otaku, he is the master, I am but a student.


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## Otaku

The circuit board is only there if you have flickering lights.


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## july1962

Otaku said:


> The circuit board is only there if you have flickering lights.


The do flicker. It must be inside the bulb.


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## Otaku

july1962 said:


> The do flicker. It must be inside the bulb.


Interesting! I've never seen ones that flicker without a circuit board. Did you check out the circuit drawing I posted?


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## coolbotz

If the flicker circuit is in the led itself you can series more leds in with the original and raise the voltage to 5 or 6 volts and all leds will flicker at the same time. This is the way the tealights from the Dollar Tree operate that I bought. The flicker led also has current limiting circuitry on die with the led.


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## Otaku

Cool. I assume that this type of LED is different than the standard blinker? Never seen them sold anywhere, but a very useful item.


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## coolbotz

Yeah, I was impressed with these tealights. 2 for a buck. The flicker effect was as good as I've seen. I've used the kind with the separate flicker circuitry also. I've been working on flicker effects with microcontrollers for years, but I can't touch the cost effectiveness of these. Parallel 3 of these with one CR2032 battery, add hot melt glue to create a flame shape and you have a very good jack-o-lantern candle (with shadows). The flicker pattern is unique to each led.


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## july1962

OK, with the help of my electronics friend in Australia, I've got this figured out. BTW, these are the bulk tealights from Costco. They don't flicker in unison, they have a very random flicker.

So from the 9V/1A wall wart, I ran the positive to 2-100 resistors and that to the positive terminal on the tealight. Then the negative from the wall wart to the negative on the tealight. I have now hooked up 6 tealights and they all have the same brightness as the battery operated one. He said I could hook up an almost endless amount of tealights using this method. Here's a photo. The tealight in the center is the battery operated one.


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## Devils Chariot

I'll have to get some of those tea lights!


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## Otaku

Nice! Those lights look good- time for a Costco run. Glad you got it worked out.


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## MBrennan

Is there a specific type of LED that you are using? I've seen other threads using spot vs. something else.


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## july1962

This thread was about already made tealite candles, the LED's are already built in.


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## Devils Chariot

actually this thread was about replacing the led that came with the candles, but it has since expanded into a how-to on wring in series and paralell. 

The tutorial calls for an ultra bright leds, almost all of which have a spot light effect. you will need a diffuser, like the plastic flame that come with the light or a replacement one like the one mentioned at the beginning of this thread in the how-to.


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## july1962

You're absolutely right, my apologies.


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## MBrennan

Thanks for the information. Might try and make a bunch of these, power them from a transformer, and put them in lanterns around the yard.


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## hpropman

cool post great info


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## Death Wraith

This thread is great because I just came up from my work bench trying to figure out how to wire up some tea lights to a wal-wart and found this! Cool! MY question is: my wal-wart is 3.7v and my tea lights are 3v. I wired one up and it lit and was a bit brighter than with a battery ( I'm using the standard built-in LED) I assume that running these at a little higher voltage (wired in parallel) will put more strain on the LED and shorten it's life. But how much shorter? Do you think it will last for 20 to 30 hours, which is about the length of our haunt over a 6 day period.


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## Otaku

I've measured the voltage across a tealight LED using a 4AA pack and found that it varies between ~2.6 and ~3.5VDC. The original batteries were three 1.5 volt button cells (4.5VDC) and gave the same readings. The current limiting resistor seems to hold the voltage to the range that produces the flicker effect. If you increase the voltage to say, 9VDC, you'll blow the resistor and the flicker circuitry. I use 4AA packs on tealights in lanterns and never had a LED fail. Just increasing the voltage won't give you much in the way of a brighter light - to get that you need to change the LED.


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## corey872

Sounds like some people are running into what is being termed "Type 2" LED tea lights. These are the latest version where the flicker is actually built into the LED. The best way I have found to use these for extra brightness is to have the flicker LED drive the base of a suitable transistor, then let the transistor drive the high output LED's. You need:

1 tealight with flickering LED
1 2N2222 transistor or equivalent (Radioshack Model: 276-1617 | Catalog #: 276-1617) - or a bigger one depending on how much load you intend to drive
2 standard AA batteries.
Some number of bright LED's (I usually use a warm white "straw hat" led from ebay which throws out a bunch of 'candle colored' light in a wide area.

The circuit is pretty simple:








You can use some thin gauge wire (ie 24, 26, 28 AWG) for a few LED's but if you intend to power a whole string of lights (the 2222 transistor should be good for ~800 mA) so that could be ~40 normal LED's which draw 20mA each or up to 5 of my straw hat LED's which draw 150mA each) thicker wire is in order.

The circuit in action:





Also, RE the LED voltage. As long as you stay at or under the LED rated voltage, it shouldn't be too much of a problem, but LED's have no current limiting of their own so going very slightly over the rated voltage will burn them up in short order. Most of the soft white LED's need 3.2-3.5 volts, so they pair nicely with a couple AA batteries or 3 in series on a 9 volt supply. Other colors may not be so lucky, though. Red is usually around 1.6-1.8V so they will burn up pretty quickly with no current limiting resistor.


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## Otaku

I did something very similar using a Darlington, a tea light and a bunch of ultrabrights. The number of LEDs you can put into a circuit like this is really just limited by the power supply. I wired the ultrabrights in parallel to a 4AA pack, rather than in series. I haven't seen any of the "Type 2" tea lights yet. How does the flicker effect compare to those with circuit boards?


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## corey872

Well, yes - limited by the power supply and transistor ratings, of course. If running on batteries, I'd highly suggest matching the bat voltage to the LED requirements to minimize or eliminate the resistor needed and give max light for minimum battery drain. On wall power, it's much less of an issue - wastefull, but we're talking a couple watts of power for 1 month a year.

I bought a couple different brands of tea lights from the dollar store. The ones I like best are "luminessence candles" in a brown "2 pack" package. Though you'd almost have to sample some locally to see what is available and how the flicker looks. I had some others which had an identical looking LED, but seemed to just give random bright/dim pulses.

For the flickering purist, the 'flicker' is not just a bunch of random bright/dim events, but actually a 'train' of relatively steady burning followed by alternating bright/dim bright/dim bright/dim followed again by some period of relatively steady, then another train of bright dim events. I once saw it described as:

Assuming .=dim, o= medium and O=bright, real flickering is like:

OOOOOOoooOOOO....OOOooo...OOOooo...OOOooo...OOOOOO

Some substandard flickers just give:

OOO...OO...OOOOOO..OOO...OOOO... , etc :googly:


Most warm white LED's are right in the 3.2-3.5 volt range so a good match for a 3.0V lithium batt, 2 AA cells in series, etc. I'm hoping to make some red, green, blue and blacklight UV flickers this year, so voltage is going to be all over the charts


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## Otaku

Good description of flicker, Corey. I have an old BLF (Battery Lamp Flicker) board that Hauntmaster used to sell - it has 3 pots that allow you to set those same parameters and with a bit of tweaking you can get a very nice effect. The most it will handle is 12VDC 3A, but that's a lot of LEDs.


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## Jaybo

Otaku said:


> Cool. I assume that this type of LED is different than the standard blinker? Never seen them sold anywhere, but a very useful item.


Here are pictures of the tea light with integrated flicker circuit:


























These work great. I've used the "flicker" LEDs before, but they just basically blinked on and off randomly. These will actually pulse. I would love to find a source for these LEDs!


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## .id.

*Source for just LEDs and lens*

Found these on a parts site I frequent... Not sure if they just blink or if they are a true flicker. Flickering Candle LED with Lens


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## Jaybo

.id. said:


> Found these on a parts site I frequent... Not sure if they just blink or if they are a true flicker. Flickering Candle LED with Lens


That definitely looks like the right LED, but the price is kind of steep. $1.49 for one LED. I can get the tea lights for $1. Now, if we could find someone who sells these LEDs in bulk at a cheap price, that would be ideal.


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## corey872

Yep, that looks like the real deal - nice to know those LED are making it into the surplus market. But I've found tea lights at the local dollar store - $1 for two lights. That gets you the flicker LED, a coin cell battery and sometimes a microswitch for 50 cents ea.


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