120V A/C Lamp Flicker from LED Votive Candle Type 1 (COB)

Need some flickering lights to make your Halloween Haunt complete? Frustrated by other solutions? Like to melt solder and re-purpose electronics? Then this Instructable is right up your alley.

This Instructable addresses only the actual flicker electronics. Integration into lanterns, pumpkins, candles, etc. is an exercise left to the reader. Personally, I'm using this circuit in two lanterns, a molded plastic pumpkin and for a string of pumpkin lights.

Note: There are at least two types of LED votives. This instructable will deal only with what I call type 1 devices - so-called because these were the first type I found. Type 1 LED votives have a small circuit board in them with a chip-on-board (COB) circuit and an LED. Type 2 LED votives have the circuit embedded in the LED itself, similar to a standard flashing LED. I have not yet determined a usable configuration for this type. For this instructable, you will need the type 1 COB LED votives. Unfortunately I think the only way you can determine what you have is to open them up.

Disclaimer: This circuit uses 120V A/C house current. It is quite capable of killing you if you are careless. All devices using this circuit should be housed in an insulated container (e.g. plastic). This is not recommended as a beginning electronics project. The poster disavows any responsibility for damages, injuries or death sustained as a result of constructing or using this circuit.

Hey, we all know anything really fun can kill you ;-)

Another note: This instructable is somewhat of a skeleton (hey, it IS Halloween). The author expects anyone knowledgeable enough to construct this can figure out how to put it together on something other than a breadboard.

This circuit is NOT approved by Underwriters Laboratories!

Step 1 Parts List

Of course you'll need some parts:

- 1 LED votive candle
- 1 extension cord (to provide power to circuit)
- 1 lamp and socket that you want to "flicker"
- 1 full wave bridge rectifier -or-
- 4 200v or better rectifier diodes to construct bridge rectifier
- 1 470nF 250v capacitor or similar/better
- 1 3.1v zener diode
- 1 470uF 10v electrolytic capacitor or similar/better
- 1 220 ohm resistor
- 1 MOC3023 opto-isolator/triac driver
- 1 BT134 (or simiar) triac

I salvaged the 470nF 250v capacitors and full wave bridge rectifier from a CRT monitor.

I used the extension cord to provide a power cord for the circuit, cutting off the triple tap end. I've also used the triple tap connected as the "load" for the circuit so I can plug in a string of novelty lights.

Note: If you try to drive a large load with this circuit, the triac will heat up significantly and require a heat sink.

You'll also need perfboard, soldering iron, wire, strippers, etc.

Comments

[highvoltageguy]

This is cool but one thing i would not recommend is 120vac on a breadboard

[matrice666]

YOU SEEM TO BE GOOD WITH ELECTRONIC AND NOT ME ! lol so ... lets say i would like to make it run on batteries would it be possible ... lets say D batterie

[corey872]

On a side note, I've had good luck with the 'Type 2' - "LED only" flickering candle just tying the LED to the base of a suitable transistor (2N3094, 2N2222, etc)  Then using the transistor to drive 1-3 150mA warm white 'straw hat' LEDs.  The flicker LED and straw hat's are all happy @ 3V from a pair of AA batteries, and the 2N2222 is happy up to several hundred mA which could be ~5 straw hats in parallel.

I suppose you could add as many LED's (or incandescent) as the transistor ratings will support.  I've found a single 150mA LED closely approximates the brightness of a candle, 2-3 really put on a bright show.

Nothing like a couple dozen flickering pumpkins lighting up the haunt on Halloween.  I've even gone so far as to try red, green, blue and blacklight flickering pumpkins - though I guess I'm a purist at heart and like the warm yellow glow the best.

[sr1sws]

Excellent!  Happy Halloween!

[FirefighterBlu3]

does the schematic need correcting for the location of the 470nF cap?

[sr1sws]

No, don't believe so. The 470nf capacitor is used to limit the AC current. Google "transfomerless AC DC circuits" and see if you agree.

[FirefighterBlu3]

i agree it is needed, but i think it's located incorrectly and your breadboard agrees. in your schematic it is upstream of both the bridge and the triac/lamp, but on your breadboard it limits only the bridge - which i agree with.

[sr1sws]

Yupper, I see what you're saying and agree. Hmmm... wonder if anyone's tried this according to the schematic and ended up cursing my name? Good catch, my bad!

[FirefighterBlu3]

not a prob, i make plenty of revisions on my own stuff ;)

[corey872]

That is too funny. I will have to 'watch' for my pumpkins playing songs now!

[Scubabubba]

Nice! An old trick from Halloween haunters is to splice a CdS photoresistor from an automatic nightlight into the input of a household dimmer switch, then drive the photoresistor with a standard flicker bulb. Your signal side looks like a big improvement on the flicker lamp/CdS cell, which was a bit delicate to adjust. You might be able to replace the load side of your circuit with the dimmer switch and simplify the build a bit. It has a built-in heat sink so you can drive up to 600 watts and there's some adjustability via the knob. If I get the chance to try it this year I'll see if I can make a hybrid.

[sr1sws]

Thanks! I'd used the neon flicker bulb/CdS photoresistor/dimmer before and like you said, they are VERY picky. Also the neon flicker bulbs age and eventually stop or become "unflickery".

I mucked around some with what I call the Type 2 LED votives which have the flicker circuit built into the LED and had some success. Put the 'flicker LED' in series with the input of the opto-isolator (observe polarity). You'll also need to use a 5.1v zener diode as the LEDs in series will need higher voltage. You may also need a larger current limiting capacitor off of the A/C to supply enough current to keep the voltage up. I was successful with a 470nF capacitor.

On the triac trigger side, you can try using a small neon lamp instead of the resistor feeding pin 6. This *seems* to produce a more 'flickery' output on the A/C bulb. A higher value resistor may produce the same result but I haven't messed with that yet (and would be cheaper than the neon glow lamp). I snagged that idea from a strobe trigger circuit that used an opto-isolator and triac.

I'd also thought about hooking up the flicker circuit in series with a dimmer - using one of my "flicker circuits in an extension cord" setup along with one of my "dimmer in an extension cord" setups - but hadn't actually tried it. Should work OK, I think. May have some surprises as the MOC3023 I used is a "random phase triac driver" which means it will fire the triac wherever the voltage is in the 60hz A/C sine wave. I suspect (but don't know) that dimmers are "zero crossing" circuits, which means they turn on/off as the voltage sine wave passes zero volts. May not matter at all since the voltage goes to 0 60 times a second (or is 120 times a second?... whatever).

Good luck and enjoy!
Steve

[Scubabubba]

I haven't got the votive yet so I don't know which way I'll go. You can get neon lamps from those tiny puck-shaped night lights, 2 for <$1. Do the type 2's play music too? James

[sr1sws]

Good thought on the night lights for the neon bulbs. The ones I have were salvaged from old equipment - I *assume* they are NE-2 type - they look like it.

I've decided the neon lamp does provide a much better result flicker-wise. They work with either the Type 1 or Type 2 votives, so I'd suggest that instead of the resistor. I put a potentiometer in place of the resistor on the output side, but didn't like any of the results. The neon glow lamp works much better. I may retrofit my circuits once I have enough glow lamps.

As far as the Type 2s playing music, I just tested that. It's not music, sounds more like Morse code (I doubt that it is). I listened for a bit - the volume is really low - to see if I could detect a pattern, which I did not. Seems pretty random.

Here's my free product development tip for the day to any company that reads this stuff. There are a number of companies that produce ceramic or porcelain "village" buildings basically in O gauge scale. Department 56 produces very nice high end stuff (yes, I collect). Most of these have an era where lanterns or gas lamps were used to light the streets, and they offer LED versions of the lamps to go with the villages. I'd previously used a different flicker circuit to add interest to these, but of course the whole string of "gas lamps" flicker in unison - only slightly more interesting than static light. So, these companies should source the flickering LEDs in the appropriate size and use them in their lanterns/gas lamps so each lamp flickers independently. I think that would be really awesome.

Now if somebody does that and makes money, I hope they'll do the right thing, chase me down (I'm not hard to find) and compensate me for my brilliant idea ;-)'

Steve