These very minimalist G40 (40mm diameter) lamps seem to have a reputation for failing quite regularly. The drive circuitry is the simplest I've ever seen, but has failure built in as usual.
While the E12 festoon seems popular in other countries it is rarely seen here due to our higher voltage potentially causing tracking/flashover issues in the small lamp holders. These ones are punched in parallel onto two core cable, but with clearly visible holes in the base. I've seen this stuff strung vertically and horizontally outdoors here, fully exposed to the rain. It'll be interesting to see how it fares in the weather.
I'd strongly recommend you don't handle these holders while they are wet. Especially with a 220-240V supply.
In the video I did the dooby test and put a capacitor in series with the entire string. The built in resistors mean the lamps share the current evenly if they are identical lamps. To get a good (reduced) intensity you will need a capacitor with a value of at least 1uF for short 230V strings, or more if using 120V strings, or more than one plugged end to end. A safety resistor of around 1 Megohm will need to be put across the capacitor to discharge it when the power is turned off.
Any reduction in intensity will result in much longer lamp life - mainly by reducing the strain on the internal resistor.
With a lower value capacitor these simple lights still work at greatly reduced intensity, and even longer life. The capacitors are standard metalised film type with a rating of 400V (230V AC) or 250V (120V AC).
The AC filaments are odd. I may have to use AvE's copper swing-press to x-ray one.
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16 thoughts on “Exploring 0.5w led festoon lamps and extending their life”
  1. Avataaar/Circle Created with python_avatars fraydnot 2016 says:

    I have seen solar yard decorations using one of those bulbs powered by three AA's.

  2. Avataaar/Circle Created with python_avatars Martin Clemesha says:

    I have a set of these powered by a rechargeable solar panel. Been running a couple of months and all seems okay so far, and seem to cope with all this rain we've seen lately. The lamps and the holders seem to be quite well made, despite not being fully waterproof. My G40 bulbs look like they are blown from plastic rather than glass.

  3. Avataaar/Circle Created with python_avatars ‍1marcelfilms says:

    I took a 50w floodlight (real 30w) and made it 10w

    Very great results.

    I might do this with a 100w floodlight and make it 20w

  4. Avataaar/Circle Created with python_avatars ブブ says:

    Theoretically wouldn't putting two leds in parrell pointing opposite directions be safe, since there is a resistor in series? I would think the LED forward biased would drain off enough of the voltage that the reverse biasing wouldn't be high enough to do damage. Basically it seems like it is just the relatively high value series resistor is what makes these LEDs safe to run on AC.

  5. Avataaar/Circle Created with python_avatars James Melrose says:

    I have this exact set! Keen to extend the life, is the 1U 400V capacitor definitely to go in series with the set and not parallel across L and N? And should the 1M resistor be across the capacitor legs (so also in series) or across L and N?

    Also, would a 2W metal film resistor of 1M be enough power to discharge the cap safely?

  6. Avataaar/Circle Created with python_avatars tim1724 says:

    E12 is also known as "candelabra base" here in the US and is mostly used for chandeliers and similar indoor lighting where lots of small lamps are used in one fixture. The classic C7 indoor Christmas lights used the same base. Outdoor (C9) Christmas lights used the much larger E17 ("intermediate") base. What you have there looks just like a typical 1960s-1980s indoor light strand. (In the ’90s they made them slightly more rugged and added a fuse.) The build quality on outdoor light strands wasn't much better. Just bigger E17 sockets to hold the C9 lamps. I believe Europe typically uses E14 where we use E12, just as you use E27 for normal lamps where we use E26.

  7. Avataaar/Circle Created with python_avatars Jerry Ericsson says:

    Many years ago, when I was a young boy growing up on an old farm that had no power or running water, one Christmas our folks took us into the small village of Thunder Hawk SD. There was a house beside the road as you drove into the village that had blue Christmas lights all around the house across the barn and out buildings. I was transfixed! That blue glow was the most amazing sight I had seen in my young life time. That sight has stayed with me now all these 70 years or so, and over the years I have attempted to reproduce that seen with little luck. The closest I have come to date were some bright blue LED's with shields the same size as those old large Christmas lights along with blue LED net lights over our evergreen hedge that lines the front of our little ranch house some 9 miles from that very house in Thunder Hawk. While the street lights of our town cut them down considerably and you need a LOT of snow to get the right reflection factor it is close enough to give me a bit of the thrill equal to that day back in the 1950's when I first saw those lights. I am sure the old Christmas Lights were the same size as the ones you are playing with, the ones I tried to replace them with are not screw in at all but pop off covers over push in flat faced LED's. I have had to replace many of those LED's over the years and now I am no longer able to put them up or take them down, they stay up year around but don't seem to have suffered much for that sentence, I have had less trouble with them staying up year around then the putting up in the fall and taking down in the Spring.

  8. Avataaar/Circle Created with python_avatars Groot says:

    Mmm a big resistor, wonders for power efficiency 🙄

  9. Avataaar/Circle Created with python_avatars RiderBlitz says:

    These lights are so cuteđŸ’–đŸ„°đŸ˜

  10. Avataaar/Circle Created with python_avatars James W says:

    Hi Clive, I just watched your vid on tasting methylated spirits….. Have you tried running it through the water distiller?

  11. Avataaar/Circle Created with python_avatars Stephen WONG says:

    I'm deeply concerned about your safety! I'm not comfortable to see such bare metal, twisted wire, kind of practice, especially as you said, you're in UK, and playing with 240V AC (rms, or 678V ptp)!

  12. Avataaar/Circle Created with python_avatars MrBlawson7 says:

    What is that connector called, in which you placed the jumper and the 1uF capacitor?

  13. Avataaar/Circle Created with python_avatars TheWarped45 says:

    I thought led diodes rectified voltage without the use of a diode or full wave rectifier.

  14. Avataaar/Circle Created with python_avatars smitajky says:

    You comment over possible problems with the volts and the rain. Now I have experience with my 6000 volt electric fence unit. In the rain. clean rain does not cause an arc over even 5mm of clearance Equivalent to just 1/4 of a mm at 300 V AC. DIRTY water ( ants, slugs, dust, dirt, salts etc) give very different results. 240 V can arc across several cm if ants choose to build a nest. Which means that keeping the lights clean is far more important than the size of the base or even keeping them dry. Dirt is always your enemy.

  15. Avataaar/Circle Created with python_avatars Andre Beekaert says:

    The E14 foot is well known in Belgium. Mostly used indoor for night lights. For outdoor lighting in a string, we usually use E27 base with max 15 Watt filament lamps. Now of course everyone has switched to LED string in tube form and waterproof.

  16. Avataaar/Circle Created with python_avatars RĂœĂĄn TĂșçk says:

    What we would call “festoon” is AKA ‘tube lamp’, connector pins at each end not candelabra-screw base.

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