DIY: Adapting Out of Tricky Light-Bulb Situations

Being the resident electronically minded person in the house, I normally take charge of all the lighting in the house as well. Unfortunately, in the house we’re living in at the moment, some really oddball builder has decided to use visually identical fixtures, but with some Bayonet Cap (BC, B22) fixtures mixed in with Edison Screw (ES, E27) fixtures.

It seems that Australian hardware stores normally stock BC fixtures almost exclusively, but, as a bit of a habitual IKEA-visitor, I end up picking up some “European” design fixtures as well. This means more ES fittings, as well as a mixture of Small-Edison Screw (SES, E14) fittings. Keeping adequate spare globe inventory in all the formats was getting quite tricky – especially as some of my more favourite LED globes come in different versions for each base.

As a kid, I’ve always wondered why didn’t people just have adapters for both globe formats. I had reasoned that they may be difficult to get approvals for safety in Australia, and the high heat of older incandescent globes could make them failure prone. But since we’re all for LEDs and CFLs nowadays, this issue is somewhat less of an issue now.

Despite this, you don’t see them being sold in shops normally. A little cursory search on eBay when I was doing some other shopping seems to show that they do exist, which is good news for me.

BC (B22) female to ES (E27) male Adapter

All of these items were generic unbranded eBay items from some Chinese accessories supplier, mostly costing about AU$1 inclusive of postage. This adapter allows you to use your BC globes with ES fittings.

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The adapter itself uses a plastic body, with cut-outs for the bayonet cap pins which seem to have a peculiar taper and angle. This serves it to make it slightly less likely for a globe to slip out even if it was half un-twisted. The internals seem solidly built with two springy brass pin contacts, and the ES cap seems to have a decent solid plastic insulator and metallic contact.

Of course, as a low cost item, it comes with no safety approval printing, or even ratings. However, it’s safe to say that these are only intended for LED and CFL usage, and can only carry 2A maximum. As a passive wiring adapter, there really isn’t that much that can go wrong with it bar a failure of contacts or insulation.

Because it has a relatively low profile, it doesn’t add that much length to the globe, which is good news for avoiding potential interference issues with fittings due to the increased length.

ES (E27) female to BC (B22) male Adapter

Some searching on eBay also allowed me to find a unit that goes the other way. This is good if you want the widest possibilities in mixing and matching globes that you have left to their best use fittings.

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This adapter is physically longer than the one above, owing to the need to accomodate the full ES base itself. An outer aluminium can forms the threads and one contact, which makes for a good thick contact, and a copper-coloured folded centre contact provides the other contact. This folded contact isn’t backed by a spring, and thus might be subject to fatigue over time, which could limit the reliability of the adapter over time.

The BC base seems to be a traditional base as you would see on older CFLs and glass bulbs, featuring a full metal construction outer (making it more durable) and solder-bubble style contacts, which are compliant and make good contact with the socket.

As above, there are no markings of limits and safety regulatory compliance.


With these adapters, it was possible to make use of the IKEA G94 shaped LED bulb that had a throat too wide to fit in any of my fittings, and also insert my “right angle” dangle cable as well, while keeping the ES fitting at the end via a double-adaption. Frankenstein!

It clicks … at IKEA

In my earlier review article, I noted that IKEA had stopped selling any BC globes, which they did in the past. I suppose that’s not unexpected since none of their products actually use the BC fitting, but then again, what about the regular householders?


As it turns out, they have you covered with the Koppla, a packet of two E27 to B22 adapters, which are sold at retail for AU$2.99. It comes with a leaflet that reminds you not to dispose of such electronic waste in the bin, but is otherwise just two adapters in a bag. It’s slightly more expensive than the eBay products, but they use a different design.


One advantage of the Koppla is that it is shorter, thus less likely to cause fitment issues in luminaires.

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The adapter itself is made on a plastic body, featuring some metal pins to ensure durability in mounting. The contacts on the BC side are brass contacts, of small area to just match the mating socket. The internal ES contacts are just simple strips of copper-like metal, one “touching” against the side, and the other touching against the middle, with the ES thread formed by the plastic body of the adapter. This seems to be a less reliable and durable configuration, but it is also much simpler and likely to be sufficient for all purposes.

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But the biggest advantage? It’s got some regulatory approvals, so it’s a better bet when it comes to safety. It claims to have CE mark, Intertek S mark and NSW Fair Trading approval number of NSW26793 for Australia. It has well defined limits of 3A, 250V and 40W. This particular adapter was Made in China in Week 52 of 2014.


I think it’s highly likely that many people aren’t aware that you can actually buy such adapters to make your life easier. While it won’t ensure the adapted light globes still fit in the fittings, it can make inventory management easier, and it can make sure that even in an emergency, you’re not left in the dark. It also opens up quite a lot of adaption possibilities, although one should exercise some caution when it comes to electrical safety, especially with direct import products. There are many other adapters available, including splitters, goose necks, etc. It reminds me of the whole idea that good ideas are likely to have been “already done” – indeed, they have!


About lui_gough

I'm a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!
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One Response to DIY: Adapting Out of Tricky Light-Bulb Situations

  1. blouis79 says:

    Perhaps you could comment on the the origin of BC and ES. The Edison Screw fitting grew up presumably in USA with 110V. The Bayonet Cap presumably has origins in UK in 240V environment. Small bayonet fittings dominate in cars where vibration is an issue. How did ES become acceptable for 220-240V environment? I’m guessing that ES sockets are cheaper to make than BC sockets with the simple pressed/bent contact vs sprung loaded solid contact for BC.

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