DGT coils are cylinders, two sizes:
Where did you buy these?
12 mm x 12 mm x 27 mm (for kings, queens & rooks)
12 mm x 12 mm x 14 mm (bishops, knights & pawns)
Well, actually, these are the hole size recomendations, the coils themselves are just a hair smaller.
-Izmet Fekali
Only logical technique to weigh pieces With DGT coils: use naturally dense and heavy materials to make the pieces out of and that won’t affect the coils in any way.
The beauty of the Certabo is that they can be used with virtually any chess set that has a flat base.
It’s just a matter of time before the Certabo protocol will be used in conjunction with all the favorite applications that players use worldwide including Chessbase, Fritz, Arena and Aquarium.
Gave this a go. Used double sided sticky tape and aluminum foil (easy to undo without damaging the felt bottoms of the pieces). I wanted to see how it feels with these first version HOS Reykjavik 72 pieces, before I make it more permanent with the stickers and tiles others have used. The king and queen in this set have a wide base, but still fit within the “circle”. Can’t justify buying yet another set and may as well get some use from these pieces. Much nicer to play with and looks better, even if very slightly on the larger side. The one thing I am a bit concerned about is the weight of the pieces. This is a heavy set, has anyone any concerns with the board not being able to handle that or the pieces causing damage over time? What do you guys think?
Would placing foil on the bottom of a DGT-enabled piece allow it to work on both DGT and Certabo boards, or would it interfere with play on either or both boards?
It would work for the Centaur but not for the Certabo. You’ll need to buy the proprietary chips for the Certabo.
Those pieces look outstanding! Thanks everyone for the information. I have just ordered a Centaur so trying to get an old wooden set ready for when it arrives!
Does anyone have a UK link for the 25mm aluminium foil circles? I'm assuming they cannot be magnetic (lots of them available).
Found this on YouTube:
Hi everyone. I've recently bought a DGT Centaur and have modified some wooden pieces that I bought from Chess Bazaar to work with the board. The Chess Bazaar pieces use a vinyl faux-leather base, which actually works well in this setting (compared to felt) - stickers just adhere better.
I can confirm that the 3M aluminum foil tape 0.75 inch diameter circles work very well: https://www.amazon.com/dp/B007Y7DKEK?psc=1&ref=ppx_pop_dt_b_product_details From Amazon, they are quite inexpensive.
However, the disadvantage in doing so is that the smooth surface of the aluminium means that the pieces slide/slip on the board easily. It's no worse than the original plastic pieces which come with the DGT Centaur, but still kind of annoying. It's something that you notice immediately.
I've discovered another product which works extremely well. The 3M conductive fabric tape does the same job as the aluminium tape in setting off the inductive sensors, but have a slightly grippy surface: https://www.amazon.com/dp/B00M9WEXBO?psc=1&ref=ppx_pop_dt_b_product_details
There is a 3M product where this tape is in circular shape stickers, but I couldn't assess it in Australia (Amazon US wouldn't ship it for some reason). For these 1 inch x 2 inch rectangles, after I adhered it to the base of the pieces, I used a sharp hobby knife to trim the edges.
A company called Demon Tweaks supply aluminium stick on discs which work perfectly with the Centaur, I have been using them for over a year now.
https://www.demon-tweeks.com/uk/demon-tweeks-aluminium-self-adhesive-foil-discs-609511/
This set from Chess Empire - https://www.etsy.com/listing/705668971/contemporary-series-brass-chess-pieces?ref=yr_purchases - looks and works great with the modern gray and black plastic Centaur. It is very heavy brass and a little scuffing of the bases has the added benefit of stability.
I've discovered something interesting to share.
I hacked two wooden sets I have, both weighted, one with the silver foil dot method, the other silver tape, and both work fine.
ButI have a standard, run of the mill plastic weighted set, and I cannot get Centaur to play nicely with these pieces. I've tried them without foil, thinking maybe the weights themselves might be enough--but nothing. I've put a foil dot on the bottoms with mixed results. I've covered the entire bottom and it's the same mixed results: eventually Centaur calms down and stops blinking, but after a few moves it does not recognize the pieces and does its circle dance again.
Upshot: works fine hacked with wooden pieces--but I can't get it to work with my plastic piece hacks.
Anybody else have the same issue? Any ideas why?
Take the weight out of the plastic pieces and use the foil method again. You’ll be able to isolate the issue that way.
The issue must be the weights. I was unable to pry one out, but instead hacked a Halsam plastic set from around mid century I think. Those are hollow, unweighted, and it worked beautifully. Since I'm a fan of plastic sets from the 60s-70s (they're fun as long as you're not playing speed chess and toppling them over!) --I may try to get a hold of a plastic Russian unweighted set with a king at least 3" to hack that for some fun variety of aesthetics. Anything smaller than 3" is just too small for the board.
So, in short--it's not that DGT Centaur hates plastic, it's the kind of weights used. My wooden sets that I've successfully hacked are weighted, but I've put the foil dot right over the felt and it may be the thickness of the felt that cancels the weight, or it's a different weighting mechanism. As a matter of info, I bought some standard plastic 3-3/4 chessman in red and silver and had the same problem. It could be plastic pieces use different weights. Whatever the reason, this plastic set, originally hollow, works well, looks great and is fun to play with. (Halsam set #421, King = 3-1/8"). So, here's an alternative to a wooden set hack! I continue to love this board and am hoping we can also hack pieces on the upcoming Pegasus board! 
I have also discovered that the FIDES style plastic pieces from the World Chess starter set also seem to work well out of the box with little mod. The pawns are sometimes a mystery to the Centaur but the foil dot application solves that, and I’ve used the larger pieces right out of the box without modifying them at all.
DGT coils are cylinders, two sizes:
12 mm x 12 mm x 27 mm (for kings, queens & rooks)
12 mm x 12 mm x 14 mm (bishops, knights & pawns)
Well, actually, these are the hole size recomendations, the coils themselves are just a hair smaller.
-Izmet Fekali
Wow, a lot bigger than I though they would be. No wonder DGT pieces are hard to add weight to.
The Certabo Chess rfid tags/chips seems to be the more elegant solution. But it looks like they are putting themselves in a slightly different niche rather than trying to go head to head with DGT.