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I have a set of battery powered candle lamps on a dining table, in a display cage.

I converted the candles to run through a DC transfers and battery eliminator (due to the amount of AAA batteries we were getting through - rechargeables only seemed to last a couple of days)

Unfortunately the cats play with the cable and keep dragging the lamp off now.

So I had a thought of transferring the power wirelessly through the table to the base of the candle stand and so on from there.

Is it possible to shift about 200mA through a 1" table and make a wireless power transfer coupler?

Thanks.

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  • \$\begingroup\$ Sorry, typo - Using a DC Transformer (230V ac to 4.5V dc) - not DC transfers! \$\endgroup\$
    – Petey
    Commented Oct 15, 2017 at 9:10
  • \$\begingroup\$ Why not use LiFePO4 batteries instead? \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Commented Oct 15, 2017 at 9:11
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    \$\begingroup\$ @Petey: Edit your post and delete the comment. \$\endgroup\$
    – Transistor
    Commented Oct 15, 2017 at 9:11
  • \$\begingroup\$ 'shift 200mA'? Power is what gets shifted, not current. However, if we assume from 'a few AAA's' that we're talking about 5(ish) volts, then 200mA is 1W, which seems perfectly reasonable. Wireless power transfer needs a distance of less than the coil diameters to be reasonably efficient, so it looks practical, for reasonable candle stand base diameters. What's the table thickness, and the stand diameter? \$\endgroup\$
    – Neil_UK
    Commented Oct 15, 2017 at 9:13
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    \$\begingroup\$ Why don't you use some insulated staples (or other similar device) and simply fasten the cord to the table? \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Oct 15, 2017 at 9:32

1 Answer 1

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It's possible when the candelabra isn't made of metal – and that requirement would kill all the romance, wouldn't it? But then, battery powered candles already do, I think. Makes me think I was eating at Legoland Burger King.

You had to install an ironless magnetic coil below the table, and connect it to a power amplifier feed with a frequency of roughly 15kHz. Install another ironless coil into the candelabra bottom, connect its terminals to antiparallel LEDs. You are done.

Why 15kHz? Because the amount of copper needed for the receiving coil drops significantly with frequency, so you can have a smaller coil. And because 15kHz is something an audio amplifier can deliver. You could even make a CD with the required signal.

Why ironless? Because iron wouldn't help you anything at 15kHz.

And why can't your candelabra be made of metal? Because the 15kHz transformer would induce eddy currents in it, making it heat up like a pot on an inductive stove. Well, not so much, but it draws power which can't be used for the LEDs.

(A better setup would indeed feature a magnetic core, but made of ferrite and at least 2" in diameter. Very costly and you need the same in the receiver.)

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