Wire & connectorsBench electronicsTest and identify

Inductive charge coil

Also called Qi coil, toothbrush coil, wireless charge coil.

A flat coil used to couple power across a small gap. Toothbrush docks and Qi pads. The coil without its tuning capacitors and driver is just an inductor. Keep the pair of coils if you want the link to keep working.

If you are new to this category

Wire and plugs are how power and signals move. The insulation is the safety, not the copper. Ethernet cable is fine for small signals and low voltage. It is not a substitute for a power cord. A connector you can unplug is worth more than a wire you have to solder every time.

Match the plug that came with the brick. Center-positive is common and not universal. The drawing on the label is a map: the dot is the center, the ring is the outside.

Center pin and outside sleeve

The drawing on the brick is the polarity. A dot inside a C-shaped ring means the center is positive when the plus sign points at the dot. Measure anyway. The two common hole sizes, 2.1 mm and 2.5 mm, almost fit each other and that is how the center pin gets bent.

Lithium-ion cells. A punctured, crushed, overcharged, or reverse-charged cell vents and burns hot enough to ignite the bench. Swollen pouches are already failed.

Specification. The right-hand column is what is typical. The label on the part in your hand wins if they disagree.
What to look for	Usual figure
Gap	Millimetres, not centimetres. These are not transformers you can put across a room.
Qi	A specific frequency and a handshake. A bare coil will not charge a phone just because you fed it 5 V.

Volts are electrical pressure, amps are how much current is flowing, and ohms are how hard the part resists that flow. A higher voltage than the part was built for is how salvage parts die on the bench. If a cell in the table says “read the stamp”, that stamp is the whole specification.

What people actually use it for

The original dock
A short-range power experiment with both halves and the original circuit

Leave this one when

You have one coil and a plan for a 50 W charger. That is a design project, not a salvage.

Buying a new one is the better idea when

A Qi module. The protocol is the product, not the copper.

How to tell if this one still works

Inductance if you can, or the original pair at the original distance.

Tools you will want: Meter.

Where people actually find it

2 notes, most useful first. “Leave it” means the part is in that machine and you should not take it: it is dangerous, worn out, or only useful if you already know that exact repair.

Harvest at a glance
From	Call	How many	How often	Where it sits
Electric toothbrush	Worth it	2	usually	Handle and base.
Mobile phone	Bonus	1	sometimes	On the back, inside.

Worth pullingElectric toothbrush2 · usually
In this particular machine
A pair. The gap has to stay small.
Where to look
Handle and base.
How to get it out
Keep both.
The condition to expect
Good.
Bonus, if you are already in thereMobile phone1 · sometimes
In this particular machine
A Qi coil. The phone still needs the handshake to charge; the coil alone is an inductor.
Where to look
On the back, inside.
How to get it out
Peel gently.
The condition to expect
Fine.