Scavenging Poundland LED COBs and a hack

Your average Pound shop or Dollar store usually has some very useful low voltage (about 3V) LED arrays that can be used in projects or to fix other lights.

(Note that some of the round lights may apparently run quite hot.)

The COB (Chip On Board) modules usually have an aluminium backed PCB with flip-chip LEDs on it, protected by a layer of phosphor loaded gel. A flip-chip LED is a bare "dice" with metal contacts formed on the back of it as part of the manufacturing process, so it can be soldered directly in place with no need for bond wires.

For project use these COB arrays will need a resistor top limit current.

In the video I also converted one of the lights into a rugged magnetic emergency light that charges from a USB charger. If making your own in this style the batteries MUST be either Nickel Metal Hydride (NiMh) or old fashioned Nickel Cadmium (NiCad) cells. Non rechargeable cells like alkaline or zinc chloride will pressurise and may explode.
You could also use a protected lithium cell. But it would absolutely have to have protection fitted.

The resistor values can be juggled to suit your needs, noting that continuous trickle charging at high currents will reduce the working life of NiMh cells.

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