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A look inside a 40W LED lamp with 660 LEDs.

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A very interesting lamp that uses a HUGE array of standard surface mount LEDs wired as 66 parallel strings of ten series LEDs. The use of multiple parallel circuits of ten LEDs seems to be a very common driving technique, as used in most of the 20-100W LED floodlights.
The driver is surprisingly chunky in this lamp, and has a lot of interference suppression circuitry on both the incoming mains and the outgoing DC to the LEDs.
Demo of lamp at
The main control chip is an SN03A driver chip dedicated to the function of driving LED lighting loads with very good power factor. It doesn’t seem to use significant smoothing on the incoming rectified mains, but rides the waveform, switching the transformer with a single MOSFET. The transformer has a second winding on the primary side to power the chip itself after it has started running. Current in the primary is monitored on each switching cycle via a sense resistor in series with the MOSFET.
There is opto-isolated feedback from the secondary side with efficient low-loss current detection being implemented using an LM258 op-amp. The secondary rectification and smoothing is based around a TO220 style diode package on a heatsink and two paralleled smoothing capacitors.
There is an auxiliary secondary winding on the transformer for a cooling fan (not fitted on this model), which uses a single rectification diode and a 22uF capacitor to create a simple unregulated DC supply.
The LEDs are probably run at a current of 1200mA split across 66 parallel circuits, giving a typical LED current of around 18mA.



Inside a 4.5W LED 300mm / 1-foot T5 link light style fitting.

Not the first of these I’ve opened, but I actually like this one better. It uses the same style of loop through connector that the other fitting I took apart used, but in this instance it uses a very standard GU10 style LED driver to run a series parallel array of LEDs at 15V and 300mA. I like that little feature. The fact it uses a standard power supply that you can buy on ebay for a dollar. The LEDs are on an aluminium core PCB, or to be more accurate a strip of aluminium with a layer of fibreglass PCB material laminated on one side.
The connection system is fairly standard for these, with a “clover” style connector using copper coated aluminium wiure in the short flex provided, and a friction earthing system onto the aluminium housing.
Two naughty bits… One of the crimps inside hadn’t been crimped and popped off the twisted wires, and there was no end-cap for the end of the fitting meaning the link-through pins weren’t covered.
It’s actually quite a nice little light. This one may actually find its way into my kitchen.



New, and VERY interesting Poundland 5W LED lamps.

Note that in real use the 5W lamps are showing signs of heat related failure. So it may be better sticking to the more sensibly rated 3W units.
Poundland is currently engaging in rapid evolution of its range of LED lamps with a really surprising range of 3W, 5W and 6W LED lamps. I started looking at them with a view to covering them all in one video, but had to restart with just the most recent when they turned out to be somewhat more interesting than I had expected.
The most notable features are the use of multi-chip LEDs to fit a lot of LED chips in series in a smaller number of packages, plus the use of X2 suppression capacitors in the capacitive dropper circuit.



Teardown of a flat LED panel ceiling light.

These seem to be everywhere on ebay, so I randomly made a bid on one from a UK supplier and won it. So here’s a full teardown, showing what’s inside both the light and power supply.
I also experiment with some alternative light sources including an RGB one.



Extra long LED filament lamp teardown.

Another new twist with LED filaments. This style is designed to emulate traditional retro filament lamps with a very long LED filament that emits a very golden light.
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Making a DIY tubular glass LED filament lamp.

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I had some LED filaments left over from my big open filament lamp project, so I spontaneously decided to make a tubular LED filament lamp after discovering that test-tubes fit nicely into salvaged lamp bases.
Initially I was tempted to cheat with the absolute minimum number of components by using a single diode instead of a bridge rectifier, using a single current limiting resistor and omitting the capacitors discharge resistor, but then I decided to do it with a full circuit. This was a good approach because the circuitry is visible inside the glass tube and looks good.