Category: Electrical

I have recently purchased or attempted purchase of several nominally 18W LED circular plates and associated 230VAC drivers.

The circular LED plates all had 36 x 5730 nominally half watt white LEDs arranged as 18 parallel pairs in series.

It is difficult to find datasheets from reputable manufacturers of 5730 LED. Cree makes 5630 which are similar size (though different footprint) and also rated at nominally 0.5W.

Above is the V/I characteristic from Cree’s J series datasheet with an approximation of the 0.5W line superimposed in red. The V/I combination for 0.5W is at the intersection of the two lines, about 162mA and 3.08V. Continue reading Chinese LED ratings – LED plate drivers

This article describes the internals and basic test of a no-name Chinese 4′ T8 LED replacement.

The lamp is a Type B DEP (double ended power) configuration, cool white, it requires rewiring of a traditional magnetic ballast fitting or e-ballast fitting. Don’t attempt this unless you have the needed competencies.

It has no rating label, no information about its configuration on the lamp, no warnings about compatibility… so very Chinese.

The lamp is rated at 18W 1750lm, claimed life is 50,000h but you should take that with a grain of salt. The lamps cost $6.40 ea in a pack of 10, including delivery. They were well packed and the pins had a small plastic protector.

Above, the powered end of the LED strip and the LED driver partially withdrawn from the hollow aluminium extrusion. Continue reading Chinese T8 LED 4′ tube teardown

Some months ago I purchased  a TKDMR TD2B LED tester.

Above is the tester. It comes with a 3 month warranty, FWIW. Continue reading TKDMR TD2B LED tester review

I recently purchased two packs of 2x Osram Substitube LED replacements for a T8 36W florescent tube. The price per tube was about double that of a T8 fluorescent, and claimed life was 30,000 hours.

Note that LED life is usually an estimate of the time for 50% failure. Curiously, Osram individual LEDs have lower lifetime estimates for single LEDs, strings of LEDs will have lower lifetime, and lifetime for say 5% failures would be even lower. On the basis of experience with LED lighting, it might be optimistic to think that most of these lamps will last at least 5,000h.

In the event, three of four tubes had broken glass (yes, they use a glass tube much like the T8 fluorescent tube… though not sealed at the ends), and the other was DOA, no light output.

The LED driver is attached to pins at one end of the lamp, and covered by a label over the glass. Note that there are several incompatible schemes used in T8 fluorescent replacement LEDs, the other scheme bonds the adjacent pins at each end of the lamp and connects line and neutral to opposite ends. Osram calls this a “Type A” connection, and as the name suggests if can be fitted to an ordinary magnetic ballast luminaire PROVIDED the original starter is replaced with Osram’s “LED starter” which is actually a HRC fuse of around 1A rating.

Above is the top view of the electronics. Continue reading Osram Substitube tear down

I purchased a kit to convert a oyster luminaire to single colour LED on eBay. The kit was nominally 18W, supplied with the 5730 LED plate and driver module for about $10 incl shipping.

A cautionary note: do not play with these things unless you have the necessary competencies.

The thing was packed in nothing more than a plastic mailing bag and was bent in several places in transit from China. It was not usable in that state and some LEDs were not working so my money was refunded in full (after the usual tug-o-war eventually resolved with eBay intervention). It had to be straightened to be usable, but at the risk of damaging LEDs and possibly cracking or compromising the insulation layer.

Above, after flattening the back plate, nearly half the LEDs are not working. Continue reading Conversion of oyster luminaire to LED