Refurbishing a Small Fluorescent Fitting - 15/05/16
Recently, many corporate environments have been replacing their fluorescent lights with LED refits. These refits sometimes take the form of retrofit LED-filled "fluorescent tubes". However, these refits are often dim owing to the fact that the LEDs are all packed closely together and therefore heat build-up is problematic if high power LEDs are used. As such, only relatively low-power (dim) LED chips could be used.
Because of the aforementioned limiting factors, in recent times, companies have been replacing entire fluorescent light fittings with integrated LED types. Therefore, in more recent times, one can find many fluorescent fittings, complete with the tubes, set out for disposal. Such was the case with the one which I recently found.
When I found the fitting it did not have a cable or front cover. It is slightly less than a metre long and 20cm wide. Inside, are two short T8 fluorescent tubes and dual starters, one per tube. Unfortunately, the fitting had been out in the rain so it spend a couple of hours drying out in front of my home-made box fan. Next, it needed cleaning. Both the tubes and the fittings were wiped with a non-abrasive towel.
Below: the dual starters in the fitting:
Once the fitting had been cleaned and dried, it was time to do some testing. I removed the two starters and tested them using the starter tester which I made in this article: Alternative Uses for a Fluorescent Starter. One starter was working but another one was shorted and had to be replaced.
I next had to attach a power cable to the fitting. The fitting (somewhat unusually for a light fitting) needed to be earthed because this helps the fluorescent tubes start, particularly when cold. I eventually settled on a power cord with a 3-pin female IEC connector into which a standard, computer-like mains cable could be connected. Once this had been done I was able to test the fitting for electrical safety (earth continuity etc.) before connecting it to the mains.
Below you can see a picture of the fitting when running in a dark room:
A final but important alteration was the addition of a front cover since, as you can see in the picture above, the fitting had nothing over the live electronics inside it, presumably due to its having been mounted above a translucent panel in a suspended office ceiling. For the cover I used stiff plastic sheeting glued around the flat rim on the fitting's front.
Below, if you look carefully, you can see the fitting operating with its plastic cover (note that the left-hand tube is not so yellow in real life; this is an artefact brought about by the 100Hz ripple of the tube's light output):
Below you can see the 3-pin IEC connector attached to the fitting for mains power:
This fitting seems to give a good level of light output and does not flicker to the naked eye. The magnetic mains-frequency (not electronic) ballast works very well and indeed such units are known to outlive their electronic counterparts, albeit at the cost of a slightly lower efficiency.
The fitting also contains a capacitor. This is meant to be for power factor correction (whether the current draw is synchronized with the voltage on the mains sinewave). A unity power factor (the optimum type) would be important for commercial lightning since a corporation may be fined by a power company for having too low a power factor.