More Light!

Well, the lamps in the kit are fine in their own way (once equipped with inline switches; 1.19 from Wilko, and extension leads) but I need something more.

I’m thinking of modifying a readily-available table lamp. This will look nice! There are three ways I could proceed with this.

Firstly, I could build an inverter to run an ordinary compact fluorescent lamp from a 12V supply, and house this in the base of the lamp so it just has a lead with a 6.3mm. jack plug to fit my distribution boxes. The requirements aren’t as exacting fot compact fluorescents as for some appliances, because eco-bulbs already contain their own switched-mode power supply and will run happily from about 200 volts. It can even be AC or DC; though since cheap diodes are used, high-frequency AC will need rectifying before it gets to the bulb. The advantage of doing it this way is that I can replace the bulb with a standard component anytime. The disadvantages are that there are two stages of power conversion, each with inevitable inefficiencies of their own — and 80% of 80% is only 64%; and I will be limited in the range of donor lamps I can choose. There has to be room in the base for the electronics, obviously, and it has to be capable of accepting a compact fluorescent — many cheap table lamps have 14mm. screw fittings. And though 14mm. screw-in eco-bulbs do exist, an awful lot of these cheap lamps have the shade set wrongly for them.

Secondly, I could build an inverter to run just the tube element from a compact fluorescent lamp from a 12V supply. This will increase the overall efficiency of the system, and again there will be room for it in the lamp base. The disadvantage is that it will require heavily modifying the bulb (ripping out all the existing electronics and wiring straight to the cap) and choosing a suitable donor lamp.

Thirdly, I could build an LED “bulb” with white LEDs and ballast it to run from 12V. This looks like the easiest way to fit it to any existing lamp base and shade. In this case I will have to use one with a screw-fitting lampholder, as this is polarised. At the kind of currents I will be shoving through my diodes, it’s vitally important that the connections be right. LEDs behave like zener diodes and break down somewhere between 5 and 6 volts, as opposed to the usual forward voltage of 3.5-4V for a blue or white LED; which means that they will be dissipating more power. And I already want to run them right on the verge of meltdown.

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