EASY MODS for the LED-strip Lamp

It is heartening to note that the LED strip lamp project has struck a positive chord with many hobbyists. Surely when compared with the few commercial products available at a steep price, the project is attractive both from the cost angle as well as from the ultimate saving one will make by way of reduced power bills.

Many had requested  the incorporation of a 'Hi-Lo' switching, so that the lamp could be kept on for dim 'mood' lighting and then switched to full brightness. I too thought this would be great, especially when  it is used as a 'wall-washer' or 'ceiling-washer' lamp above the TV.

Keeping to our motto of 'simple and easy', we will look at a solution. You might recall that 0.47 uF cap gives you about 47 mA current. Suppose you want to cut the current/brightness to half, go for a cap of 0.22 uF/400V, which gives you 22 mA. Please note that brightness and current do not have a one-to-one relation; the best way is to try various caps and then decide on "your brightness" and then wire that value in.

Incidentally, caps come in standard values of 0.47uF, 0.33uF, 0.22uF and 0.1uF.

Now for the Hi-Lo switching. Hunt around the electronics market and you are likely to get a mains-rated switch, either a rocker or more likely a slider, with a 'centre-off' position. If you do, consider yourself lucky and get that. Replace the original on/off switch with the new one. Look at the figure (A) and modify the wiring, and you are in business in no time!

Suppose you dont get a 'centre-off' switch? Go for a small rocker or toggle on/off switch, again rated for mains voltages. But this time you have to drill another hole or a slot near your on/off switch to mount this hi-lo switch. Wire it up looking at the diagram here (B) so that when the switch is closed, it adds a larger cap in parallel to the low-value one in circuit, which determines the low brightness. Please note that caps in parallel add up in value and so 0.1uF and 0.47uF will give you 0.57uF, pushing up the current to 57 mA.

The values I have suggested are typical ones. Surely they need some 'tweaking' and individual requirements will vary, depending on where you mount the lamp, the reflectivity of your walls/ceiling etc and your own 'level' of preferred low brightness. In the event that even with a 0.1 uF Low cap, you find that the lamp is bright, buy one more 0.1 uF of the same sort and put them in series. This will give you 0.05 uF and about 5 mA of current, but will push up the voltage rating of the 'total cap' to double that of the individual cap- a good ploy to prevent transient high voltages from 'eating' your cap.

I anticipate 'control freaks' going in for a multi-way switch and playing with a number of caps so that they  will have brightness levels that could be "dialled in" to suit any mood! Bravo to them, with the caveat that any switch you use should be capable of safely handling mains voltages.

Gentlemen, start switching...

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