On Sunday 15 December 2024 03:12:22 pm wn4isx via groups.io wrote:
I was given some LED replacements for 4 foot florescents. They were defective from the factory, I carefully disassembled them, removed the stock SMPS, added a simple full capacitor feeding a wave bridge to drive the LEDs. I picked a capacitor whose capacitive reactance made the LEDs bright enough but they didn't get warm. 4 of them are roughly equal to 2 real florescents with no EMI. I bypassed all 4 diodes with low value caps.
Yea a lot of trouble but I was bored and my mobility was somewhat limited this summer.
I looked at those, briefly. IIRC you had to rewire the fixture to remove the ballast from the circuit. Those fixtures I mentioned came with bulbs that were rather mediocre, so I went shopping and saw some "high output" bulbs and ended up getting those, and that's what's in the fixtures now. Those LED replacements were around $20/bulb at the time, which struck me as a bit much. In the meantime I had picked up a 2-pack of reflector style bulbs to replace an outside light where I used to live, and one of those over my current work table gives plenty of light in there.
I've been fairly impressed with a lot of what I'm seeing out there using LEDs, not so much the regular light bulb styles but stuff that was designed for LEDs to start with. I bought a 10-pack of 10W LEDs a while back, and built a few lamps, using some little modules with 3 trimpots on them. I think that they were originally intended for battery charging, as one of those trimmers is irrelevant to my use. One is installed over my lady's desk, to replace the small incandescent fixture after she burned her arm on it, one is over my desk, and one over my radio gear. The two trimpots set the voltage and current. The LEDs I got are 3 chains of 3 in series (other ones put 'em all in series) so I set the voltage for around 10V maximum, and then set the max current to something like 300mA, meaning they're dissipating about 3W. Which gives plenty of light, and being 10W parts, they oughta last a good long time.
For some reason when I plug a small wall wart in for my desk light it pulsates several times before it settles down. So the one I'm using is an older one, with a regular transformer and bridge rectifier. Hers works fine on a switcher. I never did investigate why it did that, probably something to do with the design of the particular switcher I was trying to use. Having several large boxes of wall warts, I have plenty to choose from.
I'd like to come up with some simple circuit that would limit the output voltage and more importantly the current to drive these LEDs with, since I still have a bunch of them around...
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
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Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
