LED-based lightbulbs are getting more common and cheaper.
I propose a bulb that could be used as a spare for almost any situation in an emergency. The lamp would operate over a very wide range of voltages, AC or DC, would include a dimmer to set output level, and a set of adapters to fit a variety of standard and non-standard sockets: edison / mogul / bayonet / flashlight / 12V car headlights / clip leads / etc.
This could be achieved with a not-too-complex boost / buck switching power supply built into the bulb.
Cost: no object (it's for emergencies, remember!)-- csea, May 02 2013 3V/50mA http://www.cornwall...lbs.html#aG396_2e10 [pocmloc, May 02 2013] 230V/5.9A http://www.plasma-i...asma-i-products.htm [pocmloc, May 02 2013] I can count on no hands the number of times I've needed a replacement bulb (urgently or otherwise) but only had the wrong voltage bulb on hand.-- ytk, May 02 2013 [ytk] I'm sorry.-- csea, May 02 2013 I'm just puzzled as to what problem this is solving. Even putting aside the issue of matching bulb and receptacle sizes, it seems to me that the power consumption and output requirements for various types of bulb are so vastly different that plugging, say, a flashlight bulb into a ceiling lamp isn't going to be substantially better than simply using a flashlight in the first place.-- ytk, May 02 2013 It's solving the problem that csea needed a light bulb earlier today but couldn't find the right one. Some great halfbakery ideas have gotten started that way...-- DIYMatt, May 02 2013 Oh, well then bun for solving the problem admirably! (Even though I still am not sure what exactly the problem is.)-- ytk, May 02 2013 Perhaps a flashlight ("torch" in England) or lantern is what you need.-- Vernon, May 02 2013 [+] At least its an idea - more than can be said many of the recent postings.-- sqeaketh the wheel, May 02 2013 In point of fact, I was seeking to replace a 12V lamp with a bayonet connection on my boat, and didn't have any spares.
I have plenty of flashlights/torches, but wanted a slightly more than temporary replacement.
Even keeping supplies of CR2016/32, AAA cells, AA cells, C cells, D cells, etc only fixes the supply problem, not the 1.5V, 3V, 4.5V, 6V, 9V, 12V, etc, etc, problem.
I recognize the difficulty of replacing an 8' fluorescent lamp with something the size of a torch/flashlight, but this is the HB, after all!
Thanks for the comments.-- csea, May 03 2013 This bulb; that fits all sockets, and works on all voltages, do you have a design in mind or is this merely WIBNIFty.-- WcW, May 03 2013 Yes.-- csea, May 03 2013 Great, new alligator clips are on the horizon-- wjt, May 05 2013 random, halfbakery