A lot of good, useful comments, thanks!
Mainly have been purchasing "Plug & Play" leds, first in flash light applications, but later also the house lighting has been converted to LED light, guess my home lighting is now 90 % converted to led. The winter here is long and dark, and the kids seams to make a sport of leaving all the lamps permanently on needed or not, home or out....so converting to leds is one way to reduce the electric bill(but at a cost off course).
Branded ones (Philips, Osram ..)are extremely expensive but on the other hand the quality of some of the stuff from DX.com is pretty bad. The tint of the led is pretty important(for home applications I use only warm white), also using correct Wattage(hig enough) for the each spot is critical for a comfortable nice light. Most halogen transformers will not work well as a LED PSU, need to swap them for specific led drivers so that is also one thing to consider.
Recently have found good led's on both Amazon.uk and ebay.uk. For time been, SMD leds has the best price/lumen ratio, however they works best in applications where indirect light can be used.
The idea of playing whit led chips come after a purchase of a 10W SMD LED Floodlight. Plenty of light, no heat and a very low power consumption at a reasonable cost. Planning to install 6 of those in my garage as working light.
Yes, single leds was the initial topic, almost like like these:
1p 10W Warm White High Power Bright 900LM LED Lamp SMD Bulb Chip 9-12V DC AR | eBay
The high power smd chips are priced reasonable when sold as bulk, so it does not matter even if will destroy a few...Now there is a new type called COB leds, I am waiting for first delivery. For the home made stuff don't yet have such specific applications, will test and see what comes up.
DC, Volt, Amps, Watt stuff is somehow within my comfort level but regarding ohms, diodes I am on thinner ice so will be in troubles regarding anything that does not run on constant voltage. But hope to learn more and get help from various forums!