> "can you buy LEDs with inbuilt series
> resistors?", then the answer is, as he notes, "Yes, they are available, but
> the cost is relatively high for what you get
mmm lets see
5V 3mm LED: 20p (ex vat, in one off quantity)
standard 3mm LED: 4.5p (ex vat, in one off quantity)
resistor 0.6p

so the integrated unit costs about 15p more.  but the added conviniance 
when breadboarding or bodge modding is more than worth it imo.

The biggest problem I find with such devices is that there is typically 
no marking on them, so unless you keep very close track of them it's 
kinda tricky to tell them apart from regular LEDs
> 3.  Alternative not covered by Olin:    There would indeed by advantages to
> having a two-wire leaded optical indicating device (such as a "ballasted
> LED" that you describe) when prototyping and thereby not taking up extra
> termination points or having to run a nest of wires away from a port. This
> can be achieved easily enough by taking a leaded LED and leaded resistor
> (value of your choice) and soldering it to the LED in such a way that you
> get a 2 lead device which serves the purpose and which can be plugged into a
> "breadboard" as required. If you find these useful enough you could make up
> a number and keep them for test and development purposes.
>   
might be an idea, you would have to construct it very carefully and 
probablly use heatshrink to get a neat result. the last thing I want is 
something that creates even more sprawl of stuff over the breadboard 
making it even harder to get wires in an out of the required connections.

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