> 1. no freewheeling diodes?

Small DC motors can be very noisy electrically. I'd be wary of EMF
interference to nearby logic

> 3. which component determines the base currents? the impedance of
> the driving source, or the ohmic impedance component of the LEDs??

As it was (IIRC, I saw it a couple of weeks ago) using a PICAXE,
then the max source/sink would be that of whatever PICs are used
as PICAXEs, 20-25mA. I guess that would be why Darlingtons

> 5. over which voltage range does this work? and for which brands and=20
> colors of LEDs? and over which temperature range?

Presumably a 6-pack of NiCds, and green (as can be seen in the photo)
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.