As hinted during our earlier articles, the Picaxe range includes seven big brothers, grouped into 18, 28 and even 40-pin families. Although the baby "08" remains supreme for simple control circuits, it's rather like using a two-door hatchback for a cross country workout.

Consider the 18s as perhaps akin to 4WDs, 28s as Rally cars, while 40s. mmm - well you get the idea! The 40X is so long in fact that it looks like a toy aircraft carrier!

These larger devices, although featuring powerful further commands, still obey the key 35 "08" instructions, so all you've learnt so far can be immediately put to use - but it's obviously a waste to spend much more to just flash a few LEDs with them!

Although this month's coverage relates to the 18A, we've also shown a summary of the family overall (including the recently-released fire-breathing 18X). All enjoy the usual wide supply voltages (3-5.5V), 4MHz clock and direct ~20mA output drive but larger versions have dedicated Input or Output pins rather than the versatile I/Os of the "08".

Note that the basic 18 and 28 Picaxes, inferior to the "A" and "X" versions, are obsolete and no longer marketed. Incidentally, no "A" or "X" updates are planned for the "08" series.

Since Picaxes of course are PIC based, it's worth comparing the pin compatible 18-pin models with the ubiquitous PIC16F84 - now itself obsolete as replaced by the cheaper and more powerful 16F627 with an internal oscillator as well.

The enhanced PIC16F627 (the 16F819 - only released by Micro-Chip in January 2003), is the PIC that the "18A" (bootstrapped by Rev. Ed of course) is based on.