[sdiy] Sequencer design

[Byron G. Jacquot]

>I've been investigating simple analog sequencer designs. These seem to fall broadly into two categories: The ones that have a whole load of pots wired between two rails, and use some kind of switch to select the appropriate output, or the ones that use some kind of switch (or logic decoder) to power up a single pot at a time.
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>Is there any advantage to one type over the other? Or a particular design which is regarded as a classic / reference?

I'd nominate anything built around the CD4017 as the "classic" design.  It's a sequencer on a chip - just add clock.  You can daisy chain them for more steps - there's a schematic in the datasheet.

To some degree, I think the different architectures reflect the technology of the time they were designed in - as logic chips became more prevasive, things settled into the two architectures you mention.  From a high-level black-box perspective, they achieve the same results.  I think the capabilities of the clock and counter logic are more important than the exact internal implementation.

Having messed with both both the multiplexed-output and one-hot input selection types, there's a pragmatic advantage to the one-hot selection style - you can use the selection output voltage to drive the "present step" LED.

-Byron Jacquot