[sdiy] CMOS 4516+4067 questions

[Paul Maddox]

Chris,

> hi Folks...I'm designing a 16-step Digisound compatible 16-step sequencer
> and have a bit of a dilemma about the CMOS side of it....I'm planning on
> using a 4516 counter to generate  the 4-bit code to control a 4067
MUX/DEMUX
> chip. THe way I'd figured out to do the CV channels was to have a 4067 for
> each set of 16 and to run a 51K resistor from +15 V to the common pin,
then
> have each demuxed output go to a 100K pot, thus getting 10V across the
pot.
> These would then all feed 100K resistors into an inverting summer, which
> would then feed to the main I/O board where another inverting buffer would
> turn it the right way round and send it to the oputside world......

yep this should be fine...
If you wanted to be really exact you could alwyas use a multiturn trimmer
driving an opamp (gain of 1, non inverting) which supplies
the 4067 common pin, so you can get EXACTLY 10v across each of the 100K pots
:-)

> First question...is this a right/sensible way to do it.....this sequencer
> could end up with 12 or more banks of 16 steps when finished (I want to
use
> it onstage), I didn't want to have 200 odd pots permanently powered, this
> way only one pot per bank at a time is drawing current ( I know it isn't a
> lot but 200 of them would be more significant), also the fact that ther
are
> resistors both sides of the 4067 should provide some protection in fault
> conditions......

SHIT, 200?
Thats a lot of knobs :-)

If you're planning on doing this I guess you're going to have a 'CLOCK'
module and a 'ROW' module...
one master module with the 4516 and the others with 4067's...
BTW, you could also use a 4024 (Damn I love those chips) instead of the
4516.

> Number 2....a 4516 will auto-reset when it reaches the end of 16 steps
won't
> it?....Daft question but it isn't addressed in the timing diagram in the
> datasheet......

yep, it does...

> Number 3: What sort of fan-out will I get out of a 4516?...I think I need
> five plus the buffers below on the main panel, will I get that OK?

1000's :-)
Cmos is much better for FAN outs the TTL..

> Number 4: If I use a TL074 to buffer the outputs will I be able to send
the
> four-digit output of the 4516 out to another board?

dont bother, if you get B version it would cope.
though I would include a quad AND gate on the input to each 'ROW' module (ie
each 4067)
just to keep the 4067 safe...

Also,
Why not use a uP?

Just a thought...

Paul Maddox
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