[sdiy] Varying gate lengths (using a monostable multivibrator) for a simple sequencer?

[harrybissell]

Hi Julian...

Julian wrote:

> Hello again,
>
> Ive been reading about 555s.
>
> Could i just run through my plan, in the hopes of having all my errors
> bought to light? ; )
>
> Trigger the 4017, probably from a roland 606's tom trigger out, via an LM358
> in order to give the 4017 the correct sort of voltages.
>
> Take the output from each individual output of the 4017 and pass them
> individually through the right type of transistor, to invert the pulse (the
> 555 triggers on the falling edge, not the rising, right?)

Yes.   If you couple the input to that transistor through a capacitor (with a
resistor
to ground) you will get a very short negative spike. This will trigger the 555
and stop you
from retriggering as well.

>
>
> According to the values of the variable resistor and fixed capacitor, the
> 555's output will go high for varied amounts of time.
>
> I would want a non-re triggering 555.  A re triggering one would not allow
> me to shorten the output shorter then the 4017s output, right?
>
> Would then put the 555s output through another transistor, resistor
> combination to set the output voltages to the desired level for the
> individual gate outputs.

The 555 would probably have enough drive for you to use a simple resistor
divider with no additional transistor (buffer) needed, unless you need to drive
a very large load.  I don't know what voltage you need for a gate... the 4017
AND
555 could probably be run from a power supply of the correct voltage so no
divider
is needed at all

If you want (let's say) a 5V output, run the 555 and 4017 direct from a 5V
supply.

> In this, a 555 and its associated parts would be needed for each step.

yes.

> Yeah, i know this is a real basic circuit for so many of you, but its my
> first venture into actually building something from scratch that's not a kit
> or just a circuit out of a book.  Any errors or foolishness being pointed
> out would be much appreciated.  Or, indeed, if I'm missing the point
> entirely. :S

I don't think you are missing anything. I'd try making ONE stage of 555 and get
that
to work, then just copy it...   Any problems will show up early.

If you make a schematic, you could post it somewhere and we can all take
potshots
at it. You'll get a lot of different opinions, and probably some good facts.
Usually if there
is an error, someone is bound to see it...

H^) harry