[sdiy] TB303 Slide

[Mattias Rickardsson]

On 8 June 2012 17:56, Tim Stinchcombe <tim102 at timstinchcombe.co.uk> wrote:
>> How would it know that it came from 0 V and not 1 V?
>
> Because the initial step was *two* volts and not one, and it has been
> charging for 15ms, starting from 0V.

Where does it keep this information meanwhile? ;-)
The rate of change is just depending on the distance left to travel,
not on the momentary speed or what has happened before. (As visible in
the differential equation modeling the circuit with this exponential
decay as its solution.)

>> No, they both follow the same curve from 1 V on - the
>> exponential curve of the RC time constant in question. :-)
>
> Here is simulation output of the two curves:
>
> http://www.timstinchcombe.co.uk/synth/const_time_glide.gif

Good picture! Could you try delaying that red curve so that it starts
at time 18 instead of 0?

> As noted before, at any given time the gradient of the 1-2 curve (red) is
> always less than (actually half) that of the 0-2 curve (green) - you simply
> cannot 'drop' one on top of the other!!!

Not unless you move them in time, but then they'll fit. That timeshift
is the extra time that it takes for the long glide, in addition to the
time for the short glide. :-)

/mr