First of all, thank you very much to you two (Paul & Unit). Belive me if I say that some times I do regret not being a native english; I'm pretty sure I'm missing some subtleties (Is this correct?).
A AM motor speed controller... sounds really frightening :sweat_smile:. it is just an . . . . .. AC drive. (Maybe the heat wave in Spain -38 ºC outside- has something to do).
The AC drive the guy is using has an input that ranges from 0 (stop) to 10 V (full speed). For the moment I have suggested him to solve the problems one by one: to get it working in "manual" position and, then, controlling the whole system by means of the arduino. The "automatic cycle" he intends is pretty much like an old washer machine one: clockwise slow, counterclockwise slow, then medium, then centrifugate, . . . ., so I've told him to concentrate in the hardware first as the code is not going to be (I guess) difficult.
I've been working with a "due", so one possibility is to use one of the DAC's to generate a "quasi-continuous" signal (as Unit suggests). The other possibility I asked to myself (and to the forum) was to filter a PWM to get 0 - 5 V (The DAC the due uses spans 4/6th of the 3.3 V: 0.55 to 2.75 V).
Then the matter of doubling the range: I have a nice experience on electronics . . . that hasn't been renewed from the '80s!! (except for what I've read in the -this- forum along the last year). Although a lot of the, say, "discrete components" electronics (I include in this concept op amps, the ethernal 555, small TTL & CMOS circuits, . . . ) keeps being the same (much cheaper), I feel confused sometimes (I find nowadays things like 3.3 to 5.0 V level shifters -yes, I know they ARE NOT for continuous signals- that didn't exist then . . . ). For that -doubling the signal- purpose I'd have designed in the past a simple op amp (uA 741) circuit with a simmetrical (+- 12 - 15 V) supply to convert from 5 - 0 V (inverting "by software" in the arduino) to a 0 - 10 V. I'd need a double power supply and I remember adding caps (as the Texas Instruments handbook instructed to do) to make it stable for a continuous signal . . . . It needs a bit of soldering & skills that my "pupil" has not. That's what I asked for a "prêt a porter" solution . . . . .
(I hope having overcome the heatstroke and explained myself this time . . . . :sweat_smile:.)