As a driver for small motors you can use mcp14e4 or similars. And a small pic to communicate with. And if you don't need external mechanical activation, you can even use a simple digital potenciometer: http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=3D11026&mid= =3D10&lang=3Den&pageId=3D79 El martes, 29 de mayo de 2012, Denny Esterline escribi=F3: > I've not used _linear_ motorized pots, but the rotary ones I have used were > quite slow. Inertia and friction were basically non-issues. > The other detail is they had slip clutches so the knob could be moved > without the motor, this also acted to slip when the motor "hit" the end > stop. > > Yes, an H-bridge is a necessary driver. You can get these as a driver chi= p > (TI's DRVxxx series comes to mind) or do it with discrete transistors. > > For my money, PID is complete overkill for this application. i drive lots > of resistive feedback linear actuators with full ON-OFF control and a > deadband of +-2 ADC counts, never seen a hunting problem with that. > > Good luck. > -Denny > > > On Tue, May 29, 2012 at 10:10 AM, Josh Koffman wrote: > >> Hi all. >> >> Second email! As generally happens when I'm about to travel, I'm >> struck with all sorts of ideas I want to try out, and no time to do >> them. For now this will remain a thought experiment, but I hope to do >> some of the design while traveling, then build a prototype when I >> return. >> >> I've had an idea for a project that would use motorized faders. These >> are linear (slide) potentiometers with a DC motor attached. I've >> started reading about these, and apparently driving them can be a bit >> tricky. They have two resistance tracks, originally one was used to >> control your signal (audio or otherwise), and the second was used as >> positional feedback for your servo control. In essence these were >> linear servos. >> >> I'd like to drive mine digitally, as I'm going to be connecting the >> unit to an ADC input anyways. What's tricky is that there's a >> mechanical component to the design that needs to be taken into >> consideration, otherwise you stand the chance of having the fader >> yo-yo around as it "homes in" on the correct value it should be at. >> This is due to inertia and friction. In addition, you need to be >> careful about not slamming the unit into the end stops repeatedly, or >> trying to drive the fader if it's stuck (lest you burn out the motor). >> >> I'm thinking about an H bridge to drive the motor, and software to >> help with the positioning. I will also need to come up with some sort >> of capacitive touch sensor, as the unit has a touch path from the >> slider, and I'd like to know when it's being touched so as to disable >> the motor drive. >> >> I've never done any PID work, and I'm wondering if that's the correct >> route to go for the control. I've done some searching, but haven't >> come up with much for this particular application. Does anyone have >> any tips, or links to other documentation? I've been sent an >> application note from the North American rep for Penny and Giles, one >> of the most respected fader manufacturers. I'm working through it, but >> it's mainly based on analog control schemes. Still, useful stuff. >> >> Thanks! >> >> Josh >> -- >> A common mistake that people make when trying to design something >> completely foolproof is to underestimate the ingenuity of complete >> fools. >> -Douglas Adams >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .