If you can keep the required step rate within reason, the LPT port works fine for industrial stuff. If you need to go fast, there are cards that can increase your step rate obviously and for low cost. If you already have analog only drives then the solution is to go with analog interfaced servos obviously. But the number of machines being controlled via step and direction is huge, especially for low end machines which is what I think you are talking about. I do not consider Mesa cards to be expensive, but perhaps your machines are very inexpensive.. so then it becomes a "relative cost issue". Also, the more you buy the cheaper they get. If you don't need speed and high power, most of what you need can probably be done with stepper motors. Less than 200 watts is stepper motor territory.
Using an LPT port with a stepper driver and motor is about as inexpensive as you can get for motion control. If you need more power, you can move up to a step and dir interfaced Servo drive. Dave On 4/2/2013 4:23 AM, andy pugh wrote: > On 2 April 2013 09:19, propcoder<[email protected]> wrote: > > >> The question is: which way to go? >> > I guess there are two ways to do this, either choose the optimum for > each application, or try to find one technology which fits all > applications. > > The latter approach is likely to be a lot more expensive, but does > have the advantage that upgrades will simply involve bigger motors > and/or bigger drives and no changes to the control system. > > >> 1. Take AC servo motors and drives like Yaskawa, Panasonic, Delta >> electronics, add gearboxes, tune PID, use position control mode using >> LPT and step/dir. >> 2. The same as 1, but with mesa card and velocity control mode, position >> loop in LinuxCNC. I think this way is logical only where trajectory >> following needed. >> > I don't think I would consider using the parport in an industrial > setting. However I might be tempted to use step-dir servo drives with > internal position control for the more undemanding applications. > If all that is needed is for something to go to a position, then a > Limit3 and stepgen is easily controlled direct from HAL. > > >> As for the 5th, I think it is possible to use a bridge, make PWM >> frequency booster or serial-in to PWM-out controller with current >> limiter and encoder counter with serial shift-out interface. >> > It is possible to control a 3-phase inverter bridge directly from a > Mesa card, the three-phase PWM generator and the HAL bldc component do > all that is required. > However, I doubt it makes sense to install home-brew drives in an > industrial setting, especially if the plan is to install, get paid, > and walk away. > > ------------------------------------------------------------------------------ Own the Future-Intel(R) Level Up Game Demo Contest 2013 Rise to greatness in Intel's independent game demo contest. Compete for recognition, cash, and the chance to get your game on Steam. $5K grand prize plus 10 genre and skill prizes. Submit your demo by 6/6/13. http://altfarm.mediaplex.com/ad/ck/12124-176961-30367-2 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
