On 21 Mar 2008 at 11:51, [EMAIL PROTECTED] wrote: > Hi all, > > I have a followup question to my earlier question about adding > steppers to my setup. The (long-term) goal is to create a custom > toolchanger that will incorporate three steppers and three or four > relay-controlled widgets. > > If I was to add a second parallel port, I'm certain that I could "HAL > it up" to control the extra motors and such via gcode. However, based > on suggestions made by John Kasunich and others, it seems that isn't > the normal way to change tools. (It would be quite inconvenient to > have to insert lots of extra gcode in a program to spin the tool > carousel etc.) > > Apparently, a PLC (either hardware or software based) is > traditiuonally used for such purposes. It seems to me, though, that a > plc + ladder logic programming is capable mainly of sensing switches > and turning on and off relays...which is great if you have a > toolchanger that only needs to be told _when_ to change tools and > _what_ tool to use, but not how to physically spin steppers to > accomplish this. I would really like to be able to take advantage of > the kinematics etc. that EMC provides to move the extra steppers, but > it's looking like I might have to create a "semi-smart" toolchanger > that can be commanded with HAL+ClassicLadder.
Most PLC's (not relay output though) will have no problem creating a step and direction signal for your stepper drives. Some do the job easier than others. Even low cost $99 PLC's from AutomationDirect will give you a decent stepper drive pulse train. In the PLC's ladder you use the inputs from EMC to go to a spot, using binary gets you lots of choices in a hurry. With four inputs you could pick from 7 postions plus have a 'go' input. You will have to provide some scheme to home the changer and from there you just move so many pulses in the direction you need then lock it down... http://web1.automationdirect.com/adc/Shopping/Catalog/PLC_Hardware/DirectLogic _05/PLC_Units/D0-05DD for them that don't like to follow links DL05 CPU, 8 DC in / 6 DC out, 110/220 VAC power supply. 6K words total (2048 words ladder - flash, 4096 words V-memory), RLL/RLLPLUS programming, built-in RS232C programming port and additional RS232C communications port. Inputs: 8 DC inputs, 12-24 VDC current sinking/sourcing, 2 isolated commons. First 3 inputs are configurable in one of several high-speed I/O features such as 5kHz counter input, pulse catch input, or interrupt input (not available when using pulse output). Outputs: 6 DC outputs, 6-27 VDC current sinking, 1.0A/pt. max., 1 common. 2 outputs are configurable for independent CW/CCW pulse train output or step and direction pulse output up to 7kHz (0.5A/pt.) (not available when using high-speed inputs). One option slot available for I/O or communication module. $99 John > > To summarize: > > I hope I'm wrong about this, but it seems as though I have to either > > a) control the extra three motors via gcode > > or > > b) construct an external device capable of moving the steppers by > itself and control device that via the PLC. > > Suggestions would be greatly appreciated. > > Thanks, > Pat ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
