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Messages - jimpinder

691
General Mach Discussion / Re: Lathe motor question "Variable Speed"
« on: April 19, 2008, 06:35:55 AM »
I will suggest the alternativeĀ  - which isĀ  - replace your spindle motor with a three phase motor (about twice the power) then use a single phase to 3 phase inverter to control the speed. PWM and M3 and M4 signals are readily available from Mach 3.

I say "twice the power" becasue you do loose torque at lower speeds with an inverter - but I am assuming you have a gearbox on the Harrisson

I only say this becasue I've done it, and I know Hood has done the servo option - the choice is yours.

692
I cannot understand say your Campbell breakout board has no provision to take signals from the Geckos. It must have some input lines to the computer - pins 10,11,12,13 and 15 - unless you are already using them all. Al you need is one of these and configure it on Config/Ports and Pins/Input. It doesn't matter what Mr Campbell says the inputs are for, you can use them for anything.

I do not think the Gecko pins should be tied high. The Gecko spec shows a neat way of using a sprung loaded switch, to momemtarily switch 0v or 5v to the inputs, which I though would be ideal and keep you in control of the situation. I would install this, even if it means manually enabling the axis before you start. - At least the Geckos would not reset themselves automatically.

Whilst I understand the photodarlington system you are proposing, is there not a spare input line, or can you re-arrange your limits onto one line, so that you can trip the E-stop input on Mach3 - this would be much better than artificially triggering a limit, becasue you can reset immediately.

Yes - you will need some sort of delay on start-up - which, I assume requires a 5v signal onto pin 5  - to switch the drives on. You could, of course drive this from the computer, using a brain, or vis basic script to an output pin. I don't know if the Campbell boards provide isolation and a bit of applification on the output pins, but that seems the simplest way to me.

693
Are you following the wiring diagram shown on the Gecko website - in respect to pin 5 output from the drive.

This, it would seem, is multi functional and has to have a sprung switch so that it can be triggered to +5v  to reset the drive if a fault osccurs. It would then seem that the output from that pin stays at 5v, until a fault occurs - at which time it reverts to 0v.

I would suggest that all you need is a connection from the 3 drives to a Mach3 input. This could be to a limit switch input, or to the E-stop input, which would stop Mach 3. The connection should be made from pin 5 of the drives in parrallel via a diode to the input, so that any one of the drives switching to 0v passes the signal to the computer input. Because of the diodes, there is no feedback to the other drives. Any signal diode would do.

If you have the Geckos wired up via their enable switch, then Mach 3 could "disable" these lines to stop all movement. It stops "step" and "dir" signals anyway.

694
General Mach Discussion / Re: How to wire steppers???
« on: April 16, 2008, 01:51:44 PM »
I've got to thank you guys for all the input to this post - which I will admit, I never thought would get this far.

Yes - I am a bright chap and can understand all that has been said, and realise it is far more complicated that I have made out.

I think the post ought to close now. In the end my system will work and be reasonably efficient and fast enough for me.
BUT

The main thing I was worried about  are the vast number of motors and drives that are kicking about our hobby - and the "starters" or "newbies", with little or no experience, have no idea what to use.

It would have been nice to get to a point where we could say - yes - for this motor, use this drive set at this current, at that voltage.
I suppose that is a little pie in the sky.

Again, thanks again - Ian - don't bash your head against the wall - I'm not that bad. :o

695
General Mach Discussion / Re: increase the feed (accelerando)
« on: April 16, 2008, 01:30:08 PM »
Now I understand - make sure you are set on Constant Velocity for this.


696
General Mach Discussion / Re: Datum Zero
« on: April 16, 2008, 12:25:40 PM »
I assume that, once he knows what height his cutter is at, he can use offsets on his tool table - over to you Guy Gibson !!

697
General Mach Discussion / Re: Manual Tool Change
« on: April 16, 2008, 12:13:29 PM »
If you watch the Video Tutorials there is a program on "Scripting" which covers this exact problem.

The M6 script can be altered to do precisely what you want - in other words - move to a preset location and wait til you have reset the tool. You can jog the tool up and down onto a plate or measure or what ever, change the z axis offset and resume.

The script is in Visual Basic and is fairly easy to learn - if you know any of the programming languages, and the scripts themselves can write GCode to move the mill directly.

I have this on my lathe (slightly different command but) - the tool away from the work, I change the tool and the tool number changes which brings into effect the new tool offsets. I have a quick change holder, so my tools and offsets are all preset - but that is something for you to think of in the future.

698
Looking again at the diagrams - are there any controls on this - in other words, how can you control it now ??

I can see a slot for a parrallel port - what is that for.

699
I think Hood has put the problem simply - I assume the equipment you have got, when it is all put together, will drive your motors - and hence the mill.

Mach3 is NOT a DRIVER - it is a controller - so the question is, when you get it all together - what makes it work - in other words - what signals do you need to put in to make it go backwards and forwards.

It is unlikely that the bits of your system will be all in one. There will be a seperation some where, between the computer that did all the calculations for the system and told it what to do, and then the driver side - which took those signals and converted them into movement.

That is the point on the system you need to find.

Mach3 provides - for each axis - three wires - a "step" wire, a "direction" wire and a "return signal" wire ( the return signal wire might be common to all axis - therefore it might appear as only two wires per axis, plus a common).

On the "dir" wire, Mach 3 puts out a +5v or 0v signal  dependent on the direction the axis is to go, and the "step" wire puts out a +5v pulse (or a 0v pulse - it can be altered) the frequency of which is dependent on the speed of the axis, and the number of pulses drives the axis a set distance (on mine 48,000 pulses = 1 inch or movement)

This is the basic system Mach uses - so unless you can find a place where you can input step and direction pulses, you are a bit stuck.






700
General Mach Discussion / Re: Datum Zero
« on: April 16, 2008, 03:56:05 AM »
This is british genius at it's best. During the last war a chap called Barnes Wallace invented a bomb, which when dropped on water, skipped across the surface, until it hit the dam wall. The bomb then sank to the bottom of the wall and exploded - blowing up the dam - hence the name DAMBUSTERS.

The R.A.F. squadron who made the attack had the problem of dropping the bomb at low altitude, at night, at a precise height. The squadron leader was a bit ***** one night and went off to the theatre. There he saw spotlights on the star artiste - and realised that two spotlights at an angle only coincided at one point - and spotlights were fixed shining at angles from the nose and tail of the aircraft to meet under the aircraft at the precise height the bomb had to be dropped from.

Watch the film - if you can find it - Stiff upper lip and all that