Messages

591

General Mach Discussion / Stepper Motor Maximum Voltage

« on: March 30, 2015, 06:04:07 PM »

I don't think there will be a problem provided that you set the drive current to 1.6 amps or less.  I don't see where Stirling got 53 v from, it's not in the data provided afaics. 


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592

General Mach Discussion / Re: Hall Effect or Slotted Opto?

« on: March 29, 2015, 01:35:49 PM »

I'd have thought that it would be just as easy to connect the optical sensor, since the output circuit is much the same as a hall d=sensor, effectively open collector.  However, I've built a Hall sensor for my big mill for a tachometer, it uses a tiny neodymium magnet about 4 x 2 mm araldited to the spindle pulley, and the sensor "sees" it from about 5 mm away - so you dpon't need a big heavy magnet.  And just stick an equivalent weight bit of steel diametrically opposite to balance if it's a concern.

593

Mach4 General Discussion / New people welcome !! Come in here and introduce your self!

« on: March 11, 2015, 12:28:21 PM »

I am new to the board, and have a question regarding the use of Mach3 as a DRO.

I have long range plans to add control to my Harrison L5A, but for the present I would like to add DRO readout to the X and Z axis, and eventually to the tailstock and the compound. Is there a problem that I am not seeing using glass scales just as a readout without utilizing the many other functions of Mach3?

Thanks for helping

paul

Paul AFAIK Mach 3 will move the screws with a stepper or servo and it's DROs will tell you how much it's moving them, but it can't accept inputs from scales.


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594

General Mach Discussion / cam programs

« on: March 07, 2015, 05:57:11 PM »

Gsimple


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595

General Mach Discussion / USB or other Port

« on: March 06, 2015, 05:38:40 PM »

For what?  Only the parallel port gives enough i/o from a PC with good enough control over the signal timing to drive steppers accurately.  The trend now is to remove parallel ports from new PCs so they have to use either Ethernet or USB but these don't give control over relative timing on multiple hardware channels so you need an external motion controller.


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596

Mach4 General Discussion / PMDX-411 SmartBOB-USB in a DB-25 shell released

« on: February 27, 2015, 03:32:23 PM »

Cool!


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597

General Mach Discussion / Re: picaxe microcontroller input to parallel port in mach

« on: February 26, 2015, 12:40:21 PM »

1) If my picaxe is normally outputting 5V INTO the input pin on the BoB, and then it goes low, does that then mean that the picaxe is driving the input pin to 0V? Or does it mean it's left floating? I assumed the latter, as I thought a lack of output from a microprocessor output pin just means it floats around, not tied to 0V.

Yes, the picaxe pulls the input down to 0V, which is what you want.  Provided that a micro o/p pin is not tri-state, it is either at 1 (=5V or whatever the supply voltage is) or near 0 V.

2) Normally, inputs on my BoB are connected just to switches that act to ground the 5V that my multimeter tells me exists at the input pin. Having trouble getting my head around connecting inputs to anything other than switches; the idea of driving an external voltage into an input pin is a bit alien to me.

It's just standard practice.  That's exactly what the parallel port on your PC does, drive voltages from the PC into the BoB.  And the BoB does the same thing back to the PC.

3) If I'm driving 5V into the input, is that input then just held at logic high (5V), or is it held at logic high with 5+5=10V potential?

It's just held at logic high, not at 5+5.

598

General Mach Discussion / Re: picaxe microcontroller input to parallel port in mach

« on: February 26, 2015, 06:13:34 AM »

That's right.

Which pin only sources 6 uA?  That sounds very low for a digital output - in fact it sounds like the tri-state leakage.  The ideal approach would be a direct connection from the Pickaxe output (in enabled mode, not tristate) to the BoB input, with the Pickaxe code modified to drive the output active low.  If you can't change the code, then the (NPN) transistor inverter is an easy approach - probably a 47 K resistor from the output to the base; ground the emitter; connect the collector to the BoB input with a 10 K pullup to +5V.

599

General Mach Discussion / picaxe microcontroller input to parallel port in mach

« on: February 25, 2015, 06:03:36 PM »

I assumed that you were writing the pick axe code?  Then you just arrange to drive the output pin low to activate rather than high.  If you must use a hardware solution a single transistor inverter is cheaper and smaller than a relay and takes less current.


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600

General Mach Discussion / Re: picaxe microcontroller input to parallel port in mach

« on: February 25, 2015, 12:21:24 PM »

Is the power supply voltage to your BoB 5V?  If so, just connect the Pickaxe output to the BoB input.  You want to make sure the data bus is NOT tristated, so its levels are logic high or logic low, not something floating in between.  A relay is not a good way to do this IMHO.  Of course you need to make sure that the BoB pin you're connecting to is an input not an output - inputs don't have a "tristate".