Messages

6961

General Mach Discussion / Re: add relays to Break out board schematics

« on: May 31, 2017, 11:31:59 PM »

Hi
correct in what sense...it will not work for a relay. The 4.7k resistor permanently powers a relay coil if hooked to
an output and the phototransistor shorts the coil...all for what?

Craig

6962

General Mach Discussion / Re: Question about lost steps and CPU cycles...

« on: May 31, 2017, 08:44:40 PM »

Hi,
kool, still wouldn't attempt the surf the net while machining tho...

Craig

6963

General Mach Discussion / Re: My second build, advice please, Mach3 vs. Mach4

« on: May 31, 2017, 06:33:19 PM »

Hi,
yeah, given the age then analogue is highly likely.

There few manufacturers of analogue capable controllers, all however in the $1000-$1500 bracket.
Given,say, a couple of Delta 750W servos and drives can be had for the same or even less than an
analogue controller...with consequent 'new' reliability and repair/replacement so much more
achievable than repairing analogue dives/servos....

Craig

6964

General Mach Discussion / Re: add relays to Break out board schematics

« on: May 31, 2017, 09:49:33 AM »

Hi,
measure the voltage across R1 with the buffer amp output high, do the calculation to find the current thru R1.
Most optoisolators have approx. unit current gain across the opto boundary. Thus if you have 1mA input thru the photodiode then the
phototransitor will have  approx. 1mA in emitter/collector circuit. Most PCB relays will need 20mA for reliable operation,
ie you should aim for 20mA in the photodiode.

Another possibility to increase the sensitivity of the phototransistor is to bias the base. It is for this reason that the base is
pinned out. Use a resistive voltage divider to apply 0.55-0.58V or so to the base. If you bias to high or circuit conditions change,
temperature for instance, you risk having the phototransistor conduct WITHOUT the photodiode conducting!

Craig

6965

General Mach Discussion / Re: add relays to Break out board schematics

« on: May 31, 2017, 05:24:24 AM »

Hi,
what voltage do you have available? Clearly the 74HC********* has to be 5V and so also the input photodiode of the optocupler.
The relay and the phototransistor don't have to be 5V, in fact better to be 12V or even better 24V. Relays are available with
5V coils but they are pretty small and liteweight and not likely to last long switching 230V to a pump. There are many more 12V
relays and due to industrial use thousands of 24V relay to choose from.

Craig

6966

General Mach Discussion / Re: Question about lost steps and CPU cycles...

« on: May 31, 2017, 04:40:01 AM »

Hi Adam,
I used parallel port for some years but found as you have UNDER NO CIRCUMSTANCES attempt to run any other software while machining.

A little while ago I bought a SmoothStepper ESS and it works a treat and is very much less sensitive to CPU load but guess what, UNDER NO
CIRCUMSTANCES do I run other software while machining! Someone on the forum described the situation 'when a personal computer is hooked
up to and controlling a machine it is NO LONGER a PC, it is a machine controller that happens to use Windows Operating software'.

You have been lucky in that you've only lost steps, wait until you have a serious crash because the machine lost the plot because you were
doing something else....

Craig

6967

General Mach Discussion / Re: add relays to Break out board schematics

« on: May 31, 2017, 04:21:33 AM »

Hi,
it worked!  The protection diode Tweakie talked about  is D1. You don't really need a resistor in the output circuit, the relay coil is commonly
1kohm and will self current limit.

Craig

6968

General Mach Discussion / Re: add relays to Break out board schematics

« on: May 31, 2017, 04:15:29 AM »

Hi,
don't know whether this will attach....

6969

General Mach Discussion / Re: add relays to Break out board schematics

« on: May 31, 2017, 03:45:29 AM »

Hi,
I don't think your diagram is correct...the relay coil is permanently energised as you've drawn it.

The relay coil should be in series with the optotranistor, commonly in the collector side.

Craig

6970

Mach4 General Discussion / Re: USB gamepad as jogging device

« on: May 31, 2017, 03:38:30 AM »

Hi Thom,
really really good addition fpr making circuit boards.

I made one about three weeks ago about 60x80mm with regular 35um copper. I 'etched' to a depth of only 50um and got
perfect isolation across the board and that was with TSSOP ICs, 0.3mm between the pads. Never been able to get such fine
detail until I started using Autoleveller.

Craig