Messages

51

General Mach Discussion / Re: Need relay setup help

« on: September 06, 2008, 01:12:04 PM »

The easiest way is to drive the relays via a Darlington array, direct from your LPT1 port (or from your breakout board). A Darlington array is a power amplifier, and all the circuitry is contained in a 16 or 18 pin chip, which contains 7 or 8 seperate circuits. The cost less that £1 in UK from Maplin.

The circuits can each sink 1/2 amp and can be wired in parrallel to increase that. They take in a GND wire from your computer and a positive supply to drive your relays (whatever voltage you need). They are simple and easy to use, and do not need any additional diodes, etc.

What is the P/N of the chips you used I was looking at ULN2064 series quad drivers and wondering if they would work.

Kristin

52

General Mach Discussion / Re: hooking up limits

« on: September 04, 2008, 04:55:49 PM »

I just saw some fijutsu relays in a surplus catalog now I need go to their website and check the P/N as it has a different suffix than the ones on your catalog page. But they also have some others and all about $1USD ea or 10/$8.50 so it may pay to order up a bunch if they have gold contacts. They also had an inexpensive solid state contactor I could use direct for spindle control for $6.50 ea.

Kristin

53

General Mach Discussion / Re: hooking up limits

« on: September 04, 2008, 02:57:40 PM »

The outputs from Mach are through the breakout boards I have, one is a PMDX122 and the other a CNC Building Blocks Acustep, from there they go to the relay coils.
 The relays I have have gold plated contacts and so far no problems

Hood

Thanks,

That answered all my questions. Now for the relay hunt to begin!

Kristin

54

General Mach Discussion / Re: hooking up limits

« on: September 04, 2008, 02:26:17 PM »

I have used several methods, one is a board that cncbuildingblocks made, it is used on my lathe to convert the limits switch 24v to 5v, sadly Ed is no longer making his boards I also use relays to convert the 5v to 24v and vice versa. On the mill I am presently doing I made up a board with 7 relays on it, I can have the switched contacts of the relays either all in series, all seperate or a mixture of both just by placing jumpers accordingly. The idea behind this was I could connect a load of limit switches to the board and as the switched contacts were in series I would only need 1 input to Mach. I also have a similar one that takes outputs from Mach at 5V and has 24V accross the switched contacts, I use this for the Inputs to my servo drives which are 12 to 24V.
Hood

What sort of buffer/driver do you use for the outputs? Another thought (dangerous stuff this thinking!) way back I was building automated handling equipment with TTL logic, we used gold plated switch contacts on all our limit switches, one fine day our purchasing agent "got a deal" on a batch of microswitches that were silver plate, within a month I was running all over the country replacing 10-12 switches on every machine as the switches oxidized and were not working reliably. So that brings me to the relays, since there is so little current flowing I wonder if the contacts exhibit similar behaviours with out using some higher current by way of a resistor network and transistor or IC buffer.

Kristin

55

General Mach Discussion / Re: hooking up limits

« on: September 04, 2008, 12:10:28 PM »

I have 24V on things such as limit switches and then convert the 24V signal to 5V as near to the computer as possible and still have all the 5v signals shielded. The reason is the difference betwen Hi and Lo in a 24V system is much greater than a 5v system and so noise is hardly ever an issue.
Hood

Hood,

Very interesting can you post a schematic or description of how you do the 24v to 5 v ?

Kristin

56

General Mach Discussion / Re: parallel ports, serial ports, case fan cutouts..oh my!!

« on: September 03, 2008, 06:13:42 PM »

Dave,

Here is a dxf I just cut a female db25 cutout with, works great. I used a 1/8 mill cutter for everything, may need to edit as I was test cutting 1/4 lexan scrap.

Kristin

You guys are great, thanks again.

Here's a quick dxf for the 80mm case fan (in inches lol!)

Dave

57

General Mach Discussion / Re: After using the “Steps Per Unit” in “Axis Calibration” my CNC wont run properly

« on: September 03, 2008, 03:59:56 PM »

The square could be out due to backlash in one or both axis, when you generated/wrote the g-code did you offset for half the cutter diameter?

Kristin

58

General Mach Discussion / Re: Microstepping & Torque

« on: September 02, 2008, 09:15:10 AM »

Kristin, finding higher voltage lower capacitance might be easier and all you do is connect a few in parallel to get your required capacitance.
Hood

Yup,

Know all about that but getting BIG caps here is tough, the 30V/40surge is working and has not proved the "big bang" theory yet! Now to find another 10,000 or so Uf for Free!

Kristin

59

LazyCam (Beta) / Re: Learning Curve ahead!

« on: September 01, 2008, 08:50:56 PM »

see that 1.2 gig that windows reports is a dead giveaway.you got work to do.start looking for updates .you will probably have to flash your cmos.look for drivers and windows memory patches.
if it is a store bought computer and not a home built one.it will have a bottom of the barrell motherboard and a lot of paper that say's how great it is. Go get em killer! Kristin you might have two
memory strips in your desk computer pull one out and try it.

bill


Bill,

Well "problem solved" I think, Art Fenerty responded on the Yahoo site and suggested I zoom in on the character I was trying to offset and it worked perfectly! Still strange, wonder if it's screen resolution, video memory or what. But bottom line is it works, no problems with 1.26GB in my machine and it saved me pulling out the 256Meg strip for nothing.

Kristin

60

General Mach Discussion / Re: Microstepping & Torque

« on: September 01, 2008, 08:12:25 PM »

Ray, the calculator battery is fine it was me putting 1.1414 into it rather than 1.4141

Got it working short term, think I need a new battery for my cheap voltmeter too getting about 33VDC output with the cap connected, got to get the good meter out and find the new test leads I bought a few months ago.

I also got an answer on my LazyCam problem direct from Art Fenerty, seems zooming in before offsetting makes all the difference in the world! Two projects in one day is almost too much!

Kristin