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Relay for TTL signals?
« on: October 24, 2010, 10:08:47 AM »
I’m switching my plasma machine software to Mach3. I have a stand alone torch height controller that sends 5V TTL step and direction pulses to my driver while the torch is active. I’m using a cheep Radio Shack double pole double through relay to switch the Z signals between software and height controller. It appears to be working fine. Is there a better relay for TTL switching or is some kind of solid state switching better? And if so could you send me the info. Thanks for any help.

Tony

« Last Edit: October 24, 2010, 10:10:23 AM by Tony Bullard »

Offline stirling

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Re: Relay for TTL signals?
« Reply #1 on: October 24, 2010, 11:32:55 AM »
Hi Tony - I've done this in the past using logic gates - and / or / nor whichever is best suited for your purpose. A question though, when the cut is over and you hand back control of Z to Mach - how do you tell Mach where the Z is? What I mean is: suppose you started cutting when Mach knows Z is at (say) 0. Then, at the end of the cut and because of warpage, the steel is actually higher, say at Z=10mm. When you hand back to Mach, it thinks Z is still at zero - etc. if you see what I mean.
Re: Relay for TTL signals?
« Reply #2 on: October 24, 2010, 02:45:39 PM »

Good question Stirling. One thought I had was to have an adjustable Z+ limit switch which would be set to a safe distance above the work for movements between cuts and after returning to Mach go to that limit and reference Z or “SetSafeZ”. These would be macro calls. The torch is a floating head with a Z- limit switch. I thought I’d use that to establish torch height along with some code to set a pierce height. Any thought would be a help. Any schematics for the logic gates would also be helpful. Not my strong point.

Tony

Offline DaOne

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Re: Relay for TTL signals?
« Reply #3 on: October 24, 2010, 06:02:00 PM »
How about using a simple opto isolator?
Re: Relay for TTL signals?
« Reply #4 on: October 25, 2010, 07:46:10 AM »

Thanks DaOne, The opto isolator and the logic gates are over my head. I’ll have to get some help with that. Another thought I had was to take the direction signal and the “move” (before it gets to the pulse generator) signal from the height control and somehow inputting them into Mach to control the Z while in THC. I don’t know if a ModBus or something could handle the speed. I don’t think macros could.
Re: Relay for TTL signals?
« Reply #5 on: October 25, 2010, 12:24:45 PM »
i am using relays for thc up and down signals. have not had a failure yet, been using them for 4 years now.
Re: Relay for TTL signals?
« Reply #6 on: October 25, 2010, 12:38:16 PM »
i am using relays for thc up and down signals. have not had a failure yet, been using them for 4 years now.

are you use DC motor for Z axis ?

Amir
**Even a clock that does not work is right twice a day**
Re: Relay for TTL signals?
« Reply #7 on: October 25, 2010, 09:29:20 PM »
rutex thc. have had it for about 10 years. after changing to mach3, using the dc + - to switch relays to send signal to mach. gecko 212

stepper motor on z axis. the rutex would have worked okay by itself to a dc gearmotor, but tended to dive during cornering .
Re: Relay for TTL signals?
« Reply #8 on: November 05, 2010, 08:51:16 AM »
Tony,

You can find some relay options here: http://www.cnc4pc.com/Store/osc/index.php?cPath=24

If controlling relays with mach3, it is better to use a breakout board that does come with relays and a safety charge pump, like the C11G: http://www.cnc4pc.com/Store/osc/product_info.php?cPath=33&products_id=46

Arturo Duncan
http://Http://cnc4pc.com