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Author Topic: PWM as a digital information carrier (?)  (Read 3651 times)

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Offline Sweep

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PWM as a digital information carrier (?)
« on: March 09, 2008, 11:35:58 AM »
I am not even sure if I understand the title of this mail, so i'll try explain what I am trying to achieve.  ???

I have modified my Denford Triac ATC (bulit 1990) to have XYZ and spindle speed controlled by Mach 3 and it works great.
The Denford's main electronics are mounted in a slide out tray underneath the drip-tray, whilst the ATC electronics are mounted in a seperate panel. The two are connected together by two signal leads with a total of 3 wires (plus grounds). Two wires seem to carry the 'initiate tool change' and Fault signals, whilst one wire carries the information for which tool number is needed on the change.
What I am trying to achieve is to replicate this signal directly from Mach3 if possible, or, say, ModIO if that is easier.
I know Mach3 can generate a PWM signal as I am using that for spindle speed control, but can I programme this as part of a macro and change the 'on' and 'off' period' between each individual pulse to replicate the square wave signal currently being sent from the Denford? The smallest 'on' or 'off' period' I have measured on my scope is approx 0.1ms and the longest approx 0.5ms, with the full data stream taking around 150ms. The 'on' voltage is approx 11.5v.
I would really like to do it this way as the existing carousel toolchanger has pneumatic logic which looks after all the tool positioning and installing procedures, except carousel rotate, and all this is controlled by the existing system. To change all this would be a nightmare.

Any help would be greatly appreciated.

Thanks ...Sweep


vmax549

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Re: PWM as a digital information carrier (?)
« Reply #1 on: March 09, 2008, 12:23:37 PM »
Are you sure that it is not 3 wire rs232 serial communication??

(;-) TP

Offline Sweep

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Re: PWM as a digital information carrier (?)
« Reply #2 on: March 09, 2008, 03:19:21 PM »
It could be, but what's that  ???
How do I recognise if it is RS232 and does it make it easier to solve my problem? Can Mach3 speak this RS232 language.
If you can point me in the right direction to find out this info I would appreciate it as I am a Mechanical, not Electrical, Engineer. I have just bought myself my first oscilloscope (DSO) to try and sort the problem.

Thanks ...Sweep
Re: PWM as a digital information carrier (?)
« Reply #3 on: March 09, 2008, 03:51:32 PM »
Hi, A minimal "3-wire" RS-232 connection consisting only of transmit data, receive data, and ground, is commonly used when the full facilities of RS-232 are not required.


If you look to see where the wires go into the printed circuit board and look at the numbers on the ic chips, if one of them is labeled MAX232 or somthing similar then it will definatly be  RS232 communication.

The next problem lies in working out how to communicate with the board. This is really a task for someone experienced in electronics.

Mach3 can send RS 232 signals but apparently cannot recieve them.


Hope this helps.

vmax549

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Re: PWM as a digital information carrier (?)
« Reply #4 on: March 09, 2008, 05:31:54 PM »
You might want to try denford.com they do have a public help  forum up on the euro side.

Offline Sweep

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Re: PWM as a digital information carrier (?)
« Reply #5 on: March 09, 2008, 06:05:18 PM »
Thanks Vmax, but I am already a member of the Denford forum but they cannot help me.

I have had a look through the old manuals I have for the machine (downloaded from the Denford forum) and I think you are both right to suggest rs232. Have a look at the attached diagrams and you can see why it is not the easiest question for anyone to answer; they all seem to be rough hand-drawings! To make matters worse my machines ATC has serial number 001 so things would have probably have changed almost immediately.
A couple of things in my favour though, if you are correct about Mach only being able to send rs232 info, is that on picture 30.jpg I only have the green and red wires connected. These two wires give the square wave signal I was trying to descibe, with each tool having a different set of 'on' and 'off' periods.
I started to check the remaining three wires, shown on 'triac-toolchanger-link.jpg' when I had to stop for the family's evening meal but I should get them scoped tomorrow.
If these just give a constant 'run' or 'fault' signal then I guess we are in with a chance.

Thanks ...Sweep

vmax549

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Re: PWM as a digital information carrier (?)
« Reply #6 on: March 09, 2008, 07:17:55 PM »
Yep looks like rs232 to me. I would think you have a processor on board the tool changer that controls the mechanism and the 232 link is used to talk to and receive data from the ATC.

Mach should be able to send and receive via rs232 via the serial com port. Now the trick will be to know what protocol it will use and what the command structure needs to be. More than likely it will be straight ascii format or perhaps delimited ascii.

I will see what I can find out also to help you out. A manual for the ATC/machine might lead to a clue.

(;-) TP

vmax549

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Re: PWM as a digital information carrier (?)
« Reply #7 on: March 09, 2008, 07:25:11 PM »
Sweep I don't know if you have this yet.

But there are a lot of manuals on the denford site you may want to search through them to see if any can help.

Even manuals for the old DOS version.

(;-) TP
« Last Edit: March 09, 2008, 07:53:07 PM by vmax549 »

Offline Sweep

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Re: PWM as a digital information carrier (?)
« Reply #8 on: March 10, 2008, 04:19:11 AM »
Thanks for your support Vmax.
I am pretty sure that you are correct about the rs232 as the machine has a built in cassette player that uses rs232 for programming, and if this is correct then there must be a simple PC program for encoding this onto the cassettes in the first place.
I have a copy of the machine manual and more toolchanger circuit drawings that I have emailed directly to you. I haven't attached them to this post due to the number of pages. If anyone else would like to contribute to helping me please let me know and I will send you the files directly.

Thanks ...Sweep