16
Technical support / Re:Help needed with new project.
« on: June 04, 2006, 04:11:23 AM »
Another common way of attaching rotary encoders is with a toothed belt and pullies.
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17
Technical support / Re:Help needed with new project.
« on: May 29, 2006, 04:48:03 AM »
No, don't use a linear encoder, they are way more expensive and use 5 volt differential signalling designed for servo controllers and precision readouts. You want a rotary encoder designed for PLC use. Attach it to the end of the screw adjustment shaft with a flexable coupling and lightweight bracket.
Contactors are ten times the price of relays so unless they are warn out I suggest you have an intermediate bank of din-rail mounted relays. I prefer this setup instead of having the relays on the PCB where they can be frustrating to fault find and replace.
That said, contactors are quite modular and if your ones are modern then you could replace just the coils with 24 volt ones. This may also apply to valves.
Indicators should be changed to solid state units for reliability. Limit switches are usually clean contact so will happily run on 24 volt.
Evan
Contactors are ten times the price of relays so unless they are warn out I suggest you have an intermediate bank of din-rail mounted relays. I prefer this setup instead of having the relays on the PCB where they can be frustrating to fault find and replace.
That said, contactors are quite modular and if your ones are modern then you could replace just the coils with 24 volt ones. This may also apply to valves.
Indicators should be changed to solid state units for reliability. Limit switches are usually clean contact so will happily run on 24 volt.
Evan
18
Technical support / Re:Help needed with new project.
« on: May 28, 2006, 05:27:07 AM »
opps ... best encoder would be a 12-24 volt unit. Make sure it's either a push-pull or NPN. PNP won't work with these PLCs, this goes for other sensors also.
Evan
Evan
19
Technical support / Re:Help needed with new project.
« on: May 28, 2006, 05:14:55 AM »
MD2424 to be safe on the I/O count and the MD-HMI for entering the lengths.
Evan
Evan
20
Technical support / Re:Help needed with new project.
« on: May 27, 2006, 05:07:13 AM »
The simplest solution is a smart relay. However, smart relays are not much fun to make regular adjustments with. The T100's will do a great job, especially with the measuring side of things.
Attaching a rotary encoder to the end of the feed shaft will give the required feedback for cut-to-length function. Go for a low resolution encoder of say 100 lines per revolution. You don't need better than that and a low performance controller like this often can't handle pulse rates above a few kiloHertz.
To eliminate backlash as a cause of error between encoder and material you should always reference the machine in the same direction of movement as when performing the measuring stroke.
Stay with ON/OFF switching for everything else. The T100 will have no trouble handling all the logic and timer functions.
The general approach for wiring is to have all limits and buttons and sensors go to inputs on the PLC and all contactors, valves and drives come from outputs of the PLC. This way you eliminate all logic from the electro-mechanical sections. Two benefits arise from this approach, one is ease of sequence modification and the other is clarity when fault finding. Exception is the human safety wiring if any is needed, this must be hard wired and verified to function correctly.
Evan
Attaching a rotary encoder to the end of the feed shaft will give the required feedback for cut-to-length function. Go for a low resolution encoder of say 100 lines per revolution. You don't need better than that and a low performance controller like this often can't handle pulse rates above a few kiloHertz.
To eliminate backlash as a cause of error between encoder and material you should always reference the machine in the same direction of movement as when performing the measuring stroke.
Stay with ON/OFF switching for everything else. The T100 will have no trouble handling all the logic and timer functions.
The general approach for wiring is to have all limits and buttons and sensors go to inputs on the PLC and all contactors, valves and drives come from outputs of the PLC. This way you eliminate all logic from the electro-mechanical sections. Two benefits arise from this approach, one is ease of sequence modification and the other is clarity when fault finding. Exception is the human safety wiring if any is needed, this must be hard wired and verified to function correctly.
Evan
21
Technical support / Re:Programming Help
« on: May 21, 2006, 01:32:49 PM »
Here's a hint, there is two parts to the job:
- Proceedure for transmitting SMS blips.
- Logic.
As you can prolly work out the logic is done with ladder and the proceedure is done with basic. The actual coding I'll leave to you for two reasons. One is because that's why you have been given the exercise in first place and the other is logic is always harder to think about than first appears so I'd just be providing an incorrect ladder program for you.
Evan
- Proceedure for transmitting SMS blips.
- Logic.
As you can prolly work out the logic is done with ladder and the proceedure is done with basic. The actual coding I'll leave to you for two reasons. One is because that's why you have been given the exercise in first place and the other is logic is always harder to think about than first appears so I'd just be providing an incorrect ladder program for you.
Evan
22
Technical support / Re:Access system
« on: May 08, 2006, 04:33:00 AM »
This is ridiculous. You should be on the phone asking for a support, not spouting off online - which is a rather slow way of asking questions.
Evan
Evan
23
Technical support / Re:MODBUS DATA ERROR
« on: April 15, 2006, 03:40:27 PM »
I haven't read this thread in detail so I maybe repeating a suggestion.
A 485 isolator is usually used at each field device in industrial environments simply for reliability, now and in the future, you never know when a machine is going to fault to earth and take every serially connected machine with it! I can't remember an exact price but prolly between $US50 and $US100 per unit.
Evan
A 485 isolator is usually used at each field device in industrial environments simply for reliability, now and in the future, you never know when a machine is going to fault to earth and take every serially connected machine with it! I can't remember an exact price but prolly between $US50 and $US100 per unit.
Evan
24
Technical support / Re:mcr on t100md-2424
« on: March 30, 2006, 12:51:13 PM »
hmm, the fixed font/code font entering isn't working too well on this site but I think you get the idea.
Evan
Evan
25
Technical support / Re:mcr on t100md-2424
« on: March 30, 2006, 12:42:19 PM »Code: [Select]
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[Terminal]--------------------| (MCR pin)
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| | 1k0 |
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\/
26
Technical support / Re:AMPMETER USING OP-AMP
« on: February 19, 2006, 09:33:34 PM »
There is two general ways to perform what you want. However, you won't be able to use such methods for AC frequencies above about 10 Hz due to the limited speed of the PLC. Your best line of attack for, say, mains frequency is to use an AC to RMS converter and then sample the resulting DC level.
Evan
Evan
27
General Discussions / Re:PLC Trafic light
« on: February 16, 2006, 01:22:25 PM »
I stand corrected. Any PLC is fair game it seems. 
Evan
Evan
28
General Discussions / Re:PLC Project
« on: February 13, 2006, 11:48:32 AM »
Heh, a Can Opener maybe? 
Evan
Evan
29
General Discussions / Re:PLC Issues
« on: February 12, 2006, 09:19:16 PM »
I don't get this. Why do so many people post questions on this forum about AB PLCs with no apparent association to TriPLCs?
Evan
Evan
30
General Discussions / Re:Mechanical vs Electrical Engineering
« on: December 23, 2005, 02:07:12 PM »
In other words, you will learn the ins and outs of ladder logic because you want to.
Electricians are the ones that are expected to know PLCs and electrical departments are the ones that get asked to do that work because of the wiring and specifications components. But programming PLCs are just as foreign and just as easy to learn from either field.
That said, you should get an electrical trade ticket and some work experence with wiring machinery, paying attention to how the parts interact on those machines, then move on to programming. This way you talk the same language as those on the floor.
A varsity degree will prolly take you off in other directions but if you are good with the theory then do 'em all. The more the merrier.
Evan
Electricians are the ones that are expected to know PLCs and electrical departments are the ones that get asked to do that work because of the wiring and specifications components. But programming PLCs are just as foreign and just as easy to learn from either field.
That said, you should get an electrical trade ticket and some work experence with wiring machinery, paying attention to how the parts interact on those machines, then move on to programming. This way you talk the same language as those on the floor.
A varsity degree will prolly take you off in other directions but if you are good with the theory then do 'em all. The more the merrier.
Evan