Will it work

Hi, I am hoping someone can help me. I am in charge of a large grain drying and storage operation. We are adding another dryer. I am considering using some plc's but I am not sure what I need as far as inputs and outputs. I will be using proximity switches and rotation detection and speed sensors for inputs and I will be controlling motor contractors with the outputs.
Can someone help?

Thanks

elevator_dude said:

Hi, I am hoping someone can help me. I am in charge of a large grain drying and storage operation.

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In charge of...as in, owner? operator? plant manager? plant operator? maintenance technician?

elevator_dude said:

We are adding another dryer. I am considering using some plc's but I am not sure what I need as far as inputs and outputs.

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Not familiar with your industry. I would suggest you talk to your best operators, and other folks in your industry who are familiar with your stuff. There are a lot of member of this forum with vast experiences in many fields so I am sure you can get something from this thread, but I think you need a person on site to help you with identifying the I/O.

elevator_dude said:

I will be using proximity switches and rotation detection and speed sensors for inputs and I will be controlling motor contractors with the outputs.
Can someone help?

Thanks

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Yes, you will get plenty of help here, and it's quality will be in direct proportion to the level of detail you provide. I suggest lists, details, engineering units, pictures, more, much more info. Engineers don't like guessing or ambiguity, we like part numbers, exactness, and precision.

Paul

Hi!

Here are common IOs related to a motor control - what came to my mind an early sunday morning .

Inputs by the unit (motor).
- Safety switch (disconnecting the power lines, lockable)
- Local start switch (for testing)
- Remote control switch
Dependant on equipment type:
- Rotation monitor (belt driven eqipment)
- Overfilling detectors (between conveyors, elevator feeding)
- EStop monitor (for easier detection of which EStop switch to be reset)

Inputs in the MMC
- Motor protection (trip)
- Contactor feedback

Output, MMC
- Contactor control

Manual, Auto, route selection and group starts from the HMI.

Kalle

A lot of grain storage area is rated or classified as an electrically hazardous area due to the fire/explosion hazard from dust, typically Class 2, Div 1; or Class 2 Div2. The hazardous area rating affects devices and the wiring for those devices in the areas so rated.

The PLC itself is typically located in a 'safe' area.

Overfilling detectors (between conveyors, elevator feeding)

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I have done PLC control for a couple of grain dryers with storage bins. Level switches are need on each grain bin to detect when the bin is nearly full, otherwise you will dump tons of grain on the ground. I used capacitance-type high-level switches, two in each bin. If either switch showed a high bin level, then the PLC stopped the fill to that bin. You have to have logic to switch to the next empty bin, or an alarm horn that tells the operator to switch bins.

I will be controlling motor contractors with the outputs.

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Many motor contractors that I know would resent that!

What type of dryers do you have? Rotary of flat bed? Like Dan said you need to be concerned about XP (eXplosion Proof) areas.

No disrespect intended this is a potentially dangerous job. Be very careful.

Since you already have driers that presumably work, the first step is to look at the sensors and switches wired to their controls. Emulate what they are doing, and then start adding functions that the PLC can use to add value to the process. Find out from operators which kinds of "If only we could do....." things they would use.

Find out from operators which kinds of "If only we could do....." things they would use.

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Tom, this is a step that is often overlooked, but if it was done, there would be a lot of happy operators, and much fewer problems.

Lancie1 said:

Tom, this is a step that is often overlooked, but if it was done, there would be a lot of happy operators, and much fewer problems.

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Yes, and once the operators learn "that programmer dude can do anything", you will never run out of work, and make a lot of new friends. So often, the paradigms of the operators and even engineering managers are limited by what they have already seen.

They have very little understanding of what is actually possible, so they tend to ask for little things that, when combined into a bigger picture, often reveal a situation where the programmer can step back and say to himself, "They asked for this, and that...why?" and going further "If I give them this instead or in addition, it will encompass all of what they asked for, and also add features x, y, and z."

I find myself doing this for almost every request. Having started factory life as a grunt "production puke"* myself, I know the real human value in going above and beyond sometimes.

*I once worked with a group of arrogant managers (all engineers) who referred to the whole lot of us hourly slaves as "production pukes"...I told myself then I would never disregard the ideas from the folks who actually perform useful labor for a living.