question from a beginner

skenny · Jun 17, 2011

Hi,

I working on a project on my farm and have been having troubles finding answers so I thought I would start asking some experts.

I would like to find a PLC that has an LCD display, around 4 buttons and a couple of analog inputs all contained in a module that can be used outdoors.

I am a begineer with PLCs so hopefully if what I am looking for exists, it would not be to hard to learn the programming.

Any suggestions of where I can find such a device?

leitmotif · Jun 17, 2011

What do you intend to control? More details get you better help and answers.

iant · Jun 17, 2011

Also what is your budget and what do you need to control

There are so many systems available, when you add Analogue you increase the cost.

as Leitmotif has said - More Info Please

nonuke · Jun 17, 2011

I think they have what you need.
http://www.unitronics.com/Series.aspx?page=ProductOverview1

Mrslipmat · Jun 17, 2011

Are you looking for 0-10V, 0-20Ma, or 4-20Ma analog ? what is it for ?

JV

bkottaras · Jun 17, 2011

skenny said:
Hi,

I working on a project on my farm and have been having troubles finding answers so I thought I would start asking some experts.

I would like to find a PLC that has an LCD display, around 4 buttons and a couple of analog inputs all contained in a module that can be used outdoors.

I am a begineer with PLCs so hopefully if what I am looking for exists, it would not be to hard to learn the programming.

Any suggestions of where I can find such a device?

Horner XLe will work for you.
www.heapg.com

skenny · Jun 17, 2011

leitmotif said:
What do you intend to control? More details get you better help and answers.

Thanks for the response.

What I want to do is control the depth of my disk (piece of farm equipment used to turn over the soil). By using a potentiometer to know the depth of the disk, and a pressure transducer to know the pressure being applied in the cylinder, I can calculate the depth it is disking. I would like to take these analog inputs from the potentiometer and pressure transducer, bring them into the display to go through a few calculations, and be able to display the depth. Also via the display, I want to be able to enter a depth, and I would adjust the disk manually until it reads out what I want. And it also has to be a bit weather resistant because I want to use this on a tractor.

I hope this helps explain what I am looking to do.

Ron Beaufort · Jun 17, 2011

what will the range (inches) be on the disk movement? ...

what type of resolution are you shooting for? ... is plus or minus 1" OK? ... plus or minus 0.25" ... etc.) ...

I'm wondering if a potentiometer is going to give you the input signal you'll require ...

have you heard of Temposonic? ...

http://www.mtssensors.com/products/index.html

Tom Jenkins · Jun 17, 2011

I'm guessing this is on a three point hitch?

I'd say either the Unitronics or the Horner. I've used the Horner ( http://www.heapg.com/Pages/Products/products_OCS_X_xle.html ) and the pricing is good and the programming is straightforward.

skenny · Jun 17, 2011

Ron Beaufort said:
what will the range (inches) be on the disk movement? ...

what type of resolution are you shooting for? ... is plus or minus 1" OK? ... plus or minus 0.25" ... etc.) ...

I'm wondering if a potentiometer is going to give you the input signal you'll require ...

have you heard of Temposonic? ...

http://www.mtssensors.com/products/index.html

Thanks for the reply.

I had planned to use a rotatary potentiometer to measure the angle between the frame and the lowering cylinder.

As far as resolution, I would like to be able to be accurate within 1/4 inch if possible.

skenny · Jun 17, 2011

Tom Jenkins said:
I'm guessing this is on a three point hitch?

I'd say either the Unitronics or the Horner. I've used the Horner ( http://www.heapg.com/Pages/Products/products_OCS_X_xle.html ) and the pricing is good and the programming is straightforward.

thanks for the reply

It would actually be for a pull type disk. I would use a rotary potentiometer to measure the angle between the frame and lowering cylinder.

iant · Jun 17, 2011

the angle can be done with a 'Chopped' Disk
this can go directly as an Input or two
Works like an encoder - no need for two analogues.
the pressure may be dificult what is the Width of your Plough.
as you know the soil varies - your idea may be too accurate.

do you have 24Vdc or 12Vdc available?

What type of cylinder is it - Hydraulic?

skenny · Jun 17, 2011

iant said:
the angle can be done with a 'Chopped' Disk
this can go directly as an Input or two
Works like an encoder - no need for two analogues.
the pressure may be dificult what is the Width of your Plough.
as you know the soil varies - your idea may be too accurate.

do you have 24Vdc or 12Vdc available?

What type of cylinder is it - Hydraulic?

thanks for the reply.

What does this "chopped" disk look like? Is there a website I can look at one?

The width of the disk is 22 feet.

The pressure is to know how much of the weight of the disk is being exerted onto the ground.

I would have 12 VDC available.

leitmotif · Jun 17, 2011

skenny said:
Thanks for the reply.

I had planned to use a rotatary potentiometer to measure the angle between the frame and the lowering cylinder.

As far as resolution, I would like to be able to be accurate within 1/4 inch if possible.

You can get cylinders that have position sensing built into them with resolution as fine as 0.001 inch. This may be a bit simpler and more direct measurement of angle using pot.

Pressure will tell you only force exerted by cylinder not position. May be handy to avoid tearing up your gear ie hit a rock or shallow dirt over bedrock?

Dan Bentler

Lancie1 · Jun 17, 2011

You can get cylinders that have position sensing built into them with resolution as fine as 0.001 inch. This may be a bit simpler and more direct measurement of angle using pot.

Good call, Dan. As and ex-farm boy and tractor driver, I know anything mounted on a disk needs to be as rugged as possible.

I know that soils vary, disks go up and down depending on soil hardness, smoothness of terrain, and air pressure in tires. Skenny, you will probably need an averaging routine in your program to calculate the depth, averaged over some time period (5 to 10 seconds). In many cases in the real world, it is not the instant reading from second to second that is of interest, but the average typical reading over some time period. Disking is not so exact that an average will not work, and an average depth will be much easier to obtain than an accurate instantaneous value.

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