How do I use an encoder to display length/distance

Hi all,

I have an application where I have a cut-off table that varies infinately in length from 8 feet to 16 feet. I need to somehow keep track of how long the cut-off table is +/-.025". I then need to display the length on a cheap LED display.

I am thinking an encoder, but I have only worked with encoders in conjunction with a profibus scanner(not a option in this case). I was wondering if there were some solution out there that would allow me to hook the encoder directly up to a display. Is there a LED display that can directly convert an encoder's square wave to a length? I have a feeling that would not work because I need to be able to scale/zero the display somehow.

So I need to somehow hook the encoder up to the AB PLC5/40. How do I do that? Is there some sort of encoder card specifically designed for this task?

Once it's in the PLC, I know how to get it to a display. Its just the interface to the encoder that I don't know what to do with.

High speed is not an issue, the table moves maybe 30"/min max.

Thanks in advance!

Just a suggestion!

You might give RED LION CONTROLS a look and see if they can help.
They have a line of very reasonable and versatile controls with digital readout.

I frequently work on some machines with a controlled shuttle motor.

They have a rotary encoder on the pulley sending pulses to an Omron counter. The counter reads pulses up to 99999 clicks, and can be scaled to read lengths. Also it can be set to activate an output at a preset reading (Overtravel limit?)

At start of each cycle, a reset pulse is sent to the counter to start the count 00000, and their repeatablity is very good - should easily meet your precision requirements.

Do you happen to know the model number of the Omron display? Is it a special display or are the features the display has common?

TIA

CSBC,
You also might want to consider equipment used on CNC machines. You could get a rotary or linear scale for your cut-off table. They also have 1 - 7 axis displays for readouts.
Something along this line...
http://www.acu-rite.com/act_Download.cfm?FileID=37&/microlinespecsheet.pdf

I dont know the exact Omron #, it is their 1.77" square size, with 2 inputs from the encoder. I search Omron & it appears to be a H7CR series

As i had to order & replace one - the encoder used is a Accu-Coder model 755A with Pull-Up output from Encoder Products This is a not off the shelf item, available with any pulse per revolution resolution you want (from 1 to 20,480 CPR)But use a small number, the shuttle I mentioned used 100CPR, and 24" of travel gave a count of 9100 clicks.

Unfortunately, the shop that has these machines is about an hour drive with no traffic (Sunday morning) 2 to 3 hours with normal Detroit traffic.

Hello,

If you don't want to re-invent the wheel, Here are some unit's used on saws all the time.

http://www.tigerstop.com/

Jason