Created Date: January 09,2005

Created by: Augusto

Just starting learning how to using PLC.

I have an application that requires a position indicator

for the main shaft of one small wire weaving machine.

The output is 0-360 degrees and the speed is less than 100 rpm. My idea is to slice 360 (One complete turn) by 1024,

use Grey code instruction to convert 16 bit gray code to BCD value and use boolean contacts to coordinates the events necessary to keep the weaving process going.

I have the 250 PLC and an absolute encoder (A/D) 1024 resolution but I am having hard time to find ways to marriage this two!! Any Help will be appreciated. Thanks.

Created Date: January 09,2005

Created by: Rich1955

Help me do the math 100 X 1024 is over 5000 right. The modulas won't count over 5k. The resolution of the incoder. The D2-CTRINT is 5k and the H2-CTRIO is 100K High Speed Counter Interface Module, 2 quadrature encoder counters up to 100KHz, or 4 single channel counters up to 100KHz, and 4 high speed discrete inputs for Reset, Inhibit, or Capture. Outputs supported: 4 independently configurable high speed discrete outputs or 2 channels pulse output control, 20Hz-25KHz per channel, pulse and direction or cw/ccw pulses.Are you saying 1024K. Is my math right? Look here http://www.plcs.net/downloads/

Does your Count have to be that close

Created Date: January 10,2005

Created by: Augusto

Nothing wrong with your math. MORE INFO.

Machine shaft - 4 " diameter.

One revolution - 360 degrees If I use 360 resolution absolute encoder, I will have a reference number for each degree. Encoder rpm will be close to 100 rpm. I have one absolute encoder with 1024 resolution (bit 0-9) Grey Code. For this machine, shaft position is very important. The spec. for this encoder: Max. Response frequency 20kHz, speed 3000 rpm or lower. What type (DL205) DC Input Modules should be used with this encoder? I have one D2-32ND3 24 Volts but the encoder output in not compatible. Thanks.

Created Date: January 30,2005

Created by: Ken regester

Use the Load Formatted command to load 1 to 16 bits from a location (X input) into the accumulator. Specify the first of your X inputs and number of bits. You follow that with the GREY command and now the accumulator hold the encoded position.

Note GREY code changes one bit per position

The problem you will have is frequency;

100 RPM = 1.667 RPS

1.67 RPS * 1024 PPR = 1.710 KHz data rate

1.67 RPS * 360 PPR = 601 Hz data rate

I think the best response you can expect from a standard input is less than 100 HZ but that depends on scan time too.

Created Date: February 08,2005

Created by: stimpsonjcat

You will likely not be happy using a standard DC input module to input an absolute encoder if you are trying to monitor position while moving. This would be no problem once the shaft stops of course, but while moving the DC input will not respond quickly enough to give accurate bit status to the PLC.

If you need shaft position, you could use a quadrature encoder to either the D2-CTRINT or H2-CTRIO to get position and use the Z pulse on the encoder to reset once per rotation. Of course, this count will not be retentive on power cycle, nor can this arrangement tell if the shaft moved while powered down.

Perhaps you could mix the two applications? Use the absolute to determine position on startup, then feed that value to the appropriate high speed card before starting your movement.