Idec micro 1 using encoder as up/down counter

[b.nelson]

The max rpm I will be running the traverse is 15rpm. so that equalls 1.5 pulses per second. I think the micro 1 can handle that. The traverse moves the table not the spindle. The lead screw moves .200" per revolution...devided by 6 pulses per revolution give me .0333" per pulse. This plc is used only for the slowing and speeding of the traverse. (to save time) the table will speed up until it gets close to the cut then slow down to feed speed before cutting. If you still think this wont work please let me know.

- Brandy

 

[hesham]

it will not work

Hi all
First PLC
After reviewing the manual which mike provide a link for i found that 1-the micro 1 scan time equal 8 micro/instruction which is a very big time for length measuring applications.

2-As Mike said only counter 45&46 are up/down counters(reversable)as mentioned in manual.counter 45 can't be used because it needs to inputs one for counting up and one for counting down which is not the case for encoder.

3-counter 46 can be used because it have a direction input and one counting input.In this case brandy will use only one channel from the encoder(Note that in this case he does't need encoder any more).

4-counter 46 is not a high speed counter so the plc will not treat it as interupt as all the plc's i know did(theis plc have not interupt function).this will effect the accuracy because the counter will depend on the scan time.
HSC commands executed and not depenant on scan time.

5- Micro 1 have a ctach input(input 0) for pulses with .5 msec duration.i think that this will not help because as brandy said he have 1.5 pulse/sec so no need for the catch input.

Second Encoder
After reviewing the encoder which Brany select from Bourns and ttthe encoder Specifications I found a surprise
1-It seems that this encoder outputs is throug mechanical contacts with Bounce 5 msec .it needs as recomended by the manufacture to a debouncing circuit (5 msec) to eliminate this effect.This will cause a severe inaccurate measurment.
after this i can conculde to Brandy that even resoultion is not a big issue in your system as you said(I don't know how) and you need .03" resoultion.you will never get it.
Waiting for comments
BR

 

[elevmike]

Your PLC may be able to handle this but I'm concerned about the encoder. Insustrial encoders can better deal with the enviroment, vibration, shock, cutting oil dirt, electrical noise etc..

Therotically it can be done, but there are pit-falls, and reliability, and setup for different jobs may become a problem. If you would be willing to spend a few extra bucks you will get much better results.

Now to answer you question:

CNT 45 is a duel Pulse up/down counter that can be used with the encoder to track position in either direction. Max cout = 9999

FUN 100-146, or FUN 200-246 can be used a presets to create limits, or set the position at which you want to change speed, and or stop reverse etc. There are a limited number of presets available, and you will need to use a programmer to change them if necessary.

So the answer is: based on the low pulse rate "technically" yes you can do this if you choose to.

Sit down and draw a line on a paper, and mark the line with the event points, (1 start, 2 slow, 3 fast, 4 stop, 5 reverse etc) and encoder values at each point. Use this graph to create a flow chart, than make the code. Draw a graphical picture of your process before you do anything else.

Good Luck,

Mike.

P.S. hesham, posted while I was writing this, He brings up another good point regarding the encoder. Dont get so cheap that you risk serious damage to your equipment, or waste hours of time going nowhere. Buy a real encoder here .

 

[hesham]

More investigations

Hi again
After doing some more investigations to that Encoder i found that
1-this Encoder can fit with Integrated circuits(IC's) .I think that the PLC will never sense it.It's output compatiable with TTL loads(5 volts signal level)Plc can't detect it.
It's not for industrial applications (Please see the running torque)
and how this will be coupled to the lead screw?
Brandy
Go with mike adivce and invest more money in an industrial incremental encoder and a new plc .this my advise also.
Good luck