No support from dealer

[mr_electrician 9]

I am trying to piece together a system to control a part checker where I work. My I/O count is pushing around 55. I need an incremental incoder to count at no more than 30RPM. I also have an old panelview900 touch screen I will be using. I was going to use a micro 1100 with four expansion cards but the I/O is starting to really get up the its limits!!!! I am getting no direction or help from the local distributer! I have been waiting for an encoder price for over a week!!! Where I work they really push the boundaries and limits of what a typical maintenance electrician would do. Don't get me wrong though, I have learned lots with respect to automation, programming, and design. (self taught that is!) I am having troubles though trying to finalize what would be best to use as far as a processor goes, as well as an encoder. We have RSLogix500(v7.30.10) and RSLogix5000(v16.03), and panelview32 programming software. I really need some advise from the seasoned automation engineers!!!!!

[PLCMentor.com 60]

You can help you I/O problem by moving up to the 1400. It has more I/O on the block and you are supposed to be able to add up to 7 expansion cards. You say your encoder is supposed to count no more than 30 RPM. What are you using it for? You need to figure out the resolution you want (ie, pulses per revolution). Your max speed of 30 RPM will then determine how the signal gets into the PLC (I am assuming you just need pulses). You may just need a prox switch for a pulsed input that can go to an input on the PLC. The micro has a high speed input on the block if you order the correct version.

[mr_electrician 9]

The 1400 has been considered. The only obstacle is I need to update my RSLogix500 in order to be able to program it. I may end up going that route anyways so I am not so tights on the I/O availability. The reason for the encoder is I was wanting accuracy when turning the part because I need to know when to start and stop counting holes that were punched in it. The resolution does not have to be super accurate. I think the micro can handle 20KHz? I would be no where near that at my low speed.

[Ken Roach 194]

"30 RPM" and "not super accurate" are only parts of the equation. You haven't described what turns the part (servomotor ? Hydraulic motor ? Turntable ? Donkeys ?) or whether you need to stop it in place or mark it or trigger an output. Let's say the part is circular and is 24 inches in diameter. Let's say you need to be able to determine the position of a point on the edge of the part with 1/10 inch precision. The circumference of the part is pi x D = 75.398 inches, so a point on the edge of the part is traveling at 75.398 * 30 / 60 = 37.699 inches per second. If we need 1/10 inch precision in measuring the position of a point on the edge, we need at least 753.98 counts, right ? Let's round up to a common encoder resolution of 1024 counts/rev. At 1/2 revolution per second, the encoder will be sending only 512 counts per second to an input, which means that the input should be true for 1/1024th of a second and false for 1/1024th of a second. "Seeing" an input for a little under a millisecond is outside what a normal PLC scan is going to do, so you're going to want to use one of the hardware counters on the MicroLogix controller (that's the 20 kHz counter you mentioned). Be sure you understand how the inputs are grouped and used for a high-speed counter function; typically inputs 0,1,2,3 are used for A/B/Z/Reset. Of course I've made a number of gross assumptions; these values won't match yours. The more information you post, the more advice you'll get !

[mr_electrician 9]

Ken, thank you for your reply. Bear with me as I am learning as I go. I will be rotaing the part via a 3 phase motor controlled by a frequency drive. The part is 7 1/2" in diameter. It has holes around the top, middle, and bottom of the part. I need to also sense the holes to verify that they are there and none were missed punched earlier. I am hoping to write some logic that will verify all holes are present and that it will start counting them regardless of if the hole is seen right away (allready infront of sensor). The part will not be loaded in the same position everytime, so the holes may or may not be seen right away. As for the encoder, it is more for just telling the plc that it has done a full 360. Edited 5 May 2010 by mr_electrician

[TimWilborne 108]

You don't really need an encoder for this. You just need a homing switch as a reference point. This way you can count holes from homing reference to homing reference. The Micrologix 1100 has 4 high speed inputs so this works out perfectly. It may be that you have chose the encoder for ease of mounting. If so, get an encoder with a Z marker and use it, leaving the A and B references unconnected

[mr_electrician 9]

I agree. I have decided to use a very small prox with a sensing distance of 0.8mm. Our talented millwright has made a mount for it so that it can sence/count the splines of the belt drive. Now I just have to wait for my Micro1400 and software upgrade to start programming it!! Should be a learning curve!

[TimWilborne 108]

Let us know how it works out for you!

[mr_electrician 9]

I have programmed my BSL (I think!) can someone tell me if this is going to work. I am trying to tell other periferal devices what is being inspected so they know what program to run when that part arrives. I am not sure as to what the R6 control bits do either. Also, is there any issues with creating excessive sub routines and internal bits. I like to do this to better track actions and break down different routines of the machine. Here is what I have so far. If I see a 1020 part at the inspection then I shift the bits. If I don't then I see a 1023. By doing what you see below cause a 0 to be inserted whenever there is a 1023 seen? You see my attemp in Ladder 13 rung 5 Edited 25 May 2010 by mr_electrician

[splicer480 0]

This sounds like a job for a Cognex vision system/part recognize.