carwash help please

[bwheat]

Here is another way to approach the problem.
Lets start the count as soon as the car enters the wash and makes the photoeye. The Car Length (CL) is the count when the photoeye breaks plus whatever offset you want to put in. The Leading Edge (LE) of the Car is the current count. The Trailing Edge (TE) of the car is the current count minus CL. You should know the position of each operation of the wash in counts. Like the foamer is 200 counts down the chain etc. Set up a limit test using the TE is the lower limit, the LE is the upper limit and the test is the position in counts of the operation you want to perform. When the limit test it true turn on your output. You could do some massaging of the LE and TE to offset when you turn things on and off.

Hope this helps, bit shifts make my head hurt.

 

[grayda]

looking in tha manual it states that limit testing is not offered on the A/B Slc 500 (1747-L511 5/01).

Can I do a "add" so that I can get the 60 pulses + L.O.V. (lenth of vehicle) some how?

 

[bwheat]

If the limit test function is not available in a 5/01 use the greater than and less than functions in parrallell branches. (how do you spell that word?)
After the trailing edge of the vehicle has broken the photoeye move the accumulated value of the counter to another register like N7:1. Be sure and use a oneshot because you dont want to continuously move the value to N7:1. I would put the offset number in N7:2. Then add N7:1 + N7:2 = N7:3. So N7:3 would be your L.O.V. plus the offset.

 

[grayda]

Going back to work will try.

Thank You

 

[bwheat]

If you have to use Greater thans and Less thans put them in series NOT parrallel for this application. Say the soad dispensor is 500 counts down the chain. Your L.O.V with offset is 200. Need to calculate the lower limit (when to turn off soap) which would be Soap_Pos + L.O.V. = 700. Your rung would look something like this. Current_Count > Soap_Pos AND Current_Count < (Soap_Pos + L.O.V).

I would setup some registers defining the location in counts of each device. Then do some math to figure out your upper and lower limits for each device once you have the L.O.V. Store each of these in a register to use in the >,< rungs to turn on the outputs.

Keep in mind there are LOTS of ways to skin this cat and sometimes you just have to pick the one that makes sense to you. When the panel door is closed and the machine works nobody can tell and most dont care what method you used.