D0-06 Ramp and Soak in ladder logic

Hello all. I have an application where I am using the Direct Logic DL-06. I am trying to make a ramp and soak program in ladder logic to change the setpoint of the PID loop. The ramp and soak generator for this PLC cannot ramp slow enough......

Can anyone help me? I am using timers/counters to increment the set point by degrees/minute: After each tick of a counter, I:
LD K24
DIV K100 (I want to increment in units of .24degrees/minute)
ADD V3002 (V3002 is my SP register)
OUT V3002 (I want to add a constant value to my SP)

My timers/counters work as they should, however my SP will incrment in very weird numbers: ex. will increment by 32, then the next tick will increment by 78, ect.

can you post the ladder?

I'm rather surprised that it does anything at all. After the DIV K100 the accumulator should be holding zero since you aren't using floating point. And the setpoint is typically in binary anyway and you are using BCD instructions. Good luck with that.

Exactly what is the format of the setpoint? Degrees? Tenths of a degree? Hundredths of a degree?

BCE: Sorry: I cannot post the ladder, I can post the entire project if needed, or if you could tell me how to copy/paste the ladder....

Bernie: I have tried placing a BIN box underneath the "DIV", and this throws me off as well (I'm new to PLC's in general). Could proper BIN box placement help me out?
The format of the setpoint is currently whole degrees, but I'd like to do it in tenths... But the format is not important to me...

I just noticed an error in my original post, I am trying to increment by 0.024degrees/min....... not 0.24

If the format of the setpoint is in whole degrees then you can't adjust it in any finer increments. How about one degree every four minutes?

Use a standard timer (TMR) with a preset of K2400. Every time it times out add one to the preset:

LD V3002
ADDB K1
OUT V3002

Sorry, just noticed that you changed your increment. That means one degree every 40 minutes. Couple a 1 minute timer (TMR K600) to a counter with a preset of K40. Increment the counter every timeout of the timer. Add one to the preset every time the counter is done then reset the counter.

Is there a way to change the format of the set point to your knowledge?
What you mentioned will work for one segment of the profile, but I have other segments in which the slope is critical (we are heating and forming ceramics)...

The next slop needs to be incremented no faster than 1.44deg/minute over 5 hours. The closest whole number in degrees I can think of is 9deg/6.25min... However, this is too large a jump in the PV....

I appriciate your input...

(I might just need to use a temperature controller and simply re-transmit the set point, but this is undesirable)

The critical information is, what is the increment of feedback from the temperature measurement device (which I suspect is also 1 degree)? That sets the minimum step. You may have to start doing some research.

you could use a timer and counter combo then a = to to load any setpoint at any time then it would not even have to be liner thus you could run your whole heat treat process from start to finnishat whatever temps for whatever time. someone smarter might could tell you how to build an array to do this.a c-more micro could be added to change your preset temps for each different process or i belive you could use the lcd display thats sold as an option the06.the timmer counter thing works but i think the o6 also has built in yy/mm/dd/hh/mm/ss that could be used? give it some thought. there are many ways to get this done.

Hello

Not sure if this will help, but a few months ago I used A
DL-205 to communicate with several Delta Temperature Controllers over modbus, had to go this way due to noise. With Bernies help finished up project and works great. These controllers also have a ramp / soak function that can be set up. Through the communicaions you will have access to all set points etc...
They are also fairly in expensive.

Hope This Helps
Tom

The next slope needs to be incremented no faster than 1.44deg/minute over 5 hours. The closest whole number in degrees I can think of is 9deg/6.25min... However, this is too large a jump in the PV....

Click to expand...

No-no, you may be missing the point. You are not necessarily trying to come up with "the closest whole number". What you want is to use the smallest setpoint increment that all devices will accept. Usuallly that is 1 degree applied over some Time in seconds. Therefore, 1.44deg/minute = 60 seconds/minute / 1.44 degree/minute = 41.67 seconds for every 1 degree rise in the Setpoint. Set up a 42 second timer, and every 42 seconds, ADD 1 to your Setpoint. After each ADD, you also need to check to see if the Setpoint >= Desired Setpoint. If it does, then stop the ramp function (or replace it with the next leg of the ramp).

Remember, most of these temperature ramps are not exact, so if you use 42 seconds instead of 41.6666 seconds, I think you will be close enough for ceramic work. Your ramp will be slightly slower than the fastest allowed time - about 84 seconds slower in the 5-hour period). Otherwise, you will need equipment with more precision than PLC analog input modules.