Controlling Analog Output with NTC Sensor

2020-02-27T23:08:14.720000Z

he just had the simple numbers in his program, so unable to change, i do know the story about persistent, but this does not work when using 65535 for example.

Controlling Analog Output with NTC Sensor

2020-02-27T23:08:12.903000Z

RETAIN variables are stored in a reserved memory location, preserving values even after a power failure (start / stop / reset). PERSISTENT means, that the variables try to remain in the same location in case of a new software download as well... so after a download event a RETAIN PERSISTENT variable won't change value... (if possible).

Controlling Analog Output with NTC Sensor

2020-02-27T23:08:08.265000Z

yes correct, i would only hve the zero and the high 65535 also in a VAR, then you can change them online, or from any visualisation.

Controlling Analog Output with NTC Sensor

2020-02-27T23:08:06.560000Z

Originally created by: Supra^

Hello again!

Here's what i managed to get done this morning.

It definitely works just the way i wanted, and it was very easily accomplished with the oscat library

I will try to get the program done next week so i can test and tweak it. I'm also working on a visualisation that would allow to change the LCP1_low and LCP1_high variables AND that the variables would be remembered by the controller even after a reboot. The question is, which one should i use, RETAIN or PERSISTENT? And what's the difference between these two? Because in Finnish they translate to the same word and meaning

Controlling Analog Output with NTC Sensor

2020-02-27T23:08:01.883000Z

so use scale (or from w www.oscat.de w or make it yourself:

output=outputoffset+(outputspan)(input-inputoffset)/(inputspan)
this looks complex but is really simple.
outputoffset is 0V
outputspan= 10-0=10
inputoffset=25
inputspan=30-25=5
input= 23.4 example
now
output= 0+(10)(27.4-25)/5=4.8

this can be done several times so your input is real 274 as a word.
first convert this WORD_TO_REAL
divide by 10 to get correct temperature
then above scheme
then make output
oops wago server not working.
this is a little tricky as the i do not know the setting.
something like start is 2 and end is 32565 or close to this look in the datasheet.
you can do same again.
now with 32563 as outputspan for example.
then convert this back to a word with REAL_TO_WORD (use F2) and put this to your output
rtemp:=(WORD_TO_REAL(win1))/10;
(when you type above the program will ask for below)
win1 has address %IW0 type is word
rtemp is type real

conv1:=outputoffset1+(outputspan1)(rtemp-inputoffset1)/(inputspan1)
again it will ask now also give the constants in the definition.
conv2:=outputoffset2+(outputspan2)(conv1-inputoffset2)/(inputspan2)

out1 address is %QW0 type is WORD;
out1:=conv2;

if this is too difficult, just give all numbers and i will write you a simple demo.
but probably you understand above.

Controlling Analog Output with NTC Sensor

2020-02-27T23:08:00.205000Z

Originally created by: Supra^

Thanks shooter for the fast answer. The real problem for me is to get everything started because i've got no experience in how to make a variable analog output signal. At the time i cannot supply any good flowchart, but the principle is as follows:

Components
Wago 750-881 Controller
Wago 750-464 AI (NTC10k specific)
Wago 750-562 AO 0-10V
Wago 750-600 End module

Motor valve with control signal input 0-10V (0-100%)
NTC10k temperature probe

So, i measure temperature from the NTC sensor, and when it reaches a specific setpoint (too high temperature) it will start to open the valve, i.e. the voltage will be >0V.

I thought of testing this first with the HYSTERESIS FB, but it only gives BOOL as output. As i would like to test this also, the question is, how to tell that the BOOL value should be 0V when FALSE, and 10V when TRUE?

The final version should be able to open the motor valve in steps, depending on the temperature (as described in my first post), e.g:

25.0c = 0V
25.5c = 1V
26.0c = 2V
26.5c = 3V
27.0c = 4V
27.5c = 5V
28.0c = 6V
28.5c = 7V
29.0c = 8V
29.5c = 9V
30.0c = 10V

A PID-based control is not considered at the moment, because i have no way to be sure the PID control will turn off when the temperature is back to OK again.

Controlling Analog Output with NTC Sensor

2020-02-27T23:07:55.413000Z

yes very good possible.
and very simple to make, you can go even better by pid control or (with fuzzy)
just make a flow sheet and i will send you a program as a begin.

Controlling Analog Output with NTC Sensor

2020-02-27T23:07:53.781000Z

Originally created by: Supra^

Hello again!

Currently i'm working on a solution for controlling motor valves through temperature. I immediately thought about the Wago 750-881 controller, which i have been using for many other projects. I assume it is possible to control the output value (0-10V) to activate for example from 25-30c? e.g. 25c=0V, 26c=2V, 27=4V.....30=10V. However, i didn't find any functions to do this direct.

I have already placed an order on the parts for the system, and cards for the Wago controller (4xAO 0-10V, 4xAI NTC), just want to be sure it can be done with the wago, and hopefully relatively simple? Any tips on which functions to use is also appreciated, i usually work with Function Blocks.

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