Dynamic scale point of analog values

Hi Everyone,

I am trying to create a program where I have an analog input value of 4-20mA and I want to be able to press buttons to set the min and max value of a scale of 200-1000.

For example, I have an analog value of 5mA, and by pressing I1 that value will be set as 200 on the scale. Then increasing the analog value to 18mA, and pressing I2 will set that value as 1000 on the scale. This will allow me to set the min and max values depending on when I press the buttons I1 and I2.

Have any of you worked on something like this before?

Thank you in advance.

ixo65

I'm sorry, but I didn't understand what you want.

 My apologies for the confusion.

A good example is setting the minimum and maximum temperature you want in a room. I would like to be able to calibrate the value where the fan will turn on and turn off. Let's say bring the temperature to 30 deg then press the max button to set 34 deg as the value where the fan will turn on, then lower the temp to 20 deg and press the min button to set 20 deg as the value to turn off the fan. Then if at any point you want to change those values just go to the temp you like then set it as min and max values.

hope this clarifies things.

ixo65

Is the analog input for setpoints the same as for the fan?

You must more explain. You know what you want. I not ...

 For this example, the analog value will come from a thermostat that I will connect to the LOGO analog input. If the thermostat range is from 18 deg to 40 deg Celsius. 18 deg is 4mA and 40deg is 20mA. If I want to turn on the fan with Q1 when the temp reaches 32 deg I will press button 1 (max) when the temp reaches 32 deg to set it as a max temp then when the temp reaches 24 deg I will press button 2 (min) to set that value as min temp to turn off the fan with Q2. So after setting those values the fan will automatically turn on and off based on the temp from the thermostat. In the event that I wanted to change the point where the fan turns on I just wait till the temp reaches that point then press the max button again to set it.

Does this make sense?

Something like this.

The van only can started if max temp > min temp.

Toeternietoe

Something like this.

The van only can started if max temp > min temp.

 Hi,

This works out really well.

Appreciate your help.

Thank you so much.

ixo65

 

Sonofjeffer77

 

ixo65

Is the analog input for setpoints the same as for the fan?

You must more explain. You know what you want. I not ...

 For this example, the analog value will come from a thermostat that I will connect to the LOGO analog input. If the thermostat range is from 18 deg to 40 deg Celsius. 18 deg is 4mA and 40deg is 20mA. If I want to turn on the fan with Q1 when the temp reaches 32 deg I will press button 1 (max) when the temp reaches 32 deg to set it as a max temp then when the temp reaches 24 deg I will press button 2 (min) to set that value as min temp to turn off the fan with Q2. So after setting those values the fan will automatically turn on and off based on the temp from the thermostat. In the event that I wanted to change the point where the fan turns on I just wait till the temp reaches that point then press the max button again to set it.

Does this make sense?

It doesn't make sense to me.

Why wait until temperatures are reached and then set threshold values? You can put the threshold values in the display and change them via the display.

I already understood after your last post that you want to save threshold values. I just didn't realize that it was the same analog input. 

 I apologize if I did not make sense. My example is not that great.