Timer presets in rsLogix 500

[ofd23]

I am working on a project using a Allen Bradley ML1400 and would like to make it so the user can adjust a timer preset from the lcd. Does anyone know how I can set the preset of the timer to an integer(N) bit? Or any address that I could input a number into?

 

[TConnolly]

Many HMI units can address the timer .PRE word directly. However I recommend this only if the HMI supports range checking so that the operator cannot enter an out of range value. If the HMI doesn't support range checking then configure it to write to an N file word and then perform the range checking in your PLC. Then if the range is OK use a MOV instruction to move the N word to the timer .PRE word.

 

[Kidblue]

adjust a timer preset from the lcd.

Do you mean the LCD from the front of the ML1400?! Yes, I believe you can input variables directly to timers (or an integer address if you prefer, just use a MOV instruction to the .pre address).

Can check tomorrow in more detail with unit at office...

Regards,

Rob

 

[ofd23]

It doesn't allow me to enter N in the preset box of the timer though? And I am using the lcd display built on the plc not a hmi. There are pot max and min instructions i can use for setting a range as well. The only 3 letter I can enter are H, O, and U and as far as I know I don't want any of those!

 

[ofd23]

I think your onto something kidblu. So I just need to use the mov instruction and then move the N value to something like T4:4/pre?

 

[Ron Beaufort]

and then perform the range checking in your PLC.

if you're not sure what Alaric meant by this, I recommend that you ask about it ...

or ...

run a test by pretending you're an operator and you happen to enter a NEGATIVE number by mistake ... try that on a NON-production machine and see what happens ...

 

[ofd23]

I understand the plc errors if a negative number is entered, but can't i just set the pot min for 5 and pot max for 20 using the lcd function files?