TM171 Retaintive Timer

[Josh1]

Hello,

I am quite new to Schneider ecosystem, I wanted to know how to use retaintive TON or TOFF timer in Ecostrucx HVAC.

Thanks in advance!!

[Bastian_Schmitz]

Hi Josh1,

Please explain what do you need exactly.

The integrated timer could not be specified as retain.

Did you need a timer which save his PT value also on power off?

Or did you need a timer which would not be reset if IN switches from TRUE to FALSE?

For the second case we would find a solution. For the first case unluckily not.

The retain attribut for GLOBAL VAR in ESME HVAC is not supported.

And did you use TM171O or TM171P or TM172 ?

[Josh1]

Thanks for the reply,

I'm using TM171O, and I want to use retentive timer, Which will start counting from where it left when power to the PLC is off.\

Thanks!

[Bastian_Schmitz]

Unfortunately this is not possible with TM171O.

What would you reache with this function. Maybe there is a other way to reach the same goal. 

If you deeper explain you goul we could find a different way.

[Josh1]

I want a timed process, I will give a certain time and then give start command when the process is completed start command is reset, If this process gets interrupted in between due to power failure or as such, after starting up again that process should resume from where it left before the interruption.

And also I am using one HMI to interface it with plc

Thanks.

[Bastian_Schmitz]

Hi Josh,

In that case I would see to possibilities which could be a soultion.

1. I suspect you use a "longer" time for your process (more hh:mm instead of  mm:ss). In that case you could use the internal clock of the TM171O. To calculate the time length calculate with the target var sysclock.* (*= hour,minute,secound....)

2. Which HMI do you use? If you use a SE Harmony or a Proface HMI which is based on the new HMIST6 base you could use retain variabeles on the HMI and transfer them via Modbus to the TM171O. The odler basic HMIs like HMISTO did not support retain variabels.

[Josh1]

Thanks, Bastian,

You are being really helpful, can you please elaborate me on how can I use that second method,

Thanks alot

[Bastian_Schmitz · Accepted solution]

If you could tell me which HMI do you use I could tell you how you could reach your goal. 

You could use in ESME HVAC the PULS FB to generate an impuls every 1s. Then you could count up a status variabel which you could link in the HMI to a retain variabel. In the HMI you need to generate a script you write this value at startup back to the PLC 

[Josh1]

Thanks Bastian you've been a great help!