Accurate Timed Output

I am currently working on a simple application with an MicroLogix 1500. There is a need to control a spray head (for silicone) that requires an accurate and repeatable timed output. We need to provide an accurate pulse width to trigger the spray head valve. The resolution has to be at least 5 milliseconds (at least that is what they tell me). Also, the request is that we would like to change the pulse width from an existing touch screen.

So basically I am trying to find an accurate timer that I could remotely control the time duration from the PLC.

I started going down the path of using one of the high speed outputs in PTO mode but I can't get anything longer than 1 second. I was hoping to find something that I can maybe control the timer duration with an analog output from the PLC and just trigger the timer from a regular output.

Any ideas or recommendations?

The scan time on your Micrologix 1500 is probably around 15mS, so I don't know if you can get the resolution that you are seeking. I have done similar applications in the past using a high-speed digital timer, such as the Omron H5CX, which has a resolution down to 1 mS. Then, use an output from the PLC to start the timer timing.

Just a thought. Good luck.
Best Regards

Use Selectable Timer Interrupt which may be set to 1ms resolution in ML1500.

Sergei Troizky said:

Use Selectable Timer Interrupt which may be set to 1ms resolution in ML1500.

Click to expand...

Thanks for the info. I did not realize that functionality was even there. I am going to test this right now.

abwiz,

Before you invest a lot of time in this, confirm your hardware restrictions, many output modules have 10ms response times.

Disclaimer: I have no mlx experence.

There are timing modules on the market that work within your specs. We use them interfaced to Profibus on our S7-Platforms in the high-speed filling processes.
I am sure that there is something that fits your criteria on the market that you provide an output to enable, send data via serial or ethernet, whatever you require.
I will look up the supplier for you.

Sergei Troizky said:

Use Selectable Timer Interrupt which may be set to 1ms resolution in ML1500.

Click to expand...

Couple that with an immediate output update instruction, IOM, and you'll be good to go. I recommend that you condition the logic on the IOM to call the instruction only when the output condition must be changed and not every time the STI routine runs as IOM adds considerable overhead.


Also, when scan times are long there is absolutely nothing to keep you from calling the same timer more than once in a scan and using the IOM in the main program.