pulsing the start switch

[wglespaul]

Im running a few simple ladder programs in Simatic Step7. How do I pulse an input on and off so i can see its effect on the output. And also how can I get the LEDs of the modules of the live PLC to light?

Thanks

 

[Terry Woods]

"How do I pulse an input on and off so i can see its effect on the output."

Connect a real push button to the input.
Refer to the manuals for proper wiring techniques.


"And also how can I get the LEDs of the modules of the live PLC to light?"

The Input LED's will light up when you connect and use Input devices.

The Output LED's will light up when the code tells them to.

 

[PLucas]

Wglespaul,

There is one important line in Terry's reply

Refer to the manuals for proper wiring techniques

You do need to have the L and M terminals on the digital input and output cards (assuming that you are using 24v cards not 110v AC ones) connected to your 24v supply, otherwise your LED's will fail to light.

Paul

 

[dchartier]

Hello, Paul;
one way to pulse a bit in Step 7 is to use what Siemens calls a clock bit.
Open Hardware Config, double-click the CPU to open the CPU properties window; open the cycle/clock memory tab, and click on the Clock memory checkbox. Then write in a byte number (10, for example) in the clock byte dialog box. This sets up MB10 as a clock byte, where each bit pulses at a different frequency (specific frequencies are described in the help for the tab).
Now in your ladder simply add one of those bits (M10.3 for example) in series with any output you want to control: a simple example to flash an output (change the clock bit for different frequencies)

M10.3 Q0.0
--------| |-----------------------------( )

You can modify this easily to check your inputs (this example will block the flashing of the output depending on the state of the input):

M10.3 I4.0 Q0.0
---------| |------| |-----------------( )

Hope this helps,
Daniel Chartier