Siemens Logo! 12/24RCE as a frequency converter

Hallo.

I want to count pulses from a flow meter (HRI-Mei B6) Each puls are 6ms and one pulse are 10L and convert the pulse to a >20ms longer pulse .

My project is that the pulses from the flow meter are to controll a dosage pump via the fast inputs

(i3-i8) on the  siemens LOGO! 

The pump only allows a minumum contact duration for >20ms so the pulse (I think) from the flow meter are to short.

So I wondering if some one can help me with a program, I have treid but my programing skills are limited so I´m stuck.

I also wondering If there are sombody that can tell me how to conect the pulse meter to the LOGO!

Best regards

/Mikael

If I have understood correctly, the frequency is not converted, but only the pulse duration is extended. See the LOGO program and connection diagram in the appendix for a possible solution.

The program only can work correctly, if the time between 2 pulses is greater than 20ms.

Version 1 needs additionally a cylce time greater than 6ms, but this is in most cases no problem.

Version 2 buffers the pulse and generates a pulse as long as you want.

Regards, Scorp

Thank you for helping me.

I have read about my pulse meter and it use the NAMUR standard (What is a NAMUR Sensor? - intrinsically safe sensor - RealPars) and the signal seems to be a analog signal that use a small current flow insted of  switching cirquit that I first thought.

So I have to rethink about this project.   

Any ideas how to work this thing out?

The bottom example the picture shows a connection for a digital plc input. Maybe the resistor 1kOhm must be adapted for the Logo input. I have never worked with Namur sensors.

Do you have an order number of your sensor or a link for further details ?

Hallo

I have scan the documentatiom that was included to the flow meter.

Thank you

Sorry, but i cannot see any details for a sensor with mode B6 in your documentation. Perhaps the mode of your sensor is settable ? You can do following things:

1. Try out the shown circuit with the 1kOhm resistor at a Logo input

2. Use a signal conditioner with Namur input and digital outputs, search in internet

3. Try to change the mode of the sensor, if possible

4. Find more details for your specific sensor

5. Use another sensor with pnp output to connect directly to plc inputs

In case of a signal conditioner it might be possible to find something with integrated pulse extension. Then you don't need a Logo plc for this step.

Regards, Scorp