Siemens cpu314C-2PtP doing I2C

[chrsand]

Hello.

Can anyone please tell me, if my Siemens cpu314C-2PtP is able to communicate with socalled I2C ?

I have this 24Vdc motordrive, that I want to control from my cpu if possible. http://www.robot-electronics.co.uk/htm/md03tech.htm

I can control with analog output, but I'm wondering if it is possible using I2C ?

Hoping for a reply

 

[iant]

what does a 12C refer to

 

[RMA]

Since your 314C has 2 analogue outputs why not control your motor that way instead of trying to go the I2C route?

I'd also be interested to know what I2C is, never heard of it before.

 

[dcp325]

Hi,

The I2C bus you want to use is on a 5VDC level, so if you want to use that you should use a level converter between the MD03 and your PLC.

If I recall correctly the clock signal should be around 100kbit/s, (10us). I don't think your PLC will be that fast.

I would just keep it simple and use an analog out to control the MD03.

Kind Regards

 

[sthompson]

I2C is a Communications Protocol developed originally for Micro-Controllers.

http://en.wikipedia.org/wiki/I²C

Stu....

 

[chrsand]

Hi and thanks for answering.

Yes, maybe it would be best to use these analog outputs on my cpu314C-2PtP.

But I only have 2 outputs, so I gues I should buy a extra analog output module. Do You know if there is a limit for how many Analog Outputs I can add to my cpu ?

Been reading about how to use encoders in Simatic Step 7, but it all seems very complicated, at least to me.

I have these 2 wheelchairmotors, that i want to do some positioning with.

Would it be possible to mount some kind of optical sensors at the wheels, and use this feedback for accurate positioning ?

I also have some 24Vdc powerful linear LINAK actuators, that I want to control. Here I could also use the MD03 motordrives. I've been searching the internet for some kind of encoders that can follow these linear actuators, but I seem to find billions of information of rotary encoders, and have not found anything useful yet.

Are encoders the only choice, or could I maybe use potentiometers instead....... if so, do You have a link describing how to read from potentiometers with my cpu ?

Hoping for reply again.

Thanks

 

[chrsand]

........ and is it correct, that my cpu314C-2PtP only can read from ONE encoder ?

 

[DamianInRochester]

It seems like a microcontroller would be better suited to you goals.

 

[chrsand]

Hi DamianInRochester, and thank for answering.

I have some experience in Simatic step7 only using LADDER, so I actually don't know anythin about microcontrollers :-(

 

[dcp325]

Hi,

With the CPU314C-2PtP the maximum of I/O cards you can put in a rack is 8, so that makes a max of 66 analog outputs (including the two onboard) if you want ;-)

In the past I have done a project using 2 HTL-encoders (24VDC) with a CPU314C-2DP.
The encoders were used as counters (SFB47).
The CPU314C-2Ptp could handle up to 4 incremental 24VDC encoders for counting or measurements purposes, however it has only 1 integrated positioning channel available.
Positioning 4 axes could be done by comparing your counter value and adjusting the analog output accordingly.

An optical sensor on the wheels could be an option, but that depends on the speed and accuracy you want to achieve.

IIRC linak linear actuators are ballscrew types, so there definately is some rotating motion inside, maybe those are available with some form of feedback?

Reading from potentiometers is done using an analog input. The accuracy depends on how the resolution is of those analog inputs.

Kind Regards

 

[chrsand]

Hi dcp325, and thank You VERY much for Your help

Ok, so there should be enough analog outputs available using my cpu

The positioning, comparing counter values and adjusting the analog outputs accordingly, as You mentioned, is exactly what I was hoping for.

You also mentioned, that this cpu can handle 4 incremental 24VDC encoders for counting or measurements purposes...... I guess this is by using the 4 High Speed Counters in the cpu ? So it is not possible to get more than 4 High Speed Counters ?
What does incremental mean....... how many wirers are there ?

If I get 4 High Speed Counters, I could use 2 of them for the wheels, and the other 2 for 2 LINAK actuators.

I actually need several more motions, using actuators, but maybe I can use potentiometers for these. Can You please tell me more about reading from potentiometers ?

Again, thanks a lot

Best regards

Christian

 

[sthompson]

Something like this might be a better fit for this kind of project.

http://www.lpctools.com/lpc1768.lpcxpresso.aspx

Stu....