Dear Friends ,

I have an old machine with three emerson servo motors each servo drive has simulated encoder ( 5 VDC , A , B , C ) that connected to old controller

i wanna to issue new program with CPU 1214 C DC/DC/DC , SB 1221 5 VDC to read encoders  , 4 Analog output to control drive speed

from the wiring of SB 1221 i noticed that all inputs must be connected to -ve voltage

is it meaning that i have to connect  ( invert A , invert B ) to SB 1221

i measured the voltage of A , B with 0 V by the multimeter , it gives me 3.3 voltage all the time ( with speed & zero speed ) what is the meaning of that ?

if i measure inverting A or inverting B , it will give me - ve ?

the first motor move linear ( pull paper) , the second motor move radial ( cut the paper )

so i have to control the cutting of the paper at specific length

no reverse movements so can i use only one phase of encoder ? this help me to read the three encoders

thank you

Hello.

The PLC does not need the negative phase. But now the problem -it might be that you have differential signals from your drive.

The 3.3V you measure - while it is pulsing or standing still? If moving: keep in mind you meter does not measure the peak voltage but the average.

Could you show an image on what signals you get from the drive? How was the connections used previously?

From your description the S7-1200 is not a good choice for the application. The S7-1200 is not a motion controller so the accuracy may not be what you expect.

Regards.

Hello ,

the connected signals are A & B signals only from each drive

the voltage between A & B = zero volt During Zero speed and any speed

the voltage between A and zero volt = 3.3

the voltage between B and Zero volt = 3.3

if i entered only channel A to channel of SB1221 is it work and count ?

 if i entered only channel A to channel of SB1221 is it work and count ?

Yes, it will work. The minimum voltage for an active state is 2.0V. Also AB pulse will work.

Please consult the System Manual for the PLC (A5E02486680-AJ). The specifications are there with wiring diagram.

Please note: CB needs 5Vdc power on L+ and signal ground on M. Do you have a power source from the servo drive?

bishoy naguib

Hello ,

the connected signals are A & B signals only from each drive

the voltage between A & B = zero volt During Zero speed and any speed

the voltage between A and zero volt = 3.3

the voltage between B and Zero volt = 3.3

if i entered only channel A to channel of SB1221 is it work and count ?

i have an external 5 V power supply so i will connect all 0 V connectors together

0 V from Drive with 0 V from  5 V power supply with 0 V of  24 V power supply

 Note: Sinking inputs only. That is: NPN. See attached.

Perhaps consider getting a converter from Phoenix Contact or Wago to get the signals to the voltage the PLC feels comfortable with. Then the voltage levels of different equipment is not going to be an issue for you. You'll be able to read the 3 encoder signals on the CPU in AB configuration. BUT up to 100kHz.

bishoy naguib

i have an external 5 V power supply so i will connect all 0 V connectors together

0 V from Drive with 0 V from  5 V power supply with 0 V of  24 V power supply

How critical is your positioning?

The start of a motion task may be delayed for up to 20ms.

do you mean that i have to use high speed DC converter to convert the signals from encoder to 24 volt and connect them in HSCs in main CPU 1214C

referring to the attached  wiring of SB 1221 can i connect 3.3 V to this module as an input or not ?i am not sure in this

The 3.3V is not the problem. There should not be a problem if the TRUE signal is 3.3V and the FALSE signal is less than 1V. Too little information to say what you have to work with. Best to test this.

The CB can handle x2 AB phase or x4 A phases or x1 AB phase and x2 A phase when you use an S7-1200 of firmware version 4.0 and higher.

Plan B is to get a converter and not use the CB.

bishoy naguib

do you mean that i have to use high speed DC converter to convert the signals from encoder to 24 volt and connect them in HSCs in main CPU 1214C

referring to the attached  wiring of SB 1221 can i connect 3.3 V to this module as an input or not ?i am not sure in this

bishoy naguib

if i entered only channel A to channel of SB1221 is it work and count ?

 Is your configuration of the HSC for two phase, A/B counter or A/B fourfold?