Monitoring Servo Pulses

[Rudi 0]

Firstly i would like to say thank you to crossbow who helped us on a F1/F2 PLC project with manuals, with this information we could succesfully upgrade to FX2N PLC's. We have the following problem where we would like to monitor the Differential output from a MR-J2SA Servo amplifier to a FX PLC High speed counter inputs X0 to X7. We need information on a practical circuit implementing the AM26LS32 / 32 Chips which converts the Differential output from the Amplifier to a Pulse input to the PLC we managed to get the chip working and can read the pulses on a scope but it isn't good enough to drive the input on the PLC. According to the PLC documentation the input current should be minimum 4.2 / 3.5mA which we obvouisly not achieving. Is there any commercially available Differtial input to Pulse output packages available ? The documentaion in the Mitsubishi manuals is not giving us all the information. Anybody that can help ? Thanks.

[panic mode 246]

to drive high speed inputs of the FX2N you need to make sure you get proper signal level and since inputs are tipicaly using optocouplers, there is minimum current you need to have to successfuly turn it on. we might be able to help more if you post your circuit

[Sergei Troizky 26]

What frequencies you will count? Servo steppulses may be too fast even for single high-speed counter, and you mention all high-speed inputs (by the way X6 and X7 are not high-speed counting inputs).

[Rudi 0]

Thanks for the reply Sergei and Panic Mode but we eventually sorted the problem with a Opto coupler the 4N25 we are also using a FX1N PLC and allthough i have mentioned inputs X0 to X7 we will only use X0 which can handle upto 10kHz the system is to track the actual positioning of a CNC machine Turret Drive in Jog mode The Pulse rate in the Amplifier is adjustable from 1 to 4000ppr to scale the output and we are only looking at one phase so that we do not exceed the specifications. Once we have completed our reliability tests i will post the actual circuit. Actually very simple. Using a Opto Coupler we ensure that the correct voltage levels get to the PLC. Our proto type circuit is now running for +/- 6 hours without any problems or errors.