The way we have it at work is just with diodes. Basically what they have done is two power supplies, fed from different UPS', with their positive connected to a bridge rectifier (graetz bridge) AC input. Both power supplies are connected to a different AC input. (If 3 PSUs are required, a 3 phase bridge can be used). The load is connected to the positive pin of the rectifier. During commissioning a load is connected (normally just the complete IO cabinet) and one PSU is switched off. Then the output voltage is regulated on the running PSU such that the voltage at the IO cabinet modules itself, is 24.0V. Then the other PSU is switched on, and the first PSU switched off, repeating the process. Once both are done, both are switched on and left on. The "power good" contact is wired in series with the primary MCB aux. contact, so failures can be detected easily.
The negative connections of the PSUs are wired in parallel to a common rail....
If a PSU dies, there is 0 voltage interruption. If the output voltages are 100% the same (which can easily be achieved by putting a voltmeter between the positive outputs of both PSUs and then voltage regulated to 0.00V) the PSUs will do proper power sharing too. If the voltages are not 100% the same, the one with the highest voltage will be the "primary" PSU. That is also the way to "force" a primary power supply.
All in all a total cost of a few dollars for a 25A (or greater) bridge rectifier, which can be mounted on the panel for cooling...
I have an installation with 2 softstarters that use rs485 modbus and an ethernet gateway that is the master of that ring
I can send and receive all data needed using Modscan32 over TCP connection on laptop to both softstarters
so far i havent been able to get a response from the softstarter when using the PLC - error code 5 and 4.
SO I guess the question is, does the slave ID get sent along with the 'message' when using modbus ip function blocks, so the gateway knows where to forward the message?
It was a wiring issue as Simon suggested. It appears everything is working now. I am registering counts on a change of state. I also was able to get the HSC to Freq function to work, so I have frequency in 0.01Hz increments to convert to RPM. I don't have the motor available at the moment to test it on that, but I counted the number of times I manually activated the switch over 1 min. and the rpm reading was reasonably close. I'm sure that improves with more time and consistent pulses.
Thanks everyone for the assistance. Now I just need temperature and air volume control on a hot air blower, to set up some cycles to open an close a solenoid for a spray nozzle, and a counter and I will be in business.