Do the pneumatic solenoid banks that have a separate 24 VDC power supply for the coils have to operate at 11-25 volts as well?
Answered by Bahman Radjabi, Pneumatic SIG Member, e-mail: bradjabi@smc-npdc.com .
A182) The 11-25 VDC requirement is only for the DeviceNet power. If a vendor chooses to use the network power to drive the solenoids, then of course, your solenoids (or the driving circuit for the solenoids) must support operation over the 11-25 VDC range. If the solenoids are driven from a separate power supply, it becomes your decision to specify the voltage and/or power requirements, but you don^t need to meet the same 11-25 VDC requirement that is specified for the DeviceNet power. In practice, a 24VDC DeviceNet power could potentially drop down to 11VDC when the network cable is about 500 meters long. This means that the power supply is connected to one end of the cable and the subject device is connected to the other end (500 meters away). The voltage drop is due to the resistance of the trunk cable that is a function of its length.
We are in the early stages of developing a DeviceNet network and would very much like to be able to add and remove nodes without powering down the entire network (hot-swap). Section 9-3.3 of vol. I states "Wires should not be installed while the network is active..." but it also states "...it is mandatory that devices can be removed without severing or disturbing the network." Can you elaborate on the possibility of hot-swapping?
Answered by Ray Romito, DeviceNet Trainer, e-mail: raromito@ra.rockwell.com .
A183) The statement from the spec "Wires should not be installed while the network is active..." pertains to wiring up the network cable to the connectors that have field installable terminations. Prior to errata 2, the Specification also noted a specific connection method that allowed for direct wire hookup to a terminal block, without the use of pluggable connectors. Being able to plug/unplug under power requires some type of pluggable connector. So if you support a pluggable connector, then you shall support being plugged and unplugged on a live network without disrupting the network. (Disrupt means to cause a fault or disturbance that requires nodes to be reset/power cycled to recover).