Does anyone know of a good isolated digital output module that's compatible with the USB-6000, USB-6001, USB-6002, and USB-6003 series cards?
I have been trying to install these in some industrial machinery designs, and they don't just play nicely with the 24V DC, 4-20mA, and 120V AC signals that are common in these scenarios. I have been using Grayhill, Phoenix Contact, and Crydom optoisolated digital IO modules (for example: http://www.grayhill.com/assets/1/7/IO-Intro.pdf) with the X-series cards with good results in these applications, but the X-series cards provide 5V I/O at 16 or 24 mA, with up to +/- 20V protection circuits. I can't find any isolators that work with the USB-6002's measly 4mA and 3.3V. Even the modules that say 3V only work with at least 10 mA, because they need to light an indicator LED AND the optoisolator! And when 10mA at 3.3V is provided, the output current is insufficient to drive many higher-current solenoids and so on.
I can use a logic-level FET like a FQP30N06L or a transistor array like a ULN2003A, but these are all PCB-level components and should have extra protection diodes and resistors, and need a PCB mount point (which could be the 779511-01 NI USB-6000 Series Prototyping Accessory, at a very reasonable $37), and they require the wiring team (who are used to using LOTS of screw and crimp terminals) to break out the soldering irons, which they don't like to do. Also, if they need replacement - because the electrically noisy systems present inside some of these machines WILL destroy an un-protected MOSFET - it's not going to be acceptable to ship one of those while it might be OK to ship something that can be installed with a screwdriver.
Has anyone found a digital isolation option that (1) mounts on DIN rail or a panel, (2) drives an amp or more at 24V with 3.3V at 4 mA input, and (3) is rugged enough to survive an industrial machine environment?