Look for a software packaged called "Integrated Architecture Builder"
You can build a distributed I/O system in the software, choose your modules, and it will give you a material list. It will automatically tally your wiring terminal bases, bus power extenders, etc. If you're familiar with Allen-Bradley this is a very powerful tool.
If you're not, Point I/O has these basic components:
- Comm adapter: If you're using Ethernet you'll need a 1734-AENT for star topology or 1734-AENTR for device-level ring or linear topology (I prefer this method).
- Terminal Bases: You will need (usually) one per I/O card. The only exceptions are a few safety and specialty modules, so consult the documentation for each card. There are several choices here. It depends on if you want screw terminals or spring cage terminals. Typical part numbers are like 1734-TB for a standard eight-terminal screw-conection block.
- I/O Modules: A wide variety are available. They plug in to the terminal bases. Select based on your needs (For example: 1734-IB8 is a 24vdc 8-Channel Input card).
- Field Power Distributor (1734-FPD): You use these to "break up" the field power bus for your devices. Typically these are used for digital outputs and are tied into the safety circuit. So when your safety circuit drops out, the actual power to the outputs drop out without intervention in the program.
- Expansion Power Modules: These modules perform the function of an FPD as well as extend bus power to more modules. In a Point I/O system there are two power "rails", there is the 5vdc bus power that powers the modules themselves, and the field power (anywhere from low voltage DC to 240vac) which powers I/O devices. The 5vdc Point I/O bus power has a limit and can only support a certain number of modules. How many modules depends on which ones you're using (they all draw different currents). This is why I used Integrated Architecture Builder. It automatically puts an EP module in when I need it. But you can also review the documentation for each module as well as the limitations for the AENT/R and EPAC/24DC and determine this yourself. I often try to place an EP module where an FPD would go if I can since an EP also breaks the field power bus like an FPD.
- Address Reserve Module (1734-ARM): Use these to "reserve" a place in the rack for future expansion. Yes, you can add to the end but if you have a complicated rack with field power broken up you'll definitely want one of these. Especially in a situation where you have say a digital input you need to add. It'd be better to add it in with the rest of the inputs on the same field power bus than just slap it on at the end.
- Termination Modules (1734-CTM/1734-VTM): These modules don't take up an address in the rack, but instead are used as convenient landing points for field power. Use a VTM if you are wiring field input devices directly to the I/O cards and the Inputs are high-density (the lower density input and output cards have field power terminations on them already). The VTM is also convenient for three-wire analog devices (so you don't have to strip the cable way back for the one conductor to go to dc+). Use the CTM for outputs where you need to wire common (or neutral) field points. These cards are optional and are just offered as a convenience should you want it.
The Point I/O rack internally is a DeviceNet network, so you have a limitation of 64 modules including the comm modules. So the maximum I/O you could have on a single Point I/O rack is 63 cards, theoretically.