Module Count · Chassis · Power Budget · Rack Layout
When to use: Use this tool at the FEED / detailed-design stage to convert an I/O list (DI/DO/AI/AO counts) into a module count, chassis/rack count, backplane power budget, and a recommended power supply. Apply 20–25% spare capacity per ISA / good engineering practice so the system can accommodate future additions without re-architecting. The rack layout table shows which slot holds each module per the selected platform's convention. Results are a preliminary estimate— confirm against the vendor's configuration software and module datasheets.
Platform & I/O Count
pts
pts
pts
pts
ISA: 20–25%
%
Module Density (pts / module)
Chassis Configuration
PSU is side-mounted; Slot 0 = CPU. PSU is side/end-mounted (no numbered slot).
Total I/O Modules
13
15 slots used · 2 racks (+1 expansion)
Per-Type Sizing (incl. 20% spare)
TypeReq. PtsModules
Digital Input (DI)584 × 16-pt
Digital Output (DO)393 × 16-pt
Analog Input (AI)203 × 8-pt
Analog Output (AO)103 × 4-pt
Power Supply (per chassis)
Backplane draw (raw)2860 mA
With 25% margin3575 mA (3.58 A)
Per-rack current1.79 A
Backplane power @ 5V17.9 W
Recommended PSU1756-PA75 / PB75 (5 A class)
Rack Layout
PSU is side-mounted; Slot 0 = CPU
Local / CPU Chassis · 10-slot
Slot 0
CPU/Processor
Slot 1
Comms/Network
Slot 2
Digital In (16-pt)
Slot 3
Digital In (16-pt)
Slot 4
Digital In (16-pt)
Slot 5
Digital In (16-pt)
Slot 6
Digital Out (16-pt)
Slot 7
Digital Out (16-pt)
Slot 8
Digital Out (16-pt)
Slot 9
Analog In (8-pt)
Expansion Chassis 1 · 10-slot
Slot 0
Analog In (8-pt)
Slot 1
Analog In (8-pt)
Slot 2
Analog Out (4-pt)
Slot 3
Analog Out (4-pt)
Slot 4
Analog Out (4-pt)
Slot 5
— empty —
Slot 6
— empty —
Slot 7
— empty —
Slot 8
— empty —
Slot 9
— empty —
Bill of Materials (summary)
Power supply — 1756-PA75 / PB75 (5 A class)2 ×
Processor / CPU1 ×
Comms / network module1 ×
Chassis / rack (10-slot)2 ×
Digital input module (16-pt)4 ×
Digital output module (16-pt)3 ×
Analog input module (8-pt)3 ×
Analog output module (4-pt)3 ×
Notes & References
Preliminary estimate only — vendor configuration software and module datasheets govern.
Backplane current per module (DI ~100, DO ~150, AI ~120, AO ~150, CPU ~700, Comms ~500 mA @ 5V) are representative; verify exact draw on datasheets.
Power budget applies a 25% margin to the summed backplane current.