SLC 500 Rack module placement

[robh 12]

I am setting up an SLC 5/05 with a 13 slot rack. I will be using the following modules, 3- 1746-IA16, 1-1746-IB32, 3-1746-OA16, 1-1746-NI4, 1-1746-NT8 and in the future 1-MVI46-MNETC ProSoft Modbus module. I am trying to optimise placement. Is there a particular structure (or expert recommended) that I need to follow as to what order the modules should go? Should the ProSoft module be in slot 1? Or does it really matter? I know there has been issues with analog modules and their placement with the MicroLogix 1500. I checked around KB and couldn't find what I thought I needed. Thanks, Rob Edited 17 Feb 2010 by robh

[ElecPneuGuy 1]

None of that really matters. Typically, I'll see (and place modules) in an order where its the communication modules first, discrete inputs, discrete outputs, then analog inputs, then analog outputs. Yet, thinking to some GM projects that I've done, I've put the devicenet modules in the last slots of the rack. Its up to you. When you deal with Compact Logix stuff, the cards will rating of how far they can be from the power supply or processor. But, those are modular type racks, not an actual chassis. Have fun.

[Ken Roach 194]

In chassis-based I/O systems like 1746 (SLC), 1771 (PLC-2/3/5) and 1756 (ControlLogix) the order or sequence of I/O modules makes no difference in power consumption, scanning speed, or logical function. The Compact (1769 MicroLogix 1500 and CompactLogix), 1762 (MicroLogix 1100, 1200, 1400) and 1734 (POINT) I/O systems all require you to consider the power loading and the position of the modules. Compact is probably the most complex of these because of the use of "power supply distance rating" values. FLEX (1794) has aspects of both: it's a snap-together bus but much of the module operating power is not carried through the Flexbus so you just account for bulk power totals and don't worry about the position of the modules.

[Ken Roach 194]

As a matter of practice, I have the same habits as ElecPneuGuy; Comms closest to the controller, then discrete, then analog. Grouping the modules like that just makes it simpler to physically separate the different signal level wiring.

[jstolaruk 9]

I prefer the comm modules next to the CPU, then analog, low voltage inputs, any spare slots, and finally output modules.

[robh 12]

Great thanks for the replies. I have (will have, slot filler for now) com card in slot 1, dc input in slot 2, then ac inputs, ac outputs, tc input, then analog input.