Maximum Numbers of I/Os in Siemens S7-200 series

I'm to submit a proposal to a company currently using S7-200 with about +100I/Os. The company who'll be using my services will be supplying (adding) some equipment to this client`s existing equipment. Not much of a fancy work, Mostly holding Starters, a few lights, audible alarms, etc.

The reason to link all these equipment to one single controller is that;

1) Each equipment is started after an interval, for instance the 1st unit say "Conveyor" starts, and by the time product travels to the other end, the 2nd unit starts, and so on. (Currently they have a Single Panel in the centre and a Person activates them by monitoring them physically or some of the pieces have Timers installed). Adding more pieces of some equipment would only produce more hassle for this poor guy!

2) Only the person at the existing control station is aware of the status of the equipment. Consider this in case of and Overload Trip, Physical break-down of starters, loose wires, short circuit, etc. We intend to improve this at 1st stage to give them a HMI and different locations.

3) Once all the operation/Process/control and monitoring has been centralized, I propose to further enhance each of these by replacing the hard-wired Temp. Controllers to include in the PLC to be viewed (controlled) over HMI.

I want to know if it would be possible to increase the Number of I/O than the regular 7-8 modules, as supported by S7-200 CPU?

I know switching over to S7-300 would be good, but

i) Keeping old half of the system in S7-200 and Half designed on S7-300, and the handshaking involved inbetween kind'a makes me feel uncomfortable - as I've never done it before. Specially when its a Running Factory that does not tolerate shut-down!!

ii) or to replace the whole system to S7-300, which means to spend more to replace the S7-200.

I would like to have an expert opinion on this, considering the long run upgradation. (if we are abel to fetch the project)

let me know what you think.

Regards,

Hi Siemener.

I would try to switch completely to S7-300.
The problem with shutting down the factory can be minimized in this way:
Install a Profibus DP slave module in the S7-200 (6ES7277-0AA22-0XA0). Attach this to the S7-300 as a slave. Exchange the i/o in the S7-200 with the S7-300 in the program of the S7-200. You then have the possibility to seamlessly switch between the old S7-200 program and the new S7-300 program. This again gives you the opportunity to test the new S7-300 program "in-between" stops in the factory production. Then when you are confident you can switch to the new program for good.

In the long run, you can decide between keeping the S7-200 with the DP slave module, or exchange it with something else, like ET200M or ET200S.

For the PLC i recommend at least an S7 315-2PN/DP.
Sounds like a good project, and I am sure your customer will appreciate the difference between the old hardwired system and the new PLC+HMI controlled system.

Hi Siemener!

If you want to extend digital I/O more than 7 modules, a very easy way is using another CPU and creating a PPI net between the original CPU port and the new CPU port.

The net is very easy to configure using the netr/netw wizard in STEP7 - MicroWIN. In fact, it works like using Profibus-DP: you can configure digital inputs and outputs of the new CPU (slave) as an image of a V-memory area in the original CPU (master).

If you want more information and details about this solution, don't hesitate in asking me.

Regards,

Lorenzo Rivas
www.nubitek.com
S7-200 Wireless Solutions