Embedded Controls vs. PLC

[nornrich]

All,

Is there a rule of thumb for quantities being produced and when you migrate from a PLC platform and into an embedded controller?

Regards,

Rich....

Richard Nornhold, PE

http://www.ovenind.com

 

[itsmoked]

Not really. It is very hard to quantify. A strange shape may be needed that motivates an embedded design. Better durability, lower production costs, no regular code modifications, proprietary aspects, etc.

PLCs are generally grossly overpriced because the market they sell to is not generally very sensitive and the attitude of open future modifications invites an extensible general design. Often an embedded system can be much less expensive. I marvel that I could build an entire embedded control system to do a job for the price of just the "processor" module of the PLC being used to do the job instead.

If you have a specific application you care to describe my answer could be better focused to your case.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[nornrich]

itsmoked,

But your system cost doesn't include any design time costs. The writing of PLC code seems far easier then hammering out an embedded C program.

Regards,

Rich.....

Richard Nornhold, PE

http://www.ovenind.com

 

[ScottyUK]

If you're selling in to certain industries then you'll have a tough time pushing an embedded controller over a PLC however many you are selling. Heavy process, petrochem, powergen, etc like PLCs because they are familiar to the maintenance techs, the hardware is reliable and easily obtainable, programming and fault-finding are fairly well supported by the application software, plus the program is portable, or at least fairly portable, so even if a PLC OEM goes bust and the product is totally unsupported then the very worst case is to replace the hardware with a functional equivalent and regenerate the application from hard copy. Doing that with an embedded controller... no thanks!


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If we learn from our mistakes I'm getting a great education!

 

[jvjtech]

The writing of PLC code seems far easier than hammering out an embedded C program.

Agreed. As I noted in another post, I am a C programmer and have just ventured into PLCs. My C programming work is usualy in the area of embedded systems. The PLC program I developed over a couple 10s of hours, including the time taken to study the manuals and tutorials, took less time than what would berequired to develop a similar program in C. (Yes! I actually read the PLC manuals and studied tutorials.) ;-)
Add to that, no hardware design was required. On that note, I will briefly mention that a commerically available PLC will have defined and conditioned inputs and outputs, issues that would have to be addressed in the hardware design. For a one or two off project, if the PLC solution fits, it seems to this embedded developer the way to go. Regards.