Hi friends,
There is a requirement to repair an old machine which is using 100s of I/Os with PLCs. These are very expensive to replace at the moment and my client has asked me to give a solution. I don't see that Microcontrollers can cater for this as there isn't any with such a lot of pins (at least according to my knowledge). I was told by one of my friends about FPGAs and was serching the net on that. I need an Expert advice on this. ;o)
Can anybody give me an idea for this please?
Also what's the best language to program the FPGAs? (I'll go with some tutorials).
Thanks & Regards,
Leo
Replacing PLCs with FPGAs?
Re: Replacing PLCs with FPGAs?
Hi Leo,
One of my friends has replaced a series of PLCs with a single FPGA in a corrugating machine in combination with an Atmel micro.
FPGAs are not hard anymore as there are lots of support applications and online help.
There are lots of cheap starter kits for both Xilinx and Altera FPGAs. (You could Google)
There are two languages in common called VHDL and Verilog which are used neck to neck in practical applications.
You could refer following docs as a quick start for programming.
For VHDL, http://www.ashenden.com.au/designers-gu ... -start.pdf
For Verilog, http://www.fpga.com.cn/hdl/training/ver ... 0guide.pdf
See my "Introduction to FPGAs" Topic for some more details.
One of my friends has replaced a series of PLCs with a single FPGA in a corrugating machine in combination with an Atmel micro.
FPGAs are not hard anymore as there are lots of support applications and online help.
There are lots of cheap starter kits for both Xilinx and Altera FPGAs. (You could Google)
There are two languages in common called VHDL and Verilog which are used neck to neck in practical applications.
You could refer following docs as a quick start for programming.
For VHDL, http://www.ashenden.com.au/designers-gu ... -start.pdf
For Verilog, http://www.fpga.com.cn/hdl/training/ver ... 0guide.pdf
See my "Introduction to FPGAs" Topic for some more details.
Re: Replacing PLCs with FPGAs?
Hi Leo ,
Your choice is very good. It is a very good idea to replace PLC' with FPGA's. Because you have benifits from both aspects .
i.e. in cost wise and also in accuracy wise. If we consider the cost , by using a single FPGA , you can replace more than ten PLC units.
( Normal PLC has 8 Inputs and 6 outputs). If we consider the accuracy , you can experience the real parallel operation with FPGA.
Because PLC's are virtual parallel and it's accuracy is depend on freaquency of the scan cycle.
But when using FPGA's for replace PLC's , you have to care about proper isolation of FPGA circuit from the outside world. Other wise
FPGA could damage. Optical Isolators are good and easy solution for this problem
Your choice is very good. It is a very good idea to replace PLC' with FPGA's. Because you have benifits from both aspects .
i.e. in cost wise and also in accuracy wise. If we consider the cost , by using a single FPGA , you can replace more than ten PLC units.
( Normal PLC has 8 Inputs and 6 outputs). If we consider the accuracy , you can experience the real parallel operation with FPGA.
Because PLC's are virtual parallel and it's accuracy is depend on freaquency of the scan cycle.
But when using FPGA's for replace PLC's , you have to care about proper isolation of FPGA circuit from the outside world. Other wise
FPGA could damage. Optical Isolators are good and easy solution for this problem
Re: Replacing PLCs with FPGAs?
I was told by that engineer who had replaced PLCs with an FPGA that the most important aspect of this is to achieve the same fail to safe requirements like that of a PLC. PLCs in general are fairly fail-to-safe circuits but not as critical as that of railway signaling circuits or nuclear power plants, etc... where near 100% fail-to-safety is achieved. This can be achieved by various means like supervisory circuits working on the main circuit or positive fail-to-safety achieved like in old relay systems.
When replacing a PLC with FPGA care should be taken to certify that acceptable fail-to-safety levels specially with regard to stop circuit in big machinery are implemented. This can usually be implemented by using the additional gating available in the FPGA to look after the main logic circuits. Peripheral circuit supervision available in FPGA can also be used in addition to this.
When replacing a PLC with FPGA care should be taken to certify that acceptable fail-to-safety levels specially with regard to stop circuit in big machinery are implemented. This can usually be implemented by using the additional gating available in the FPGA to look after the main logic circuits. Peripheral circuit supervision available in FPGA can also be used in addition to this.