Sunday, January 25, 2009

PLC for the brewery

Well it is the off season for hops growing and the fields stand empty at present , even though planning has started for March.

I have been busy in the brewery at least and I was lucky enough to be a tester for a new PLC temp controller.

I firstly had to understand the concepts of State Machine programming and it did not take too long - surprisingly as I haven't done anything like this since Uni, almost 25 years ago.

OK, so the unit arrived early November from Embedded Control Concepts and I experimented with the system dry for a few days proving my programming ability. for more info.

The unit is packaged into a Black 6x4x1" Alu container

The I/O is all on one side - very neat for a beta box.

First out - the Ethernet port is self sensing , and even if directly connected does not require a cross over cable (I spent 30 minutes looking for the one I know I have and never found)
The system will auto fail to DHCP and self assign it's own IP address after 20 secs if directly connected.

I tried networking it through my wireless router and had no luck finding the assigned IP address, (I later found out the WIFI router has a table of all assigned addresses and I could have looked it up - DUH).

I had to force my Local Connection ethernet port to a fixed IP in the end, as the WIFI kept setting its IP config to same as WIFI. This issue we overcame during the beta. I will also attempt to look at connecting this to more than one PC to see how easy / difficult the first connection is. I later used a WIFI Print router to connect it remotely.

The external items needed and sold on the site are the Immersion temperature probe, 10K ohm NTC thermistor input. 6" (15 cm) or 4" (10cm) 304 SS stem and 1/4" NPT brass adapter with compression sleeve for adjustable insertion length. Accuracy of 0.2°C,
You will also need Solid State Relay's - rated for switching 15-40 amps, these are the ones that are switched with a 3-8v input
The system allows for 4 inputs and drives up to 6 outputs.

For my first test , I programmed a simple RIMS mash, and did a dry run, to confirm the parameters and switching of everything. A hot water test followed to confirm heating.

The gas control valve arrived in December , just need the pilot burner to be able to test that. I will use it with a temp probe to heat and keep to temperature the HLT water , both strike and later sparge water. This is still part of my testing regime for January.

So I have started programming for the day I can get the system to start on its own, firstly a delay till on, then gas valve will fire and HLT water will start to heat and keep its temp within 2 deg for strike water.
This means I can go to bed the night before after lighting the pilot light on the gas system and wake up with Strike water ready for me.
Next will be mash in (could do this automatically with a water valve), mash stirrer ON for 5 minutes, and then into mashing for 60 minutes and RIMS will take care of hitting and maintaining the mash temp. This program is what I have used for the last 4 brew days, which have all been very successful. The only issue I have had was an intermittent display problem where the timers stopped showing updates, they did keep working in the background and I discovered why the display had stopped.

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