Control Box on Wall Instead of Brewstand

I'm working on my plan for an automated system based around a BCS brain.

Originally, I was going to mount everything on the brew stand and just plug the brew stand into the wall when it was time to brew.

Conversely, I'm now thinking about mounting all of the electronic guts on the wall and then just plugging the brew stand into power cords coming from the box on the wall. I like the idea of it being on the way because I could then use it to also manage a fermentation chamber and cold box in another part of the house.

My biggest question is, how big of a pain/expense is it to splice thermocoupler probes, and is it a big problem to extend their wiring. Is this something that's commonly done?

I would not suggest splicing T/C wires if at all possible. Everytime you make a connection it creates a seperate cold junction and requires an offset calibration for this. RTD's on the othe hand can be spliced with negligable effects. Visit Omega.com. They have alot of temp probe connectors and extensions if needed along with some nifty panel jacks that will let you plug your probes in to the main panel. Just remember to match types as the temp curves vary from type to type.

Hmm... That's what I was afraid of.

Is there degradation when running RTD's long distances? For say like 20 feet over to where my cold box would be?

No problem at all. I have ran them in industrial enviroments well over 150 ft with no problem. RTD's are more forgiving but are not quite as precise usually. They are more than adequate for this purpose. When I mention precision I am talking about tenths or even hundreths of a degree.

One good thing about Rtds is that you can use shielded Beldin type of cabe to hook them up. You do not need expensive T/C wire.

You can extend thermocouples if you use the proper wire and connectors. I would be weary of running one 20 ft though. They produce an extremely small voltage so you need to make sure you aren't introducing any noise by using shielded wire.

Extending RTDs is a better route but you need to take a few things into consideration. PT100s only have 100 ohms of resistance at room temp. Extending a basic 2 wire PT100 can cause problems because the resistance of the wire can throw off your measurements. You can get around this problem by using a 3 or 4 wire RTD. These will compensate for the resistance of the wire when used with a device that has the proper circuitry for these types of RTDs

crane said:

You can extend thermocouples if you use the proper wire and connectors. I would be weary of running one 20 ft though. They produce an extremely small voltage so you need to make sure you aren't introducing any noise by using shielded wire.

Extending RTDs is a better route but you need to take a few things into consideration. PT100s only have 100 ohms of resistance at room temp. Extending a basic 2 wire PT100 can cause problems because the resistance of the wire can throw off your measurements. You can get around this problem by using a 3 or 4 wire RTD. These will compensate for the resistance of the wire when used with a device that has the proper circuitry for these types of RTDs

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I didnt know anybody still used 2 wire rtds. I know some places still have them in lab equipment but it is rare in most industrial instrumentation applications. It has probably been over twenty years since ive used them in the field. With a 3 or 4 wire rtds, length is not much of an issue because it uses a basic voltage divider circuit to compensate for voltage drop.

PT1000s are better than PT100s because the contribution of the lead wires is 10x less. Better still are thermistors, in the multiples of thousand Ohms, and even better than that are dedicated temperature measurement devices like DS18B20s which have a digital output. And best of all are sensors with radio frequency transmitters that don't use wires at all.

Ah I didn't catch that the OP is using a BCS for his controller. In that case I don't know why you are talking about extending thermocouples as the BCS only accepts thermistors. I prefer and thermistors myself. Their high resistance makes the resistance of the wire negligible and they are easy to interface with once you calculate the steinhart coefficients.

crane said:

Ah I didn't catch that the OP is using a BCS for his controller. In that case I don't know why you are talking about extending thermocouples as the BCS only accepts thermistors. I prefer and thermistors myself. Their high resistance makes the resistance of the wire negligible and they are easy to interface with once you calculate the steinhart coefficients.

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I didnt notice the BCS comment either. I was just speaking from experience with industrial controls and costs associated with them.

Ah I didn't catch that the OP is using a BCS for his controller. In that case I don't know why you are talking about extending thermocouples as the BCS only accepts thermistors. I prefer and thermistors myself. Their high resistance makes the resistance of the wire negligible and they are easy to interface with once you calculate the steinhart coefficients

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Well that's good to know. I really appreciate all of the information. I've started with a single PID and was planning to graduate to BCS in the near future. I hadn't realized that I'd need to switch out probes. Do you have strong preferences about your thermosisters? I see that Brewer's Hardware has a line of them... http://www.brewershardware.com/6-Temperature-Sensor-for-BCS-460.html

I have used thermistors from brewers hardware, Omega and some others I got from Digikey. I have had no problems with any of them once I got my analog front end working correctly to filter out power supply noise. All of them have been accurate within 0.1F in both an ice bath and boiling water so I have had no need calibrate an offset for any of them.

Didn't see this thread for a week, but better late than never.

I have a BCS mounted on the wall near my fermentation chamber. It controls the fermenter temperature directly. I use two CAT-5 cables to send all signals out to the brewery control cabinet. There is no problem having the CAT-5 connectors mounted on the box on the wall with the BCS nor on the brewery control. I'm using pre-made CAT-5 cables 16' long for the connection. When nothing is running in my garage the temperature probe for the freezer reads within .2 deg. of the ones in the brewery, showing me that there is no problem with the extra distance.

ChuckO said:

Didn't see this thread for a week, but better late than never.

I have a BCS mounted on the wall near my fermentation chamber. It controls the fermenter temperature directly. I use two CAT-5 cables to send all signals out to the brewery control cabinet. There is no problem having the CAT-5 connectors mounted on the box on the wall with the BCS nor on the brewery control. I'm using pre-made CAT-5 cables 16' long for the connection. When nothing is running in my garage the temperature probe for the freezer reads within .2 deg. of the ones in the brewery, showing me that there is no problem with the extra distance.

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ChuckO, do you have a wiring schematic you could share? I have almost all of the supplies for my system (BCS controlled Ferm 24/7 and brewery control on demand) and I want to start planning my control panel. Also, any pics of our set up would be really helpful.

chadillac7819 said:

ChuckO, do you have a wiring schematic you could share? I have almost all of the supplies for my system (BCS controlled Ferm 24/7 and brewery control on demand) and I want to start planning my control panel. Also, any pics of our set up would be really helpful.

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Here's a copy of the wiring schematic. At present I don't have any useable photos of the setup though.

I'm not happy with the program that created my wiring schematic, but I will try to explain anything that isn't clear.

View attachment brewery_and_fermenter_control.pdf