Quick disconnect for custom temperature probes

I'm having a hard time designing the quick disconnects I want to use for my electric brewery. Actually, forget I said quick -- anything that acts as a disconnect without any threading will make me happy.

What I'm aiming for is exactly what Kal has done here: http://theelectricbrewery.com/temperature-probes

...except that I'm using a microcontroller and dallas 1-wire ds18b20 sensors so I can't use the spring lock assembly he's used (he states above the third image on that page, "Temperature probes as received," leading me to believe that whole assembly comes packaged with the RTD probe). If, however, I could find this spring lock assembly somewhere, I'd be more than happy to use it and figure out the thermowell myself.

The only solution I've come up with that I know will work is to use a tri clover thermowell, something like: http://www.brewershardware.com/1-1.5-Tri-Clover-Temperature-Probe-End-3.html

However, this is going in a 1/2" NTP tee (just like Kal does), so it needs to be a lot shorter. This is also crazy expensive... each sensor assembly would run me nearly $100 by the time I make the wiring, disconnect, etc. The flanges on the tri clovers are also really big; I think they'd look really awkward with all my 1/2" fittings.

I'd appreciate any good ideas... Here are my requirements:

- must accommodate ds18b20 sensor (1/4" - 3/8" ID thermowell)
- must be disconnectable without any threading
- must be very water resistant
- must fit 1/2" NTP
- coupling parts should not run more than $30 total, if possible

 

This might get you closer with minimal effort. Threaded disconnected though.
http://www.brewershardware.com/8-Temperature-Sensor-DS18B20-with-M8-Disconnect-Cable.html ($21.50)
http://www.brewershardware.com/CF1412.html ($13.00)
http://www.brewershardware.com/M8M3.html ($9.50)

 

I came across this (something I had seen before) which I think will do well: http://www.homebrewtalk.com/f51/how-pt100-rtd-1-2-npt-thermowell-225215/

I think I'll do the same thing, but with a few modifications:

since I'm using a bare ds18b20 probe, I'll attempt to do some epoxy potting to make it more resilient and waterproof. I'll probably also add a dab of arctic silver thermal compound at the tip of the probe to improve the response time.

I'll use a male XLR connector as it will be easier to clean / inspect. I'll jb-weld the connector in the thermowell to make the whole thing waterproof (Paul mentions that later on in the thread). At that point, the only potential for water to enter the thermowell would be through the front of the XLR connector.

Here are some of the parts I've found:

short thermowell @ ebay, $15 shipped: http://cgi.ebay.com/THERMOWELL-304s...0533079?pt=LH_DefaultDomain_0&hash=item2eaff4 8457
thermal epoxy + applicator gun, etc @ mcmaster-carr, $50: http://www.mcmaster.com/#electrical-component-epoxies/=kvm2g4
jb-weld @ amazon, $6: http://www.amazon.com/dp/B0006O1ICE/?tag=skimlinks_replacement-20
thermal compound @ amazon, $7: http://www.amazon.com/dp/B004Z9XG0I/?tag=skimlinks_replacement-20
male XLR plugs @ amazon, $1.50 each: http://www.amazon.com/dp/B000TH3ALK/?tag=skimlinks_replacement-20

I plan to make 6-10 of these, so that comes out pretty close to $30 each. I may skip the epoxy potting, as it's not only expensive but would be pretty difficult to apply between the XLR connector and the thermowell.

I'm already using male XLR connectors on the other end (my control panel) so this means I could use commodity female-female XLR cords ($6 each for 6ft @ monoprice) if I wanted. I've already got the parts to make the cables myself, so I'll probably go ahead and do that anyway.

Edit: it looks like XLR female-female are not very common. I still think having the male end at the brewing equipment will be easier to clean, so I'm not sure what I'll do about that.

 

Has anyone looked at using ethernet for a connection?

 

A lot of people have done that. I did it with my last 1-wire setup, but I was using two probes per cat5 run, which I think was a horrible idea. This time around I'm using telephone wire (4-conductor).

 

Why did you think this was a horrible idea?

 

It probably isn't, actually. I had a lot of failures reading from the temperature probes, but I was probably doing other things wrong.

 

Okay thanks, Still deciding how to run my temps back to a BCS... But def. thinking XLR on the kettle side.

 

Ebrewsupply is now carrying the xlr quick disconnects. Not affiliated with his site, just an enthusiastic customer. I wish he would stop adding stock options though. So tempting.

 

I plan trying 1/8" stereo plugs. Numerous options and it can't be any easier to connect and disconnect. Picked up a bunch of cables from Monoprice to test out.

 

The only disadvantage to these is that as you slide in the connector, you make connections between different pins. This can cause shorts that can be damaging. If you plug these in while your panel is unpowered, it won't be an issue.

 

I would go with the 1/2" NPT thermowells from Brewers Hardware or ebay and either (easy) 3 pin XLR connectors with mic cord, or (fancy) battery powered slave microcontrollers with LCD readouts and radio connections (e.g. NRF24L01+) to the master controller.

 

Auber now has their temperature probes in several digital formats:

http://www.auberins.com/index.php?main_page=product_info&cPath=20_39&products_id=322

 

very nice find! where was this 2 weeks ago >

 

I have since found out that Dallas recommends unshielded twisted pair (e.g. Cat5) rather than shielded cord (like mic patch cable) because of its lower capacitance. So I guess XLR is not the best choice after all. :|