Digital temperature probe thoughts

[bornholtz]

I want to build several digital temperature probes and don't want long wires permanently connected to the sides of the tanks.

I'm going to be connecting several temperature probes to a Raspberry Pi to monitor and log the temps.

Since the Dallas DS18B20 uses 3 pins I thought it would be good to have the probe connect to the pi with phone connectors (TRS).

What do people think about this approach? Will this work?


Here's a little more detail of what I had in mind:

Stainless Steel 1/2" NPT Thermowell - From about $13

Dallas DS18B20 - $1.49 each

female TRS connectors - about $1 each

1/4" Male TRS to 1/4" Male TRS - Varies depending on length needed.

On the Raspberry Pi side I can solder all of the connectors together.

 

[acidrain]

I used HAM radio microphone connectors. They are 4-pin, but they have screw-on retainers. Just use 3 or the four pins.
The problem I had with the phone jacks is that they are grounded to the frame.
https://www.google.com/search?hl=en...rice%2F4-pin-xlr-connector-price.html;640;480

 

[bornholtz]

I was worried about grounding too and thought about the 4 wire cables that are used with mic and stereo headsets.

I like these ham radio connectors because someone isn't going to accidentally plug the wrong thing to something that looks like a headphone jack.

The cables at monoprice are dirt cheap. Any recommendation for what to use for the actual cables? I suppose something heat resistant would be good but more expensive.

 

[alien]

My plan is to have little radio PCBs plugged into the DS18B20s with 3.5mm jacks.

 

[bornholtz]

My plan is to have little radio PCBs plugged into the DS18B20s with 3.5mm jacks.

Ooh! That sounds shiny and exciting! Can you elaborate a bit more on how you hope to do this?

And how many sensors do you want to be running simultaneously?

 

[alien]

So, I have designed a little PCB around a MSP430 micro controller which will plug onto a NRF24L01+ radio module. One board per DS18B20 plus one extra board as a "master" which gathers the information and forwards it to an Arduino running Brett Beauregard's PID library. The remote sensors use very little power - I am hoping to run them using Lithium coin cells. Each board will cost about $10 to make, the thermowell is about $10 more. I'm planning to make 3 or 4 initially. It's not my highest priority though so I don't expect to have it up and running before the summer.

 

[bornholtz]

Been doing more research and it looks like M-12 connectors may be the way to go.

Something like these:

https://www.oscsys.com/store/product/1001682

https://www.oscsys.com/store/connections/m12-1-wire

Not sure about the temperature limits of these cables though.

 

[CapnBry]

I use RJ-11 phone cord because they're easy and securely snap in and I have plenty of old phone cords around to cut a end off of. I'm told you can also splitters and daisy chain multiple sensors together but I haven't tried that.

 

[rockytoptim]

I use mini XLR connectors. Here is example. I didn't buy form this source just for info only.

Mini XLR Connector

 

[alien]

XLR's are very good for PT100s because the wires are shielded. Not really necessary for digital probes but nice all the same.