Food-safe waterproof digital temp sensors (DS18B20)

[The-Engineer-That-Brews]

I'm a big fan of the little digital temperature sensors based on the DS18B20 chip: cheap, accurate and fully waterproof.
Be careful though... I was singing their praises to @chopps the other day and he pointed out the cables aren't food-safe.
He's right: the cables are PVC so definitely not good to be dangling in your mash tun.
Fortunately if you shop around you can get ones with silicone cables - e.g. DS18B20 Waterproof Digital Probe Temperature Sensor Silicone Cable Thermometer | eBay

Note that these are NOT the type of sensor you can plug into an Inkbird / STC-1000 etc

 

[The-Engineer-That-Brews]

Unfortunately despite their ‘waterproof’ description these started malfunctioning after a few times immersed in near-boiling water. Unfortunately a firm pull on the cables reveals the sensors are ‘dry’ inside the cans instead of being potted in epoxy resin. So even though the cases are crimped down onto the cable in three places the water gets in there eventually. I have dried them out and injected some epoxy resin in, hopefully that will waterproof the connections…

 

[Agentgonzo]

Unfortunately despite their ‘waterproof’ description these started malfunctioning after a few times immersed in near-boiling water. Unfortunately a firm pull on the cables reveals the sensors are ‘dry’ inside the cans instead of being potted in epoxy resin. So even though the cases are crimped down onto the cable in three places the water gets in there eventually. I have dried them out and injected some epoxy resin in, hopefully that will waterproof the connections…

I've found out that quite a few things can be waterproof at 20°c, but not at 100°C for an hour. A lot of glues/sealants etc will soften/melt I expect.

 

[Vinylwasp]

Unfortunately despite their ‘waterproof’ description these started malfunctioning after a few times immersed in near-boiling water. Unfortunately a firm pull on the cables reveals the sensors are ‘dry’ inside the cans instead of being potted in epoxy resin. So even though the cases are crimped down onto the cable in three places the water gets in there eventually. I have dried them out and injected some epoxy resin in, hopefully that will waterproof the connections…

I have a couple of solutions for you.

1: 100% waterproof, food safe, silicon covered, epoxy filled DS18B20 probes from BrewPi (not cheap but excellent quality)
2: 60cm Stainless Thermowell tube - just sit in your beer and slide any DS18B20 probe into it without worry

HTH.

 

[The-Engineer-That-Brews]

I have a couple of solutions for you.

1: 100% waterproof, food safe, silicon covered, epoxy filled DS18B20 probes from BrewPi (not cheap but excellent quality)
2: 60cm Stainless Thermowell tube - just sit in your beer and slide any DS18B20 probe into it without worry

HTH.

Thanks
1. Sounds interesting: will have a look
2. Unfortunately can’t use a thermowell as my mash tun is a bucket-in-bucket design with a double skinned wall :-)
Have just given my ones (now epoxy filled) a for about 1h30 cycling between 95° and 30° and they seem to be OK

 

[The-Engineer-That-Brews]

I've found out that quite a few things can be waterproof at 20°c, but not at 100°C for an hour. A lot of glues/sealants etc will soften/melt I expect.

I think the problem is often that if there’s an air space then on each thermal cycle the gas pressure builds up on heating, and then on cooling a bit of water gets sucked in… after a few cycles the water builds up

 

[The-Engineer-That-Brews]

I have a couple of solutions for you.

1: 100% waterproof, food safe, silicon covered, epoxy filled DS18B20 probes from BrewPi (not cheap but excellent quality)
2: 60cm Stainless Thermowell tube - just sit in your beer and slide any DS18B20 probe into it without worry

HTH.

Yes those sensors look just the job - will probably get a few of those. Ironic they are from a Pi store, as I’ve just spent the last few days writing a hardware (pio) 1-Wire driver for the RPi Pico

 

[Vinylwasp]

Yes those sensors look just the job - will probably get a few of those. Ironic they are from a Pi store, as I’ve just spent the last few days writing a hardware (pio) 1-Wire driver for the RPi Pico

I'm running the older Spark 3 from BrewPi with the rpi web interface, which controls my HERMS and Ferm temps via 1-Wire (scroll down to see the build). If you're aiming to do any temp control with those probes aand your rpi driver you might want to have a look at the SSR Expansion boards, at 12euro they're an absolute bargain. You can control 2 SSRs with each board.

 

[The-Engineer-That-Brews]

Heh - @Vinylwasp my HERMS/ferm controllers are all ESP32 based with web interfaces using AJAX/CORS

The RPi Pico driver was just to contribute to the repo

 

[dtashmore]

this is my first reply to a post in this forum, I may be able to add an alternative, I use this sensor in a number of my home made projects, my method is to buy the sensor from a local electronics parts distributor and solder some thin 3 core Mylar cable to it insulated with 1mm heat shrink sleeve, I then use 6mm soft drawn copper pipe I obtain from a local refrigeration company I seal one end, I use copper flow solder but that requires a good hot flame so the other alternative is plumbers lead free solder, the pipe can be cut to any length so the other end his never submerged, I use a slow setting liquid epoxy and push it down the tube with the sensor/cable assembly then seat the sensor with a length of stiff wire, the top and can be formed into a hook as it is soft drawn which is another advantage. I hope this is helpful.

 

[Vinylwasp]

Heh - @Vinylwasp my HERMS/ferm controllers are all ESP32 based with web interfaces using AJAX/CORS
View attachment 82138
The RPi Pico driver was just to contribute to the repo

That looks pretty slick, and see you're using a PID to hit your target setpoint too. Nice work. Those ESP32 boards are pretty cheap too. Ever thought about packaging it up and marketing it?

 

[grooves]

I used an ESP32 to build my own replacement for a Braumeister controller when the original went on the blink. It works great and has more functionality than the original - latest feature is Alexa integration so I don't even have to look at the controller screen to understand whereabouts in the mash/boil the brew is currently.

 

[The-Engineer-That-Brews]

this is my first reply to a post in this forum, I may be able to add an alternative, I use this sensor in a number of my home made projects, my method is to buy the sensor from a local electronics parts distributor and solder some thin 3 core Mylar cable to it insulated with 1mm heat shrink sleeve, I then use 6mm soft drawn copper pipe I obtain from a local refrigeration company I seal one end, I use copper flow solder but that requires a good hot flame so the other alternative is plumbers lead free solder, the pipe can be cut to any length so the other end his never submerged, I use a slow setting liquid epoxy and push it down the tube with the sensor/cable assembly then seat the sensor with a length of stiff wire, the top and can be formed into a hook as it is soft drawn which is another advantage. I hope this is helpful.

Thanks for taking the time to reply, and for sharing your innovative solution. Great to hear from you!
For people who might consider using that approach with a stainless steel kettle, it may be worth covering the copper tube with silicone tubing to prevent it touching the stainless steel in the presence of acidic wort

 

[The-Engineer-That-Brews]

I used an ESP32 to build my own replacement for a Braumeister controller when the original went on the blink. It works great and has more functionality than the original - latest feature is Alexa integration so I don't even have to look at the controller screen to understand whereabouts in the mash/boil the brew is currently.

That looks like a great bit of work! I never considered Alexa integration (although I’m an iPhone user and I think Siri is a bit trickier to do). I‘m fully in favour of hands free / voice control during the brewing process though: sticky, hot liquids and touch screens don’t coexist well. On my brew days the neighbours probably wonder why I’m calling “hey Siri, remind me to put the first hops in in 45mins” etc.

 

[The-Engineer-That-Brews]

That looks pretty slick, and see you're using a PID to hit your target setpoint too. Nice work. Those ESP32 boards are pretty cheap too. Ever thought about packaging it up and marketing it?

Thanks!
I did consider it but getting proper electrical safety certification, CE marking etc. would be quite hard work, and I don’t think it’s a particularly big market :-)
In general I tend to just Open Source stuff that I think people might find useful, and a couple of the bits and bobs on the official RPi Pico repository are down to me.
I’ve done a couple of custom builds for micro-breweries though: that’s quite good fun.

 

[gingerneil]

Zelijko, the dev of the nautilis ispindel relay (and some other cool stuff) has developed an ESP32 based solution for controlling heating and cooling via SSR. This is the current version, but he is in the middle of expanding the features and capabilities and I expect will release the next version soon.
https://www.nautilis.eu/portfolio-item/nautilis-wifi-temperature-controller-v6/

 

[foxy]

this is my first reply to a post in this forum, I may be able to add an alternative, I use this sensor in a number of my home made projects, my method is to buy the sensor from a local electronics parts distributor and solder some thin 3 core Mylar cable to it insulated with 1mm heat shrink sleeve, I then use 6mm soft drawn copper pipe I obtain from a local refrigeration company I seal one end, I use copper flow solder but that requires a good hot flame so the other alternative is plumbers lead free solder, the pipe can be cut to any length so the other end his never submerged, I use a slow setting liquid epoxy and push it down the tube with the sensor/cable assembly then seat the sensor with a length of stiff wire, the top and can be formed into a hook as it is soft drawn which is another advantage. I hope this is helpful.

There is good reason why copper isn’t used on the cold side of brewing, copper is toxic not only to yeast but to humans also. Any copper stripped on the hot side of brewing can be used by the yeast as nutrient, over a certain level it becomes toxic to the yeast. Better off using silicone tube with a push on silicone tube enclosure.

 

[dtashmore]

There is good reason why copper isn’t used on the cold side of brewing, copper is toxic not only to yeast but to humans also. Any copper stripped on the hot side of brewing can be used by the yeast as nutrient, over a certain level it becomes toxic to the yeast. Better off using silicone tube with a push on silicone tube enclosure.

good point, I have never used it during ferment just for temperature stabilisation during the 1 hour of contact during mashing, the original post just mentioned the mashing process.

 

[Vinylwasp]

Thanks!
I did consider it but getting proper electrical safety certification, CE marking etc. would be quite hard work, and I don’t think it’s a particularly big market :-)
In general I tend to just Open Source stuff that I think people might find useful, and a couple of the bits and bobs on the official RPi Pico repository are down to me.
I’ve done a couple of custom builds for micro-breweries though: that’s quite good fun.

Building microbreweries sounds very appealing.

Have you had a look at the Spark 4 as an ESP32 based platform? It's pretty slick, fully modular, allows a huge amount of customization and compared to a lot of systems I've seen, is very affordable.

I'm running the slightly older Spark 3, but uses the same firmware. UI is Docker based. I'm running it on Rpi3. It''s also OS

 

[The-Engineer-That-Brews]

Have you had a look at the Spark 4 as an ESP32 based platform? It's pretty slick, fully modular, allows a huge amount of customization and compared to a lot of systems I've seen, is very affordable.

Not really... I'm sure it's very good, but I prefer to design and build all my own hardware and software :-)