Raspberry Pi HLT/Boiler Controller

[Robbo100]

I have just finished making my Raspberry Pi Boiler Controller, and since my wife is bored with pretending she is impressed with it, I thought I would put it on the forum. Also, it might be useful for other people who want to make something similar.

I am using the device to control my DIY plastic Boiler/HLT, which is heated by two Tescos Extra Value Kettle elements (each powered from a different 13A plug). The device has made a massive difference to my brew-day, because it means I don’t have to keep monitoring the temperatures, starting stopwatches etc. It just sorts it all out for me!

The software is written in Python, which I coded onto the Pi remotely using WebIDE, which is an amazingly useful bit of software that allows you to connect to the Pi from another computer and program the Pi through your Chrome web browser.

The Python script runs automatically at boot, so there is no user intervention required, just power it on, wait 20 seconds for it to boot, and off you go!

Components Required:
- Raspberry Pi - £25
- SD Card - £4
- Slice of Pi/o V1.2 (used to easily interface digital i/o’s to the Pi) - £6
- Two push button switches - £2
- Wifi USB dongle - £5
- A dual 5V powered 240V 10A Relay board (for turning on the elements - £5
- Two “1 Wire” digital thermometers (you only need one, but I got carried away) - £3
- A 16x2 Liquid Crystal Display - £2
- A plastic project box - £6
- A small buzzer - £2
- Kettle plugs and sockets to connect the relay to the mains, and then onto the boiler - £10
- A couple of DIY bulkheads to get the thermometers in “contact" with the fluid (15 mm copper tank connectors) - £6
Total cost = 76 (Plus I had to buy a dremmel to cut holes in the project box, but that is more of an investment than a cost :) )

Functions:

- Welcome Screen at boot
- Two primary functions, HLT Mode and Boiler Mode
- HLT Mode:
- Display shows the target HLT temperature and current boiler temperature
- When target temperature is reached, the elements are switched off (and then one element is used intermittently to maintain temperature)
- Audio alarm is triggered when target temperature is reached
- Target temperature can be varied using Temperature UP and DOWN buttons (alarm function is reset if the target temperature is changed if the alarm has already gone off)
- Boiler Mode:
- System is commanded to Boiler Mode by pressing both temperature control buttons at the same time
- System turns both elements on
- When boil established (96 deg C), alarm is triggered (to prompt bitter hops) display then shows a countdown from 59:59 down to 00:00
- At 15:00 remaining, alarm is triggered again, for aroma hops prompt
- At 00:00 the alarm is sounded again and display prompts to go into cooling mode
- When Temperature Down button pressed, both elements turn off, and display shows the boiler temperature
- When 28 degrees is reached, the alarm is sounded again to alert the completion of the cooling cycle

Future Development Potential
- I would like to add a run-dry detection function to turn off the elements when the fluid levels go below a certain point (useful safety feature during the sparge)
- I will probably add a function to cycle one of the elements off during the boil to reduce the strength of the boil
- I might add a solenoid valve to open the cooling heat exchanger tap to fully automate the cooling cycle at the end of the boil phase
- I might make it post a message on Facebook when I complete my brew

I have just done a double brew-day using it for the first time in it’s completed state, and it rocks! :

Some photos below:

The innards:

In HLT Mode:

Connected to the boiler:

Boiler countdown:

Waiting for command to start cooling cycle:

 

[Robbo100]

P.S.

The same device could be used to control a fridge with internal heater for lagering with some tweaks to the software, so it is a versitile device! :party:

 

[dx4100]

Been thinking about doing something like this :) Good form

Would you be happy to share the code ?

 

[Robbo100]

Sure, I can supply links to all the items I bought too if that is useful.

Clearly you will need to use the same pinouts, or adapt the code if you don't.

 

[Robbo100]

I should add, that I had one problem with the device, in that the display does not seem particularly tolerant to high current devices powered by the same ring main being switched on, causing it to displays garbage. I got round this by adding some code that reinitialises the display when the temperature up button is pressed. It is not elegant, but it works.

 

[mattyhall22]

That's really impressive, it always amazes me how people's hobbies can come out with some brilliant inventions :thumb:

 

[Sone]

Very impressive, I've been meaning to find a good use for my pi now as it just gathers dust at present! Would love to try something like this :thumb:

 

[Fil]

cracking stuff,, lots of interest in all the details here..

 

[Robbo100]

I am struggling at the moment, because the forum makes my Mac crash when I write posts, hence the short reply!

I am happy to help, but for those who are interested in making something similar, you should start off by having a play with the Pi, with a Slice of Pi/o http://shop.ciseco.co.uk/k002-slice-of-pi-o/, and an electronics breadboard, with some LEDs with resistors.

I am happy to turn this into a tuition thread to help if needed.

Get this loaded on your SD card http://www.raspberrypi.org/archives/tag/webide, and play with writing some Python scripts to turn LEDs on etc.

 

[Robbo100]

I learnt BBC Basic 20 years ago at school and had never used Python until 2 weeks ago, so it is pretty simple to get going!

LCD dislpay is bought from here: http://www.ebay.co.uk/itm/HD44780-B...n-16x2-Arduino-Raspberry-Pi-AVR-/281211020326 and coded like this: http://www.raspberrypi-spy.co.uk/2012/07/16x2-lcd-module-control-using-python/

Thermometer bought from here: http://www.ebay.co.uk/itm/DS18B20-D...mponents_Supplies_ET&var=&hash=item41789ddcee and coded like this: http://www.raspberrypi-spy.co.uk/2013/03/raspberry-pi-1-wire-digital-thermometer-sensor/

 

[rpt]

I also have a Raspberry Pi gathering dust and might use it for something to do with brewing at some point. Have you thought of writing a how-to to put into the howto forum?

 

[Robbo100]

I would be tempted, but it wouldn't be a simple guide, would need circuit diagrams etc, so might take quite a long time.

 

[Sone]

+1 to a how-to :thumb: Will pick up a breadboard, few leds etc and have a play around!

 

[IOMMick]

Just wanted to give this a +1.

I new to homebrew and just finding my feet with kits at the minute, but I've already started reading up on my own brews - and given that I am a computer programmer by trade, with a Raspberry Pi lying about doing nothing, I'd say there is a fair chance of me revisiting this thread again as I get deeper into the hobby.

 

[Robbo100]

OK then chaps, you have convinced me.

Here is a wiring diagram.

I will put the information together and then create a dedicated "How-To".

Is this wiring diagram clear enough?

Robbo100

 

[tazuk]

love it :thumb: but is that a black dustbin is it food safe

 

[andyco]

Nice bit of kit :thumb:

Andy

 

[Robbo100]

love it :thumb: but is that a black dustbin is it food safe

Definitely is! PP5 food grade high temperature plastic.

http://www.amazon.co.uk/dp/B003MAFPZK/?tag=skimlinks_replacement-20

Not bad for £11.49 (although I got mine for £8 from my local pound shop!)

 

[tazuk]

8 squid from pound shop :electric:

love it :thumb: but is that a black dustbin is it food safe

Definitely is! PP5 food grade high temperature plastic.

Not bad for £11.49 (although I got mine for £8 from my local pound shop!)

 

[Robbo100]

8 squid from pound shop :electric:

I know! I would have had them under the trade description act if it wasn't such a bargin!