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Home Brew Forums > Home Brewing Beer > Automated Brewing Forum > Help me decide: Arduino or Raspberry Pi for brewing and smoking applications
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Old 04-03-2013, 03:29 PM   #1
jfenton78
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Default Help me decide: Arduino or Raspberry Pi for brewing and smoking applications

Greetings all,

I'm interested in building a "controller" for my brewing and fermentation, but would also like to use it for smoking. I don't need anything too fancy such as web monitoring or controlling 30 valves. I basically would use it to monitor 3-5 temps and control 3-5 relays/SSRs. What are you recommendations for the microcontroller? I'm currently looking at a Arduino or Raspberry Pi. Should I look at anything else?

I've already got a brewtroller that I'm using, but I'd like to have a second "more standard" system to play with and that I can code. I don't have a strong coding background, but I learn quickly.

Let me know your thoughts on Raspberry Pi or Arduino and why. THanks

Jeff

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Old 04-03-2013, 05:34 PM   #2
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All depends on what type of coding you want to do and the user interface you want. I'm playing with a Pi right now and can see where I can come up with a sharp looking web based user interface that's not possible with the Arduino. But I can see where code written for the Arduino could run much faster than a Pi hosted web project.

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Old 04-03-2013, 07:48 PM   #3
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Thanks for the feedback. I would like to keep the coding to a more minimal form if that makes sense. As for the interface I'm okay with just text. After more reading it seems like people are using the Pi for the UI or as a network interface, but still require the Arduino for the inputs and switching. To me it seems like the Arduino is what I need, but am I missing out on something with the Pi?

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Old 04-03-2013, 08:32 PM   #4
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Quote:
Originally Posted by jfenton78 View Post
Thanks for the feedback. I would like to keep the coding to a more minimal form if that makes sense. As for the interface I'm okay with just text. After more reading it seems like people are using the Pi for the UI or as a network interface, but still require the Arduino for the inputs and switching. To me it seems like the Arduino is what I need, but am I missing out on something with the Pi?
No, I think that are just leveraging hardware they are familiar with and they are adding the Pi as a user interface driver. But I've look at enough of the mixed designs and researched enough hardware to convince myself that it can all be done in a Pi. I just wish I could find a USB controlled stir plate!
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Old 04-03-2013, 08:48 PM   #5
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Does anyone feel constrained by the memory of the Arduino Uno? I would like to program it to measure temp, switch a couple of relays based on temp, and sound alarms. I'll likely use just on/off and PID based switching.

I'm not looking to recreate the brewtroller, but maybe just simplify it with the core functionality that I'd like to play with.

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Old 04-04-2013, 07:47 PM   #6
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I built Arduino based controllers for my brew system (Uno for hlt, rims, and kettle pid control with data logging) and fermentation controller (old Mega simple on/off controller and data logging). I did not hit memory issues with either. Honestly, I might not be using but half the memory in either application.

One thing to consider, the Arduino is a micro controller and runs in real time. The timing in your code will be consistent. There are not operating system processes to delay the next command.

While the Raspberry Pi typically runs Linux based OS and sometimes the processor has to run operating system processes and delay processing the next command in your code. We are talking about a handful of clock cycles at 700MHz, but some people consider that an issue. I did just read that there are now real time operating system builds for the Pi, but I've never used one. I use my Pi to store and serve data like you mentioned in your post

Maybe a computer engineer or computer scientist will chime in. I don't want to regurgitate what I read incorrectly.

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Old 04-04-2013, 08:05 PM   #7
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Quote:
Originally Posted by kwadric View Post
Maybe a computer engineer or computer scientist will chime in. I don't want to regurgitate what I read incorrectly.
Hi!

I highly doubt you'll run into programming memory space issues on the 'Duino with a project like this (unless you want ethernet)

Arduino:
Pro - Real-time operation, many analog-to-digital pins with reasonable accuracy (8-bit, I think?), extensive documentation (good for someone new to this area!)
Cons - Limited UI options (think push buttons/LEDs/small LCD/seven-segment displays), limited internet connectivity (RAM/PROG space limitations). Also the ethernet shield isn't cheap. Stuck with C/Wiring for language (might not be a con depending on your experience)

RPi:
Pro - Internet is easy (including WiFi!), full linux on the board means full TCPIP tools, GUI, video out, etc. Cheap (actually cheaper than Arduino + Ethernet shield!). Many choices of programming languages (yay, Python!)
Con - No Analog-to-Digital (but you can add cheaply with these http://www.digikey.com/product-detai...%2FP-ND/319422, a breakout board like this http://www.adafruit.com/products/914 and some soldering), linux experience def needed to leverage full power. NOT guaranteed real-time execution (though it might not matter too much in this case).

I'd say weighing the above: Go arduino if you DON'T want internet connectivity and can live with the GUI limitations. If you want to control/administer/view the thing over the web, go RPi, just keep in mind you will need an external A2D converter circuit.

ETA:
To expand on the real-time issues: These really only come into play if you're looking to switch something off and on with millisecond accuracy (say to keep an LED at half-brightness, or other PWM tasks)- that would be difficult to do with the RPi out of the box. If on the other hand you only want to turn a fridge on/off every few minutes to keep a constant temperature (for exampe), you'll have no problems with the RPi. Feel free to PM me with any questions along the way, I've got a few years experience in this area.
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Old 04-05-2013, 02:04 AM   #8
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I think that mhespenh summed it up very well. His point about the RPI for pulse width modulation to turn something on and off quickly, like pulsing a solid state relay for a hot water heating element, is very good. Without the real time operating system, the control loop might not be stable enough because the pulse width might vary. I'm sure if you dig around the forum you might find some RPI electric brew system that work directly from the GPIO. I'd think it is possible, I just don't know how stable the temps would be.

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Old 04-05-2013, 03:13 AM   #9
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Quote:
Originally Posted by kwadric View Post
I think that mhespenh summed it up very well. His point about the RPI for pulse width modulation to turn something on and off quickly, like pulsing a solid state relay for a hot water heating element, is very good. Without the real time operating system, the control loop might not be stable enough because the pulse width might vary. I'm sure if you dig around the forum you might find some RPI electric brew system that work directly from the GPIO. I'd think it is possible, I just don't know how stable the temps would be.
The reality is your mash temperature is going to change slowly, giving the Pi plenty of time to react. The real challenge is programming a PID algorithm into either machine because without a PID algorithm you are far better off using one of the PID controllers from China to manage your mash temperature.
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Old 04-05-2013, 05:23 AM   #10
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Quote:
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The reality is your mash temperature is going to change slowly, giving the Pi plenty of time to react. The real challenge is programming a PID algorithm into either machine because without a PID algorithm you are far better off using one of the PID controllers from China to manage your mash temperature.
Exactly right.

For something like that you don't need real-time accuracy (like PWM), just a good, solid PID algorithm, which the RPi would be more than capable of handling. The question then is your logic and programming skillz. Either way, RPi or Arduino, you still have to climb that mountain.

PID controller design is a fun/horrible project that every aspiring hardware/software co-designer should take on at least once.
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