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Home Brew Forums > Home Brewing Beer > Automated Brewing Forum > Any interest in starting new open source automated brewing project...for propane?

View Poll Results: Does this seem like a good idea?
Yes, this sounds awesome! 29 80.56%
No, this sounds idiotic! 4 11.11%
You'll shoot your eye out, kid!!! 3 8.33%
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Old 01-15-2013, 07:06 PM   #11
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Also, not trying to say bad idea or that my way is best. Just different way to get the same result. Good luck...subscribed.

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Old 01-15-2013, 07:28 PM   #12
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Quote:
Originally Posted by jrubins View Post
It seems like the control of a valve is more linear than an on/off switch.
Without the 'in-between' settings that an adjustable valve can offer, PID control is really only proportional and integral, but not derivative (or so I'm told by much smarter engineering types).
The way that Auber PIDs etc control heating elements is by sequentially turning them on and off using an SSR. There is no "in-between" setting on electric kettles, they are being turned on and off, on and off. The gradation of response is achieved by the duty cycle i.e. how long the on period is compared to the off period.

Graduated output can also be achieved by analogue means like twiddling a dial but you have to start worrying about whether turning the dial from 0 to 1 gives the same increase in power that you get by turning from 9 to 10, whether there is any backlash in your servo, and things like that.

Have you thought about what safety controls you will need?
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Old 01-15-2013, 09:18 PM   #13
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Quote:
Originally Posted by alien View Post
The way that Auber PIDs etc control heating elements is by sequentially turning them on and off using an SSR. There is no "in-between" setting on electric kettles, they are being turned on and off, on and off. The gradation of response is achieved by the duty cycle i.e. how long the on period is compared to the off period.

Graduated output can also be achieved by analogue means like twiddling a dial but you have to start worrying about whether turning the dial from 0 to 1 gives the same increase in power that you get by turning from 9 to 10, whether there is any backlash in your servo, and things like that.

Have you thought about what safety controls you will need?
No doubt, they are essentially doing a PWM control when a PID is used to control an off/on electrical system. However this isn't actually PID control, it's PI. The D (derivative) control comes with the ability to control gradations in the input (whether that's heat, electricity, or gas).
The control loop *definitely* requires tuning, not just for the gradations of the gas control, but the difference in liquid level (as there is less liquid, there is less energy input required to increase or maintain total temp).

Safety is tricky, the number one issue being that the propane doesn't continue flowing without fire. That's one reason that I liked the Brinkmann, because it would kill the gas flow if the fire went out. Unfortunately, that feature broke last brew day (after 6 uses, sigh). So, now that will have to be implemented in code.

Other issues are spark containment from the motors and controllers. I've seen others using ammo canisters, so that seems like a good sealable solution.


Any other safety issues that you can think of with an automated gas system?
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Old 01-15-2013, 09:37 PM   #14
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The derivative action in a PID controller has to do with the rate of change in either the process variable (temperature in this case) or error (process variable – setpoint). The derivative action will change the control variable (output) either up or down according to the magnitude of the rate of change. Therefore, you can still use derivative control while using PWM as it has nothing to do with the controllers output. Whether or not it is required is another question. Derivative control is often used to dampen oscillations and decrease overshoot.

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Old 01-16-2013, 03:49 AM   #15
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I have went the Mass flow controller direction with propane flow control for the high pressure flash boiler and boil kettle burners in the automated system. This lets the control system vary the fire as needed to control boiler temperatures, and step main boil kettle fire when boil is reached. The Mass flow controllers I used need multiple output power supplies, +15 -15Vdc and a 0-5Vdc control signal. As far as I know there is no analog output capabilities from the Atmel products in the 2 popular platforms being sold, so that would leave a PID controller with 0-5Vdc output as the only choice for most. One thing that I found is the need for a higher flow to light the burner successfully, then you can reduce flow to the minimum to keep burner running. Lowest maximum flow rate should be 30 SLM on N2, or less if calibrated with NH3 or other gas of similar density.
Here is a picture of what one looks like and one of the 2 setups I use https://picasaweb.google.com/kevin.l...01513186974322

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Old 01-16-2013, 03:51 AM   #16
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@jrubins If you want to implement PID on Arduino you should definitely check this out. A really good, easy introduction to what the PID terms mean and how they are calculated with code from a couple of Arduino libraries.

http://brettbeauregard.com/blog/2011...-introduction/

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Old 01-16-2013, 04:53 AM   #17
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Quote:
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I would just use a high-torque servo (boy would that make my life easier!), but the regulator is 4 turns lock-to-lock, and no servo I know of goes that far around, so I have to hack my own.
Take a look at this one:http://www.robotshop.com/ProductInfo.aspx?pc=RB-Hit-53
It has position control over 3.5 turns. It's not quite 4, but I bet you don't need it wide open.
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Old 01-16-2013, 05:12 AM   #18
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Quote:
Originally Posted by tob77
The derivative action in a PID controller has to do with the rate of change in either the process variable (temperature in this case) or error (process variable – setpoint). The derivative action will change the control variable (output) either up or down according to the magnitude of the rate of change. Therefore, you can still use derivative control while using PWM as it has nothing to do with the controllers output. Whether or not it is required is another question. Derivative control is often used to dampen oscillations and decrease overshoot.
Agreed. You have to take into consideration the response time of the system and period of the PWM output before you can declare that you can't achieve derivative control. Take for example an IPod, iPhone or pretty much any battery powered device with an audio output. The amplifier in these devices is a PWM (on/off) amp with a low pass filter. The response time of our ears is slower than the filtered PWM signal and therefore we perceive it as an analog signal. Similarly when you heat multiple gallons of water with a period of a few seconds or so the system naturally filters the PWM heat signal to produce an analog equivalent. On my electric boil kettle when I set the duty cycle to 50% I cannot see or hear any indication of when the element is on or off other than a light on my control panel because the water is absorbing the heat fast enough to filter it into its continuos analog equivalent.
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Old 01-16-2013, 06:01 PM   #19
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Quote:
Originally Posted by kladue View Post
I have went the Mass flow controller direction with propane flow control for the high pressure flash boiler and boil kettle burners in the automated system. This lets the control system vary the fire as needed to control boiler temperatures, and step main boil kettle fire when boil is reached. The Mass flow controllers I used need multiple output power supplies, +15 -15Vdc and a 0-5Vdc control signal. As far as I know there is no analog output capabilities from the Atmel products in the 2 popular platforms being sold, so that would leave a PID controller with 0-5Vdc output as the only choice for most. One thing that I found is the need for a higher flow to light the burner successfully, then you can reduce flow to the minimum to keep burner running. Lowest maximum flow rate should be 30 SLM on N2, or less if calibrated with NH3 or other gas of similar density.
Here is a picture of what one looks like and one of the 2 setups I use https://picasaweb.google.com/kevin.l...01513186974322
What's this mass flow controller thing? I've never heard of such a thing, but now I'm intrigued. What model/brand are you using? They seem to be quite expensive.
The analogwrite() function of an arduino can be used with a low pass controller to create an analog voltage for control of that type of system
http://provideyourown.com/2011/analo...wm-to-voltage/

BTW, your boiler is a work of art! Any documentation for your system someplace?

Quote:
Originally Posted by alien View Post
@jrubins If you want to implement PID on Arduino you should definitely check this out. A really good, easy introduction to what the PID terms mean and how they are calculated with code from a couple of Arduino libraries.

http://brettbeauregard.com/blog/2011...-introduction/
Cool, thanks!


Quote:
Originally Posted by tob77 View Post
Take a look at this one:http://www.robotshop.com/ProductInfo.aspx?pc=RB-Hit-53
It has position control over 3.5 turns. It's not quite 4, but I bet you don't need it wide open.
That is so full of win! I even found a cheapo version on ebay
http://www.ebay.com/itm/L-S785-Laser...item4d0732296d


Quote:
Originally Posted by crane View Post
Agreed. You have to take into consideration the response time of the system and period of the PWM output before you can declare that you can't achieve derivative control. Take for example an IPod, iPhone or pretty much any battery powered device with an audio output. The amplifier in these devices is a PWM (on/off) amp with a low pass filter. The response time of our ears is slower than the filtered PWM signal and therefore we perceive it as an analog signal. Similarly when you heat multiple gallons of water with a period of a few seconds or so the system naturally filters the PWM heat signal to produce an analog equivalent. On my electric boil kettle when I set the duty cycle to 50% I cannot see or hear any indication of when the element is on or off other than a light on my control panel because the water is absorbing the heat fast enough to filter it into its continuos analog equivalent.
So, I mentioned earlier that smarter folks than I made the statement about derivative control. In that case I'm referring to a conversation with friends who have actual engineering degrees, so I'm merely restating their input. I do, however, know a bit about audio, and understand the principle of a low-pass filter. I suppose what you are thinking is that a large mass of water, which takes some time to change temp will naturally act as a low pass filter due to the systems lag time. However, there is still quite a lot of noise with a PID controlled heating system using electricity to heat the water. I'm not sure if the relatively high volume:energy input would mitigate that.

Check out the temperature variation on this guy's coffee roaster project.
The red line is quite 'jagged' compared to the set point
http://www.instructables.com/file/FBH3PMTG1QWA5QW

More PID references
http://igor.chudov.com/manuals/Servo...hout-a-PhD.pdf
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Old 01-16-2013, 07:04 PM   #20
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The Mass flow controller is common to the chip manufacturing equipment, and is used for control of process gasses. The models I used are STEC SEC-4500 (20 SLM) and SEC-4550 (30 SLM) flow rates. They were purchased from Ebay for $30 and $75 about 6 years ago when I was purchasing the rest of the hardware for the automated system.
The automated system is built around a 1/4" tubing boiler that heats water to desired temps and creates steam for steam injection wort heating. boiler output is hard piped so no plumbing changes happen during operation, just water and gas flow adjustments to fit conditions.
The automated system combustion is vented and programmed for unatended operation if desired, overkill in the extreme, but intended as a scaled R&D system for larger scale systems.

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