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Old 10-19-2008, 01:47 AM   #1
Yuri_Rage
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As many of you know, I use an Arduino microcontroller to monitor and automate much of my brew process. I'm planning a major upgrade to my home brewery, including a complete rework of the microcontroller code and functionality. The project is largely on hold right now (mostly due to the crappy housing market), but I've been tinkering with a few bits and pieces lately.

I want a means of electronically measuring the fluid level in my mash tun and boil kettle, but a mechanical float-type level sensor will just get in the way (or get broken). Sure, a float switch would work, but it won't necessarily measure the fluid level without some manual intervention. So, I started looking at other sensor types and brainstorming. Here's the result:

My mash tun and boil kettle are about 20 inches tall, so if I run a thin tube down the side (vertically), and cap it, the pressure inside that tube will be 0 - 20 inches of water (or roughly .75 psi, max). Using a simple calibration scheme and conversion factor, that pressure can be measured and translated to kettle volume. The Freescale MPXV5010DP is a 0 - 10 kPa (0 - 1.45 psi) that operates on 5 VDC and generates a 0.2 - 4.7 VDC output signal that is proportional to pressure at a plastic port - perfect for measuring the pressure on a digital "sight glass."

Bench testing the 5010 sensor results in output that (with 10 bit ADC) is sensitive to within .1", which should be quite sufficient for the application. More to follow as I (very slowly) build the new system.

EDIT:
Turns out that my idea isn't exactly original. A bit of Googling turns up this paper by Freescale, detailing the use of a very similar sensor as a level sensor.
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Old 10-19-2008, 02:04 AM   #2
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I did a similar project back in school using PLC based control. It worked really really well. We had a couple different tanks and flow sensors to control input and output at various stage to keep a set water level (with their flow set by tank level). If I remember correctly it stayed within a few mm on the water level.
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Old 10-19-2008, 10:43 PM   #3
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Is heat going to be a problem with boil kettle mount?

 
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Old 10-20-2008, 01:33 AM   #4
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When I started reading, I thought you were going to measure the weight of the boil kettle to determine how much liquid was in the pot. Head pressure would be a good test as well.

Did you use your Arduino to measure pressure of your steam system?
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Old 10-20-2008, 02:16 AM   #5
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Heat won't be an issue - I'll use a stainless tube inside the kettle with a plastic or hard rubber coupler that runs to the sensor.

I use the Arduino to measure and control the steam rig.
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Old 10-20-2008, 02:19 AM   #6
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Yuri, you are a fricken gadget stud. I'm druck and not really adding to this thread, but just wanted to let you know how cool you are. And since you are a mod, I'm going to give you some respect. You ROCK, SIR!!!!
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Old 10-20-2008, 02:39 AM   #7
kladue
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I was curious as to location of sensor and exposure to combustion, and effects of heat on trapped air in sensing tube as water warmed and air expanded. The fun part comes with trying to work out a scaling factor that works with a rounded bottom tank.

 
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Old 10-20-2008, 03:56 AM   #8
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another nice aspect is it wouldn't be affected by the volume change of the water as it's heated (though it would be affected by the density)

 
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Old 10-20-2008, 04:04 AM   #9
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Quote:
Originally Posted by Shockerengr View Post
another nice aspect is it wouldn't be affected by the volume change of the water as it's heated (though it would be affected by the density)
But wouldn't it be affected by the expansion of the air in the chamber? I would assume that it has to be in a closed chamber so as the air heats the pressure will increase.
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Old 10-20-2008, 05:26 AM   #10
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Have a look at this guy's system Emile's Home-Brewing site: My Brewing Setup In particular the hardware section with a description of his MPX-based volume measurement. He seems to have have a working version of this and a whole lot more.

 
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