Digital sight glass

[phillc]

Here is an article that may be a good starting point:
Spiff's Electronics Notebook: Arduino and Freescale MPX Pressure sensors

 

[sjlammer]

Hey Yuri,

For those of us who are a little less controller savy, do you know of any resources to learn the basics of digital controllers. Make magazine has inspired me to use controllers in some of my many projects (both beer and non beer). I just don't know where to start. PS I'm a water supply engineer, so i can handle technical manuals.

 

[bull8042]

This is what I am using for my level sensing - Devantech SRF02 Sensor

Just scale the distance read to actual volume of the keggle. It is a linear scale and the sensor is up out of the way of everything, eliminating the cleaning issues.

 

[thevalkrye]

be aware that using head pressure to measure liquid level is also dependent on the specific gravity of the liquid...so as your boil progresses your S.G. increases and your sensor will actually "think" there is more liquid above it than there is..you will have to do the math on it...i don't know if the inaccuracy will be enough to worry about..but there will be one.

p=(hxS.G.)/2.31

p = pressure in psi.

h = height in feet

S.G.= specific gravity of the fluid

2.31 = a conversion factor. (2.31 feet of fresh water equals 1 psi.)

 

[LooyvilleLarry]

Thanks for that bit of info thevalkrye. I just ordered a couple of these to experiment with.

 

[phillc]

be aware that using head pressure to measure liquid level is also dependent on the specific gravity of the liquid...so as your boil progresses your S.G. increases and your sensor will actually "think" there is more liquid above it than there is..you will have to do the math on it...i don't know if the inaccuracy will be enough to worry about..but there will be one.

p=(hxS.G.)/2.31

p = pressure in psi.

h = height in feet

S.G.= specific gravity of the fluid

2.31 = a conversion factor. (2.31 feet of fresh water equals 1 psi.)

As has already been pointed out, you will also have to compensate for the expansion/contraction of the measured volume as it heats and cools. In my boil kettle, I observe a little over half a gallon difference on my pyrex sight glass from mash temp to boiling.

 

[LooyvilleLarry]

I'd bet you can use a constant ( say 1.040 SG) and get PDC... (Pretty darn close) .
For 2' of beer, there is about .04 diff every 10 SG points.

P H SG
4.62 2 1
4.6662 2 1.01
4.7124 2 1.02
4.7586 2 1.03
4.8048 2 1.04
4.851 2 1.05
4.8972 2 1.06
4.9434 2 1.07

 

[thevalkrye]

As has already been pointed out, you will also have to compensate for the expansion/contraction of the measured volume as it heats and cools. In my boil kettle, I observe a little over half a gallon difference on my pyrex sight glass from mash temp to boiling.

that is true too....as you heat the liquid there is a slight increase in volume so there is a decrease in density with temperature...but the bigger area of concern would be that as the density increases because of water evaporating...the liquid you are measuring will actually be getting heavier per unit volume (the specific gravity)..because you are concentrating it more.

when we take specific gravity reading as home brewers most of our hydrometers are calibrated to a certain temperature (20 deg C i think) to standardize it.

the difference you see in the sight glass is due to thermal expansion and isn't really related to the specific gravity of the fluid.

ya you should be able to get PDC using a constant..you just might have to play around a bit to get the most accurate constant...and as long as you are aware of the error you can tailor it to suit your needs...good luck with the experiments!!

 

[phillc]

This is what I am using for my level sensing - Devantech SRF02 Sensor

Just scale the distance read to actual volume of the keggle. It is a linear scale and the sensor is up out of the way of everything, eliminating the cleaning issues.

That sounds like a decent solution, but pretty expensive... How well do the sensors hold up to heat and moisture? Mounting one in a hot water vessel seems like it would wreck it in short order. My HLT is covered to conserve heat, so it would have to be mounted inside with a significant amount of steam...

 

[Brewers Hardware]

Hey Yuri,

For those of us who are a little less controller savy, do you know of any resources to learn the basics of digital controllers. Make magazine has inspired me to use controllers in some of my many projects (both beer and non beer). I just don't know where to start. PS I'm a water supply engineer, so i can handle technical manuals.

goto Arduino - HomePage

There is a huge amount of information there. There is what they call the Playground which has lots of code examples. There is a forum and there are also lots of other resources. I'm also working on an Arduino format to control and monitor my brewery. I'd always wanted to learn to code but always got too bored after "Hello World" and so this is a great platform for me to learn on since I can use the practical application for my brewery. I've learned a ton and found it to be very easy.

I really like this digital site glass concept. I have been thinking about the various ways to do this and pressure sensors were certainly one of them. I really like Bull's use of the ultrasonic sensor and I think that's probably the way to go. Bull, can it read through a lens? If it can read through a lens then it could be isolated from the steam and reasonably insulated from the heat. The only advantage I see with using the pressure sensor is that it can be remotely mounted and connected via tubing.

-Derrin aka Backyard Brewer

 

[LooyvilleLarry]

I should have two of these in my hands on the 17th ! Maybe even get to try them out that weekend or around Christmas. I'm thinking this would not make a good New Years project

 

[ajwillys]

Just to throw out an alternative solution you could use a float in a traditional sight glass with a series of infrared emitters and sensors.

What about if you did something like this with a float but instead of a series of IR pairs, you just had a laser rangefinder (distance measurer) mounted to the top that would measure the precise distance the float is away from the top. This way, you would have digital and analog in one sight glass. :cross:

EDIT: Just a quick search, but I'm thinking something like this:

http://www.acuitylaser.com/AR200/index.shtml

 

[Brewers Hardware]

What about if you did something like this with a float but instead of a series of IR pairs, you just had a laser rangefinder (distance measurer) mounted to the top that would measure the precise distance the float is away from the top. This way, you would have digital and analog in one sight glass. :cross:

EDIT: Just a quick search, but I'm thinking something like this:

AR200 laser measurement sensor overview

I think you'd have a difficult time making sure the float was your target and we're back to wondering if the laser rangefinder would live in the environment.

Instead of a series of IR pairs, which would require a lot of wires to decode which pair, I was thinking of a series of small magnetic reed switches with a resistor array and have a small magnetic float. I was thinking of the reeds in a glass tube and a magnet on a foam donut around the tube. You would wire one side of all the reeds to a common and then each in series with a different resistor value and then to the sensor wire. The schematic would look like a ladder with a reed-resistor pair at each rung. Each closed reed would result in a different resistance across a single pair of leads and could easily be measured by an Arduino or similar.

For an external version, you might be able to float a small spherical magnet on top of a small float in the tube and then have the reed array glued to the outside of the tube.

The reed switches I'm thinking of are only about 1/2" long so you should be able to get 1/2" resolution. You could probably etch a long skinny circuit board and take advantage of SMD resistors

The ideal way to pull off a digital site glass would probably be with the capacitive technology they use in a lot of sending units. They work with an electrode in a tube that floods with the liquid being measured. The tube has a known capacitance and the liquid becomes an electrolyte. Flooding the tube changes the capacitance and the resulting measurement is converted to the level. They are expensive though and I wouldn't know how to make one.

 

[bull8042]

1/2" resolution I don't think is going to be good enough. In a keggle, that is approaching 1/2 gallon. Of course, it really depends on just how accurate you want to be.
As for the laser idea, it would work and be very accurate, but you really want to price them before you decide. The ones we use are several hundred dollars!

 

[ajwillys]

As for the laser idea, it would work and be very accurate, but you really want to price them before you decide. The ones we use are several hundred dollars!

Oh yeah, I'm sure it would pricy. There's one on ebay right now for $300 obo (I didn't know ebay did that). The coolness factor of having digital and analog in one glass would be frickin' sweet.

 

[Brewers Hardware]

1/2" resolution I don't think is going to be good enough. In a keggle, that is approaching 1/2 gallon. Of course, it really depends on just how accurate you want to be.
As for the laser idea, it would work and be very accurate, but you really want to price them before you decide. The ones we use are several hundred dollars!

I agree it's not ideal. In my kettle I'd only get closer to 1G resolution. But it would live in the enivornment and only needs 2 wires to work.

When I get some extra cash I'm going to pick up one of those ultrasonic sensors to play with.

 

[bull8042]

I agree it's not ideal. In my kettle I'd only get closer to 1G resolution. But it would live in the enivornment and only needs 2 wires to work.

When I get some extra cash I'm going to pick up one of those ultrasonic sensors to play with.

Sometimes, simplicity is the dog's bollocks. I haven't tried the ultrasonic yet either. Hopefully, I can get enough brew on tap to last me long enough to take my system down for a bit to try it.

 

[BrewBeemer]

1/2" resolution I don't think is going to be good enough. In a keggle, that is approaching 1/2 gallon. Of course, it really depends on just how accurate you want to be.
As for the laser idea, it would work and be very accurate, but you really want to price them before you decide. The ones we use are several hundred dollars!

bull; on my Anheuser Bush 15.5 gallon kegs after doing one gallon fills with three different one gallon containers tested three times I came up with 1 1/4" height increase per/gallon added inside the keg. When across a roll ring it changed that measurement.To the brim measurement with the spear removed the error from three different gallon containers was only 2 oz and less. To the brim spear removed was exactly 2,000 ounces. Different manufractures of 15.5 kegs will have a slightly different diameter, this can be up to 3/8" in diameter. I recall the Jack Daneils keg was made in France. Did you know Jack made Bier? 1994 to 1997 only then quit and stayed with the hard liquor. A collectors item?

I have one rather clean Firestone 15.5 keg with the rectangle embossed windows on the skirts top and bottom. This is untouched with app 15 psi inside but empty. For someone that wants all their kegs to look the same by manufacture i'm looking to swap straight across for a same condition Anheuser Bush 15.5 keg so my kegs also are the same looking. Only thing involved would be shipping a same price swap for both parties by UPS ground.
Later........Carl...........

 

[bull8042]

Hey Carl, good to hear from you again.
I guess your measurements would translate into 1/2" = 0.4gal. You brought up a point that I had yet to really consider. It is going to be very difficult to get an accurate volume measurement using distance because the vessel is not "linear". ie, 1/2" volume in the bottom is MUCH different than 1/2" in the middle of the keg.

 

[Brewers Hardware]

Hey Carl, good to hear from you again.
I guess your measurements would translate into 1/2" = 0.4gal. You brought up a point that I had yet to really consider. It is going to be very difficult to get an accurate volume measurement using distance because the vessel is not "linear". ie, 1/2" volume in the bottom is MUCH different than 1/2" in the middle of the keg.

I hadn't thought about that. Once you figure out what each distance correlates to, it's pretty easy to write the calculation in the code. I have a straight wall kettle though, so I'm not worried about it.

 

[phillc]

I just received my pressure sensor. I will be working on this soon. I have completed my digital temperature probes as well including most of the code. This will all be going live at the same time. I am using an Arduino board with a 20x4 LCD. So far, so good. Temperature will come from all three vessels. Volume will only come from the HLT and Kettle. I don't really see the need for volume measurement in the MLT as I will know how much went in, and how much comes out.

 

[diatonic]

Can't you just measure the pressure somewhere low?.. like the bottom connection of a traditional sight glass?.. maybe even bring the sensor down to the same level as the bottom of the kettle (more difficult to clean). Variances in SG would make it difficult to be precise, but if you knew your pre-boil volume and SG you could plug that in to your software knowing that what is boiling off is 99% water and it could compensate for the SG change as it boils off. You'd be measuring mass instead of volume but I would think it would get you close enough.

 

[phillc]

Can't you just measure the pressure somewhere low?.. like the bottom connection of a traditional sight glass?.. maybe even bring the sensor down to the same level as the bottom of the kettle (more difficult to clean). Variances in SG would make it difficult to be precise, but if you knew your pre-boil volume and SG you could plug that in to your software knowing that what is boiling off is 99% water and it could compensate for the SG change as it boils off. You'd be measuring mass instead of volume but I would think it would get you close enough.

The sensor won't even be in or near the vessel. In my case, there is a 1/2 inch port welded into the side, attached to a 90 degree fitting, attached to a length of SS tube, attached to a rubber hose, attached to the sensor. Super easy to keep everything clean, and the sensor is never in any heat/moisture danger.

Corrected SG is necessary for the most accurate value, but I don't think it is that huge of a consideration for this application. I will be doing my homework, however, and this will be considered in software.

 

[zakleeright]

Hi PhillC, Yuri, et al;
Coming across this two years late, but wondering if any progress has been made? Did those Freescale pressure sensors work with your Arduino? Has anyone come up with a working "Digital site glass"?

 

[Sawdustguy]

Hi PhillC, Yuri, et al;
Coming across this two years late, but wondering if any progress has been made? Did those Freescale pressure sensors work with your Arduino? Has anyone come up with a working "Digital site glass"?

Go to the Brewtroller site (www.brewtroller.com). It works with the brewtroller using a bubbler system.

 

[zakleeright]

Thanks! Lots of good info on your brewtroller site. Like you and Yuri, I'm interested in using Arduino to control brew processes. Unlike you guys, I've only been playing for a couple months now - I have it opening valves, and controlling 120/240VAC, in response to temp. readings, which I'm displaying on an LCD. Have two Arduino's communicating via the I2C bus, etc - proof-of-concept stuff...
Cheers

 

[Zaphod]

Thanks! Lots of good info on your brewtroller site. Like you and Yuri, I'm interested in using Arduino to control brew processes. Unlike you guys, I've only been playing for a couple months now - I have it opening valves, and controlling 120/240VAC, in response to temp. readings, which I'm displaying on an LCD. Have two Arduino's communicating via the I2C bus, etc - proof-of-concept stuff...
Cheers

Hey zakle, you have your code posted anywhere? I'd love to see it. I'm going through the same independent process right now. I'm a ways behind you as I have my arduino reading in temps from a couple one-wire sensors and displaying it on 20x4 LCD, that's all. Thanks!

 

[zakleeright]

Sir Beeblebrox,
I do not have them posted, but am certainly willing to share what I've done. I'm not much of a programmer, but fumbled around enough to get some proof-of-concepts working. Where's an appropriate place to post that stuff?

 

[Zaphod]

That's a fine question. If you want to post it publicly, you can try out Google Code:
http://code.google.com/hosting/
Considering the arduino installs themselves along with plenty of other arduino projects are hosted there, I figure it's probably a good place to try.

 

[zakleeright]

I've uploaded my crude code here.
http://code.google.com/p/arduino-brew-poc-v1-0/downloads/list

I'm not a programmer, so critique, better methods, etc are very welcome.
cheers