Any interest in starting new open source automated brewing project...for propane?

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Does this seem like a good idea?

  • Yes, this sounds awesome!

  • No, this sounds idiotic!

  • You'll shoot your eye out, kid!!!


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jrubins

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Hi all,
I'm wondering if anyone else would be interested in contributing to an open source automated brewing system that uses propane for heat. I'm interested in doing something similar to the HABS (halfluck automated brewing system), however I want to use propane as my heat source. I also want to do *real* PID control on an Arduino (most electric and even gas systems are just PI control).
Using an adjustable regulator with a servo to control the regulator should get me close. I've been experimenting a bit with different materials, and I'm thinking of hacking a servo and using something like this to replace the motor http://www.ebay.com/itm/261146607144?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649 and a 10 turn pot to replace the pot.

Any thoughts? Anyone interested in contributing?
 
One factor to consider is that the PID model assumes a certain linearity of response that it is going to be difficult to get from twiddling the regulator. Better to cycle the gas on for x seconds, off for (10-x) seconds, using a solenoid valve. My $0.02.
 
This sounds interesting. What kind of gas valve are you planning on using? How are you going to link the gearbox to the valve?
 
One factor to consider is that the PID model assumes a certain linearity of response that it is going to be difficult to get from twiddling the regulator. Better to cycle the gas on for x seconds, off for (10-x) seconds, using a solenoid valve. My $0.02.

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).

Solenoid gas valves are also quite a bit pricier than adjustable propane regulators. though by the time I'm done messing about, it may not be any cheaper :)
 
This sounds interesting. What kind of gas valve are you planning on using? How are you going to link the gearbox to the valve?

The gas valve I'm using is my adjustable regulator on my turkey fryer (at least for version 0.0)
http://www.newegg.com/Product/Produ...GoogleMKP-_-pla-_-BBQ+Grills-_-9SIA0FU0DY4544


My idea is to attache the motor to the regulator knob by making a custom fitting out of shape lock
http://shapelock.com/

This may involve removing or not the actual plastic knob.

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.

Here's my inspirations:
HABS
http://arduino.cc/forum/index.php/topic,8598.0.html
http://www.halfluck.com/source/

Frankengriddle
http://www.weirdstuffwemake.com/weird/stuff/food/tools/frankengriddle.html


One-ton linear servo
http://makeprojects.com/Project/One-Ton+Linear+Servo/882/1#.UPWhoqFxe_C

Steam-punk record player
http://www.asciimation.co.nz/bb/2010/11/30/a-steam-punk-record-player
This may seem out-of-place, but it's basically a servo control with hall effect sensors to control a servo motor to open a valve.
replace hall effect tach signal with temperature, change the servo, and bobs your uncle
 
This can already be done with a standing pilot gas valve (or the like). Like Alien mentioned, temp control is much easier with on/off systems instead of pressure control out of the regulator. The temp can be monitored any way you would like (PID, PI, RaspPi, Arduino) and the call for heat actuates the valve for either a preset duration or until temp is reached.

If you are running multiple burners, you will need 1 servo-operated regulator per burner to get different temperatures, if you control the heat that way. Otherwise, a set regulator on the tank side that supplies constant gas and controlled by an automated valve is far easier.

To me, this just sounds like unnecessary programming in a programming heavy operation. That said, I am interested in what you discover.
 
The main advantage that I see is that you can turn up the gas while heating to temp, and dial it back for the boil. This way you can reach temp a quick as possible without cycling the gas during the boil.
 
I have a Bayou Classic control valve similar to this one:http://www.ebay.com/itm/Bayou-Classic-NV108P-1-4-Brass-Control-Valve-for-LPG-Gas-Propane-Burners-/190759875291?pt=LH_DefaultDomain_0&hash=item2c6a2cb2db
I’ll have to play around with it, but I think that I don’t normally rotate it more than 360 deg. Therefore a 360 deg servo might do the trick as long as torque is not an issue.

The Bayou classic needle valves are probably better quality and more 'reproducible' because they can be added on to existing systems (I believe). Unfortunately, I think they require more torque to turn. Could the valve knob be removed and replaced with a gear, perhaps?


This can already be done with a standing pilot gas valve (or the like). Like Alien mentioned, temp control is much easier with on/off systems instead of pressure control out of the regulator. The temp can be monitored any way you would like (PID, PI, RaspPi, Arduino) and the call for heat actuates the valve for either a preset duration or until temp is reached.

If you are running multiple burners, you will need 1 servo-operated regulator per burner to get different temperatures, if you control the heat that way. Otherwise, a set regulator on the tank side that supplies constant gas and controlled by an automated valve is far easier.

To me, this just sounds like unnecessary programming in a programming heavy operation. That said, I am interested in what you discover.

ColoHox, the reason for using PID + Gas control is to be able to hold a specific temperature without the sinusoidal over/under swings that happen with a 'thermostatic' control. On/off is *much* easier, no doubt. But the idea is that I can put in exactly as much energy as I lose to hold a stable temperature over a long period of time.

The advantage of that is (eventually) direct-heating my MLT, HLT, and Kettle.

I *could* go electric, if on/off was a possibility PWM control is easy-peasy with electricity, and that gets *pretty* close, but that requires additional infrastructure that I don't have, and decreases the mobility of my system (since I rent).
 
ColoHox, the reason for using PID + Gas control is to be able to hold a specific temperature without the sinusoidal over/under swings that happen with a 'thermostatic' control. On/off is *much* easier, no doubt. But the idea is that I can put in exactly as much energy as I lose to hold a stable temperature over a long period of time.

The advantage of that is (eventually) direct-heating my MLT, HLT, and Kettle.

I *could* go electric, if on/off was a possibility PWM control is easy-peasy with electricity, and that gets *pretty* close, but that requires additional infrastructure that I don't have, and decreases the mobility of my system (since I rent).

I have a propane direct fired RIMS system and do not have any issues with over/under temp adjustments in any of my keggles. With recirculation and automated valves I can maintain a mash temp for 90min +/- 0.5 degree. Your system would be advantageous during the boil. My burner fires for about 40 min out of the 60 min boil, so a lower, steady heat would be nicer I think.
 
Also, not trying to say bad idea or that my way is best. Just different way to get the same result. Good luck...subscribed.
 
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?
 
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?
 
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.
 
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.ladue/IgnitionModuleAndMassflowController#5157701513186974322
 
tob77 said:
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.
 
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.ladue/IgnitionModuleAndMassflowController#5157701513186974322

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/analogwrite-convert-pwm-to-voltage/

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

@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/2011/04/improving-the-beginners-pid-introduction/

Cool, thanks!


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-Lase...racter_Radio_Control_Toys&hash=item4d0732296d


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-Tuning/PID-without-a-PhD.pdf
 
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.
 
jrubins said:
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

Yes the large mass of water will act as a low pass filter. With a properly designed analog front end for your temp sensor you will not see a very jagged signal. In my system my thermistors only vary by +/- 0.1F so I am seeing very little noise in my signal. Prior to refining my analog front end I was experiencing quite a bit of noise that reached into the +/- 1F range. I also take 5 simultaneous readings and average them out in firmware. I too have an engineering degree and studied feedback control theory in college. In my feedback control lab I experienced first hand how digital PWM control loops can outperform their analog equivalent by a long shot. When the system being controlled has a natural low pass filter in it like we do the PWM output is no different than an analog output and therefore you still can achieve derivative control due to the lag if the system.
 
Yes the large mass of water will act as a low pass filter. With a properly designed analog front end for your temp sensor you will not see a very jagged signal. In my system my thermistors only vary by +/- 0.1F so I am seeing very little noise in my signal. Prior to refining my analog front end I was experiencing quite a bit of noise that reached into the +/- 1F range. I also take 5 simultaneous readings and average them out in firmware. I too have an engineering degree and studied feedback control theory in college. In my feedback control lab I experienced first hand how digital PWM control loops can outperform their analog equivalent by a long shot. When the system being controlled has a natural low pass filter in it like we do the PWM output is no different than an analog output and therefore you still can achieve derivative control due to the lag if the system.


Ok, that makes sense, however, a new electric system >$ than my current propane system, so I'm willing to forge ahead!

Any thoughts on temp measurement devices. You mention thermistors , how about a nice long thermocouple - would that work to give accurate readings without averaging, or am I better off handling that in code?

http://www.alltronics.com/cgi-bin/item/22U013/search/"J"-Type-Thermocouple
 
jrubins said:
Ok, that makes sense, however, a new electric system >$ than my current propane system, so I'm willing to forge ahead!

Any thoughts on temp measurement devices. You mention thermistors , how about a nice long thermocouple - would that work to give accurate readings without averaging, or am I better off handling that in code?

http://www.alltronics.com/cgi-bin/item/22U013/search/%22J%22-Type-Thermocouple

I am not a huge fan of thermocouples for a few reasons.

1 voltage they produce is extremely small in the microvolt range and therefore they are a lot more susceptible to noise.
2 because of the extremely small voltage they produce you need a very high gain and high precision amplifier to get the signal up into the range where an ADC can measure their output. At my last job we had a few products with thermocouple inputs and we had to use a low drift low offset opamp along with 0.1% resistors. Even with that we had to calibrate each amplifier circuit.
3 the way thermocouples work requires you to need a second temp sensor (we used a thermistor for this) to measure the temperature where the thermocouple wire ends. Now any inaccuracies in your cold junction compensation temp sensor cause inaccuracies in your thermocouple measurement.

I prefer thermistors due to their ease of implementation. They can also be accurate enough for our application. I test all of mine in an ice bath and in boiling water and all of them have been within 0.1F. No need for any calibration.

Averaging in code is trivial so I wouldn't worry about it.
 
Yes the large mass of water will act as a low pass filter. With a properly designed analog front end for your temp sensor you will not see a very jagged signal. In my system my thermistors only vary by +/- 0.1F so I am seeing very little noise in my signal. Prior to refining my analog front end I was experiencing quite a bit of noise that reached into the +/- 1F range. I also take 5 simultaneous readings and average them out in firmware. I too have an engineering degree and studied feedback control theory in college. In my feedback control lab I experienced first hand how digital PWM control loops can outperform their analog equivalent by a long shot. When the system being controlled has a natural low pass filter in it like we do the PWM output is no different than an analog output and therefore you still can achieve derivative control due to the lag if the system.

PWM is an approximation of an analog signal that can work very well as long as the PWM cycle frequency is very fast when compared to the system's lag. In theory, PWM can only be as good as analog control, not better. However, we often do not have true linear analog control. For example, the flow through most valves at 50% open is not half of what it is at 100% open. It may be possible for PWM to outperform an analog equivalent because of this nonlinearity in some systems.

Sorry for sounding a little bit like a textbook. I too am an engineer, and I love this ****:mug:
 
Probably most people doing this sort of project would use DS18B20s ("one wire probes") for temperature measurement, e.g.

https://www.oscsys.com/projects/brewtroller/system-design/direct-fired

The digital output is easy to interface and they don't require calibration. Also you can buy probes off the shelf from places like Brewer's Hardware.

But for an open source project you maybe don't have to worry about this at all. People can add on their own temperature measurement routines adapted to whatever sensors they have.
 
Here's a bunch of resources for you on gas valves and controls.

http://wickedstone.com/brewing/Html/gas valves.htm

The basic set up for intermittent (on-off) control is this:

gas%20control.jpg


The off-the-shelf PID controller can be replaced with a Brewtroller or similar Arduino type set up controlling a relay.
 
If you are going the Arduino route, then consider an alternative method, PWM a single solenoid with restriction, and a surge dampening chamber tee'd into gas line to burner down stream to reduce flame fluctuation.
Most solenoids have 100,000 cycle lifetime so I would not expect them to die before the rest of the brew system does and the PWM duty cycle should be in 1/2 - 1 second range which will limit total cycles. For the surge chamber, 2" iron pipe and fittings from the big box building supply should work, start with 12" of pipe and increase/decrease as needed to get acceptable flame fluctuation. Setup would be to adjust restrictor / valve to give max fire with solenoid open 100% of the time and then vary off time to reduce flame level. You should not need a solenoid larger than 1/4" (opening in burner orifice is usually smaller than 3/16"), larger solenoid would be a waste of time and money.
 
Sorry if this has been covered in a previous response, but with regard to the electric vs gas discussion, have you considered using phase angle control? This would allow you to use an analogue control signal to modulate the AC waveform to a heating element. Do a search on eBay for SSRMAN-1P for a solid state relay mounted version.

Having tuned a lot of heating PID loops, I question the need for a derivative term. Depending on the thermal load, temperature loops tend to be proportional gain heavy with a relatively small integral term depending on how well insulated your vessel is. A noisy temperature measuring device will give you hell with a derivative term.

My 2 cents.
 
I think you are right about dropping the D term in general. I do wonder if there are some different issues around tuning PIDs for gas as opposed to electric.

For instance, gas heats the bottom of the pot not the liquid it contains so perhaps it is more important to consider mixing inside the vessel. Poor mixing creates lag and increases the tendency to overshoot, which would make me think about a more conservative setting (i.e. less P). Placement of the thermometer might also be a bit more tricky.
 
I think you are right about dropping the D term in general. I do wonder if there are some different issues around tuning PIDs for gas as opposed to electric.

For instance, gas heats the bottom of the pot not the liquid it contains so perhaps it is more important to consider mixing inside the vessel. Poor mixing creates lag and increases the tendency to overshoot, which would make me think about a more conservative setting (i.e. less P). Placement of the thermometer might also be a bit more tricky.

Definitely, getting the heat measured correctly and uniform throughout the water or wort is important, but that's not unique to gas heat.
I'm thinking of using one of these guys http://www.homedepot.com/Paint-Pain...alogId=1&langId=-1&storeId=10051#.UQFy6UpxerU to keep the temperature uniform. I'm also thinking of using 1 or 2 probes with 3 sensors each to measure the temp at the top,middle, and bottom of the pot.

Sorry if this has been covered in a previous response, but with regard to the electric vs gas discussion, have you considered using phase angle control? This would allow you to use an analogue control signal to modulate the AC waveform to a heating element. Do a search on eBay for SSRMAN-1P for a solid state relay mounted version.

Having tuned a lot of heating PID loops, I question the need for a derivative term. Depending on the thermal load, temperature loops tend to be proportional gain heavy with a relatively small integral term depending on how well insulated your vessel is. A noisy temperature measuring device will give you hell with a derivative term.

My 2 cents.

Phase angle control... that's brilliant! You could potentially just use the arduino to PWM output the angle control without the need for a separate PAC box on the SSR.

Unfortunately, I think that i'm stuck using propane due to my inability or lack of desire to build an electric infrastructure for brewing in my (rented) house.

So, given all that, I'm still thinking servo control of an adjustable regulator is the way to go. I'll order one of these
http://www.ebay.com/itm/330833209709?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
this weekend
and 3 of these
http://www.adafruit.com/products/374
or would these be better
http://www.adafruit.com/products/165

I suspect the digital sensor is better since I can put 3 on a single pin, but it requires the 1wire library, which will take up precious memory on the arduino.
Any thoughts on the tradeoff between physical pin space and memory space for the 'duino?
 
The paint mixer attachment will rotate too fast on the end of a drill. You want to attach it to something low geared like a possibly a mirror ball motor.

Fingers crossed the servo has enough torque. I think either measurement device would be fine. Personally I would go with the DS18B20s because they are calibrated closer (+/0.5 oC instead of +/- 1oC) but better still is the LM35CAZ which is +/- 0.2 oC. Texas Instruments will send free samples if you ask nicely.

Usually people run out of pins on an Arduino before they run out of memory. Another factor is polling speed but given that the PID will be tuned for a sluggish response you probably don't need to take measurements more than every 5 seconds or so anyway.
 
I have been using the one wire thermocouples and they work very well. You don't have to worry about doing conversions and linearisation which will save code. The library takes up a little room, but once the libraries are in, there is quite a lot of memory left for code. You may be able to cut down the library by removing the instruction calls that you do not use.

My recommendation is one wire temperature probes, the ease of implementation and the reduce pin count is gold.
 
Thanks for the advice thus far, gang. The maxim integrated Ds18b20 came today, and my winch servo came in earlier this week. I'll try to find some time to play with these things this weekend and let you know my progress.
 
Just an fyi, $4 each from adafruit is expensive for the ds18x20 or ds1822 chips. Digikey sells them for about $2.10 each.

I just ordered 10 for $10 from eBay. Then I remembered maxim does samples too. :(
 
You could recirculate with a pump to assist in temp dispersion. I use the BrewTroller but have also built Jimmayhugh's Teensy 3.0 system and have used 1-wire on my Mega2560. The 1-wire library is not memory intensive and the DS18B's are excellent. I use the high temp ones that Adafruit sells...they are pricey (http://www.adafruit.com/products/642) by DS18B standards but they are ready to drop right into your HLT or MLT without doing a thing to them.
 
Those high temp ones are a nice option for the MLT. I might experiment with a cheap one, outer cable cover stripped off and replaced with silicone air line.
 
Thanks for the advice thus far, gang. The maxim integrated Ds18b20 came today, and my winch servo came in earlier this week. I'll try to find some time to play with these things this weekend and let you know my progress.

I think that I might jump on board and try this servo idea out as well. I’m debating buying the same servo as you from eBay. Does it look like it’s in good condition? I like your shape lock idea for coupling the servo with the valve. Do you have any ideas on how you are going to mount the servo with the valve? The mount will have to be fairly rigid to avoid any play between the two pieces.
 
I think that I might jump on board and try this servo idea out as well. I’m debating buying the same servo as you from eBay. Does it look like it’s in good condition? I like your shape lock idea for coupling the servo with the valve. Do you have any ideas on how you are going to mount the servo with the valve? The mount will have to be fairly rigid to avoid any play between the two pieces.

Awesome, give it a go!
I'm not sure the servo is exactly what it purports to be. Mine seems to be a continuous rotation servo ... or something has broken within it :)

However, using write micoseconds() does seem to get consistent positioning.
I'm currently working on integrating the sensors, servo, and PID library - each of which is working independently. Once i have that I'll start working on the mounts and such.
I'll probably just use some long bolts and scrap steel to create the rigid mount.

I'll keep you posted.
 
Awesome, give it a go!
I'm not sure the servo is exactly what it purports to be. Mine seems to be a continuous rotation servo ... or something has broken within it :)

However, using write micoseconds() does seem to get consistent positioning.
I'm currently working on integrating the sensors, servo, and PID library - each of which is working independently. Once i have that I'll start working on the mounts and such.
I'll probably just use some long bolts and scrap steel to create the rigid mount.

I'll keep you posted.

Thanks for the idea! This should be a fun little project. Apparently pulses less than 600 or greater than 2400 provide continuous rotation while pulses between 600 and 2400 produce angular position. Is this what you’re seeing? I’m looking forward to seeing you progress.
 
Thanks for the idea! This should be a fun little project. Apparently pulses less than 600 or greater than 2400 provide continuous rotation while pulses between 600 and 2400 produce angular position. Is this what you’re seeing? I’m looking forward to seeing you progress.
yes, i've been using 1000-2000 uS, and that gives me 4 rotations. Once I work out the exact number of rotations I need, it should be good-to-go. That particular servo seems pretty torquey, which is great, since it should allow for full off-on rotation of the regulator.
 
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