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Stoker or homemade temp control??

Discussion in 'Reverse Flow' started by aero-q, Sep 30, 2010.

  1. I just completed the conversion of my unit to a reverse flow (was a single pass).  Test fire and cook last weekend.  MUCH happier with the overall temperature distribution across the full length of the grate.  It's about 20 degrees end-to-end.

    Now that I seem to have my arms around that, I want to move to the next level and better control the temperature over time.  Of course that takes me to a STOKER unit....if I want to pay that much.  I know there are others, but the Stoker seems to float to the top as fas as dependability, accuracy and flexability.

    I am asking for your opinions and experience regarding a homemade version versus the purchase of a Stoker?  It's easy to get a PID temp controller, cheap power supplies, fans, thermocouples, etc on the internet. I am plenty handy with all the electronics and wiring.  Making one adds up to less than the cost of a Stoker.  PLUS you get the satisfactions of saying "I built it myself" when others see it.

    Please chime in and tell me your thoughts!!
     
  2. bigtexun

    bigtexun Newbie

    This is just an opinion at this point...  But I'm asking the same questions you are.

    I think a PID would be fast and easy... too easy.  And while it might impress guests with your savvy, it isn't much of a challenge.  The PID is designed to control industrial processes, and is intended for tasks like controlling temperature.  It will self calibrate the needed output to maintain the set temperature.

    Going the other way is a bit more fun.  I want something that I can hit with a web browser on my smartphone, and that will send me text messages when it needs attention.

    I'm the lab manager for a company that makes network equipment, and I have 5 HVAC systems, and a roomful of servers to monitor.  After I had all of my critical servers being monitored and graphed, I moved on to instrumenting my HVAC systems.  I used 1-wire sensors.  When I stumbled across the Stoker, I realized right away they were using 1-wire just like I did at work, and suddenly everything seemed so easy.

    The only problem is that the sensors I use, while really accurate, cannot handle grill temperatures.  So instead of using precision temperature sensors, the best solution appears to be thermocouples and digitize them with a 1-wire chip designed for making smart li-ion battery packs.  The chip has a high-precision volt meter that is designed for measuring small voltages. 

    The 1-wire bus is really 2 or 3 wires (depending on how you want to implement it, and how far you want the wires to run).  You can put a large number of sensors and output devices on the one bus, there is a family of chips for this.  I read my bus with OWFS, (one wire file system).  Owfs is Linux software that creates a folder representing your 1-wire bus, in the folder are folders named with the serial numbers of all of your devices on the 1-wire bus.  In each device folder are files, each representing one of the viarables in your sensor.  For stability, I start Owfs, copy all of the data out of it, then shut it off, each time I read it (something I figured out at work to solve 1-wire chip stability issues). 

    A voltage from a battery charger chip will need to be converted into the temperature, but that should be some fairly easy math.  But each sensor will probably use a slightly different conversion formula that you derive from calibration in boiling water.  I haven't done this part yet, but it will be a simple script using BC (basic calculator, another linux app).  I'll drop the temperature values into something that makes graphs on web pages, and has logic to send pages and trigger output devices to do things like turn a fan on and off.  There are dozens of ways to do this.  I've used many of them, you can do anything from shell scripts, to something like Zabbix.  Zabbix does the web graphing, notifications via text or email, and it can trigger events based on complex (or simple) criteria.

    A PID doesn't just turn a relay on and off.  Temperature overshoot would be a big problem for industrial processes, so a PID will generally do things like pulse a relay on and off with long or short pulses to prevent overshoot.  It figures out how to do this in a calibration run that you must perform before using the unit.  Your homebrew system will require a manual calibration.  This will probably be time consuming, but your investment in time will be part of your investment in this system.

    I still have some details I'm working through...  The 1-wire bus can go a really long distance, so I can use a computer in my home office to run the whole thing...  But I could also use a small computer like a Beaglebone or Raspberry Pi.  I have samples of both of these in my box of toys, but they may not have enough umph to run a system like zabbix.

    I don't know about your grill, but mine has a problem with overshoot.  Once the temperature is too high, you can drop it down by closing the damper, but it is so well insulated that the fire is out before the temperature is low enough to let the air back in.  So preventing the overshoot will be important.  Each grill will probably need different adjustments to the software, I know the Stoker is sold as a kit for each model grill, so that the air control has the right fit, but possibly because they have slightly different

    But yeah, you and I are just 2 of dozens of people asking the same questions.  Honestly the stoker isn't so expensive to justify the work, but if you need a hobbyproject, putting the bbq on the Internet is a  geeky-fun thing to do.
     
    Last edited: Oct 6, 2012
  3. Sounds like a cool idea, Aero-Q. Go for it. Keep it simple and build it yourself, there's nothing like the feeling of "done it myself".

    Just a thought for bigtexun. You're planning of running this 1-wire bus all the way from the grill to your home office? Why not build a wireless module to attach on the grill. You could have WLAN or Bluetooth or some other radio standard that fits your needs. This way you'd just have to code some firmware for the module and an app for the phone and connect directly to the grill from the phone. If you put a WLAN access point on it and configure your home router properly you'd be controlling it from work in no time.

    Cheers /Wes
     
  4. bigtexun

    bigtexun Newbie

    A very good suggestion!

    Connecting directly from the phone to the sensor would skip a lot of infrastructure steps. 

    However as simple as it sounds, it might actually be more work.  By using the existing sensors, applications and infrastructure, I'm limiting the work to configuring existing systems.  Your suggestion has a lot of merit, but it might require a lot more software work.  I would need to code up an app for the phone.  I've not done that before, but it wouldn't be a bad thing to learn how to do.

    On the surface, your suggestion does seem simpler. 

    In fact, if we didn't already have Internet, text messaging, email, your suggestion would clearly be the simplest solution.  But connecting a computer to a phone is very simple, all I have to do is write a script to send email to a special email address, and it shows up on my phone as a text message.  And any web page can be viewed by my phone, so the infrastructure to the phone already exists.So I don't have to do anything to get that side of things working.  My phone came with that capability, as did every computer I use.  So I already have a universal communications system at my disposal.

    But to address your point on avoiding the wire, I have some zigbee modules that could wirelessly transmit the sensor data, to skip the wire.  But the phone would need drivers and an app to talk directly to that, and there is a range problem.  The best range my zigbee modules can do without a communications tower is a couple blocks.  Not bad, but it won't make it to the grocery store or my office.  And I would have to add a zigbee module to the phone.  If I use wifi or bluetooth, the range is shorter, and I still must put a computer somewhere to make the sensor talk.  I would still need a computer to read and process the temperature data, the wire lets me leave the computer in the office, rather than putting it outside by the grill.

    The stoker is a great example of using existing infrastructure to keep things simple.  Stoker uses wifi to get to the Internet.  From there they use existing infrastructure.  The difference between my plan and stoker's is that they use twitter, and I plan to use email and text messaging.  It is a difference, but not a huge difference.  It is more complex than the path you suggest, but your path would require more work, and may well have a limited range that would reduce usefuleness.  My phone's bluetooth has a range of a few dozen feet, my phones wifi has a range of less than 100 feet, and other technologies would require hardware be added to the phone (like zigbee).

    my phone can already talk to any internet connect pc. so I had planned to use that path.  All I must do is get that PC set-up to control the bbq pit, and communicate what it is doing to the phone.  So while it may seem more complex than a direct path from the phone to the grill, it will take less work.  The cool thing about the web page is that I can also let the phone send commands to the grill, so I could easily adjust the temperature, or shut the system down.  Having the range to communicate to me while I am at work 15 miles away means that I can have the system tell me to come home to fix a problem such as running out of fuel.

    So while it seems like my plan is complex, it is simple frim the point of view of the work that is required.

    Bur the PID is really the simple solution.  The PID is cheap, and is already designed to do the required task.  It just isn't as much fun as putting the grill on the Internet.

    I actually like the design of the stoker.  And the cost is very reasonable.  The only reason I would do my own is because I can, and sometimes doing things the hard way is more fun.  I can go to a restaurant and buy great bbq that has been in a smoker for 24 hours, one of the best restaurants is only 10 minutes from my house.  The reason I would design my own stoker clone, and do the work of operating my own smoker is because it is hard, and because I can.  Your suggestion raises the bar a bit and would be harder still...  So it does have a lot of merit.
     
  5. Indeed "just because I can" is an excellent reason for doing it. Can't agree more.[​IMG]

    I had never heard of the Stoker prior to this thread. Checked it out and it looks like it has all the bells and whistles and then some. I have previously been sketching on a wireless temp monitor module where I could connect a bunch of regular meat thermometers for monitoring remotely. The main idea was to put together a wifi module with some simple development board. Arduino have nice boards but they are a bit expensive. Can't say I have checked the market too well yet. The module would then publish a simple interface over wifi through my wireless home router for easy access over the internet from a phone app or some other web based service. Trying to keep it simple on the BBQ side and focus the brains in the remote app sort of. That concept could be extended for temp control with proper hardware on the bbq side. The basic idea is the same.

    Hmm. Think I need to get this going during the winter.[​IMG]

    Cheers /Wes
     
     
  6. smoke_chef

    smoke_chef Smoking Fanatic SMF Premier Member

    WOW... I mean WOW... you guys make this sound easy. It's all over my head but sure is interesting to read. I'll stay tuned to find out what finished product you come up with. With me knowing nothing about nothing when it comes to this stuff... I can just add that the idea of controlling the fire or getting alerts via my phone is fascinating!! I would love that! Very cool you guys... Very cool.
     
  7. jwbtulsa

    jwbtulsa Meat Mopper

    Yeah. What he said.

    Don't need to know how it works. Just want to spend the money on the technology for my own convenience. I'm linked to my iPhone 24/7 due to my job in the ER. Would appreciate the opportunity to take advantage of it when I am smoking good eats. Cool graphical and control integration would be enough for me to justify an iPad.
    iBBQ, therefore I am! Ha ha
    Keep us posted. You build it, I can invest, we are all happy (and well fed)

    I have to admit, I love taking the day off to hang with the stick burner. Everyone leaves me alone!
     
  8. bigtexun

    bigtexun Newbie

    Connected to the phone for your work in the ER?  That sounds like just too much fun.  I used to work for a large hospital chain, and I had 10 ER's keeping me up all night...  No time for BBQ!

    For those of you following this thread without the desire to build something on your own, the Stoker is the thing to get.  It uses twitter to send you alerts to your phone, and it has a web page you can put on the net as well.  I don't own one, so I can't attest to how much work you may need to do to be able to access that web page through your ISP.  It may require dynamic DNS and firewall configuration to get the address mapped to the Internet.  If you have a static IP, it is easy, if your ISP changes your IP from time to time it is more difficult.  Regardless of that, the Stoker is everything I aspire to build on my own, without the work.

    You will find the Stoker at www.rocksbarbque.com.  They have kits for common grills, and can be adapted to just about anything that you have the wherewithal to work with.  A kit for a small system price starts around $330, and the stoker is capable of running a large number of grills with some simple expansion because of their use of the 1-wire components...  They did it the way I would do it.

    The caveat to the Stoker, and any other control system, is that you have to have a grill/smoker that has good air control.  If you have too many air leaks, or other design issues, a Stoker type system may not help much.  But they have a list of grills they directly support, so you can use that as a buying guide if you want to start off with something new.

    As for the Stoker-clone work...

    Last weekend I did some tests with the sensors I use at work, and they work really good, but those sensors are only good for low-heat applications, the first time they encounter high heat or flames they will die.  I have a couple nice thermocouples that came with the wireless bbq temperature monitors I have, so my next experiment will be to pair a thermocouple with a battery pack controller chip that uses the 1-wire interface.  It's a good excuse to do some more bbq... 

    I think that for my homebrew system, I'm going to focus on a multi-probe system, at least three probes to measure the smoker temp, so that I can average data from more than once source.  I'll also use one or more probes for insertion into the meat, so that I can track the meat temperature.

    I'm also thinking about automating the lighting of the fire itself...  Nothing would cooler than getting the grill warmed up while I'm at work, so that by the time I get home the temperature is stable at the desired cook temp.  I've heard that there are smokers with propane based self-lighting systems...  Electric is another option.  Electric would be easier to control.  They make electric charcoal starters, but you might be able to mount a electric water heater element on the side of the firebox... and those parts would be easy to find, so as you ruin elements you just slap in a new one from the hardware store.

    A secondary advantage of the automated fire starting mechanism is being able to relight the fire if it goes out.  My grill is so well insulated that if I overshoot the temperature by 30 degrees, the fire will go out before the grill has cooled to the desired temp.  So overshoot is a problem to be avoided, unless you have a self-lighting system. 
     
    Last edited: Oct 10, 2012