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Computer/PID controlled vs manual controlled Bread machine-heat gun roaster?
I am in the process of designing a bread machine heatgun roaster. I am trying to decided whether I want to go for a manual or computer/pid/ardiuno controlled roast.
I would totally go for an automated roast for the hands off approach and the ability to more precisely control the roast profile, however, I don't exactly know where to start.

On the hardware side, I am comfortable with retrofitting a machine (I've seen some pretty inspiring designs on here), and should be fine with doing some basic rewiring(ie to keep the motor running, disable temp sensor)

On the software/automation side:
I've read a lot about PIDs and how they work, and I've read about the roast logging software and how you can log and design roasts, I understand that you can use an ardiuno to control roast temps, I know that you need relays and such..but I don't exactly know how all of that fits together.

I guess my big questions - how does the manual control compare to automation in terms of roast quality?

Does anyone have a guide to building a PID/computer controlled heatgun
If it was me, I would go manual and learn about roasting first. Then you can try the PID stuff. I tried going auto control and found myself taking over manually too much and went back to manual.

I do use a logger but only to monitor the roast.

KKTO Roaster.
As for bread machine heat gun setup, I suspect if you go to the building roaster section and do some searches, you can find info on the, but I can't help you there. Never tried a heat gun or a bread machine.

The PID control using the Arduino UNO and the TC4 Shield, that I do know a little about.
As for marrying a PID to a heat gun bread machine setup, since never used one, not sure how particle it would be. To be able to control the heat, you would probably have to separate the heating element from the motor so the heat can be controlled seperatly. Then you would have to make sure it has an AC motor that will run separate from the heating element. You can just have it where the PID controls the whole thing but fan speed changes with the heat.

As for the PID, don't think for a second it's going to be a magic box that you just hook it to your heat gun/bread machine and now you have automatic control. It ain't gonna happen quite like that. There is right smart of work and a pretty good learning curve involved to connected a TC4 to it and making it useful for anything more than a data logger.

You mentioned the TC4. There are two version of the TC4. The TC4C is a stand alone board that does not need an Arduino board to work. Then there's the TC4 Shield that has to piggy backs on top of an Arduino UNO 3 board to work. The main difference in function is AC motor/fan control. The TC4C will not provide connection for the Zero Cross Detect (ZCD) to control and AC motor, such as trying to control you whole heat gun. If your plans are to control an AC motor, the you have to use the TC4 Shield, the Arduino UNO 3 board, the ZCD module, and a -10 SSR. For the heat side, you would use an SSR and at least one thermocouple. That will either be inserted into the bean mass or monitoring the exit air. You can have thermocouples in both, bean mass and exit air and it will monitor both and you can use which ever you want for control. Thee is also and LCD module you can get to interface with either one. Understand also, it will come as a circuit board, either with everything soldered on or as somewhat of a kit, which ever way want to go. There is still assembly required and pieces to order to make it functional. It's not even in a case, like I said, it's a board/s and some assembly is required. There is a schematic available for typical wiring setup.

If you only need/plan to control the heat, then the TC4C will work, as well as a dozen other devices, that are supported by the Program you plan to use to monitor and chart the roast with.

Also, if you only plan to control the heat, you might want to look at a PID that has auto tune. Getting a manual tune like the TC4 set up can be a bit of a challenge. Not saying some auto tunes can't be also, but a good one that works will make life simpler.

RoastLogger and Artisan are the two programs you are going to here the most about because they are free and open software, and there are people on here that support them. If you go with a generic PID, look at Artisan and see what it supports. If you go with a TC4, you would use RoastLoggerTC4 PID or aArtisanQ_PID 5.3.
I would rely on JackH's input on this issue. I have no experience with 'bread machine/heat gun' roasters, but I have over 7 years experience home roasting (fluid-bed) and 26 years experience as an Electrical Controls Engineer.
My roaster has a PID temperature controller. However, I always run it in manual (%output) mode because it's easier for me to control the roast via blower speed using smell, sight, sound, and time.
When I first built my roaster I thought I would use an Allen Bradly SLC504 to run it. Although the SLC 504 is capable of running about anything using as many PID loops as you feel like programming. It just wasn't necessary to roast great-tasting coffee.
No oil on my beans...
I agree with Jack as well. You must be able to control the beans manually before you try it with your computer...


That sounds a bit beyond me at this point. I'll keep looking into options - maybe i'll start with the basics(manual control) first.

@JackH and @oldgearhead
For the manual control, do you use/recommend something like a router speed (or in this case, voltage) controller to control the heat gun heating element? Are you doing real time monitoring of temps with computer interface and trying to match the roast temp to a pre-set profile or just going off of smell/prior experience?
I would start with a tempperature probe, an SSR and one of these:
No oil on my beans...

with that PID, you are still doing manual control of temp through out the entire roast, OR do you just set the PID to the max desired temp(ie 220 C) and program the PID to achieve the desired Rate of Rise.
I kinda figured you would see it that way, that's why I wanted to make sure you knew what you were looking.

As the others have mentioned and I tried to explain. PID sounds great when you think about it and read about it but it's a whole lot more complicated than you have dreams of it being. Sounds easy, just connect it, program it and let it control the roast. Well, like I said the first time, it's not a magic box and not as easy as it sounds, far from it.
Check out Artisan Visual Scope and the list of devices it supports. See if one of those devices has PID capability, will control an SSR or can handle at least 15 amps and will monitor two thermocouples. If it's expensive, forget it and just get a cheaper one that will monitor a couple K or J type (K being the more common) thermocouples. Plan on just using it as a input device so you can chart your roast on Artisan, so don't go spend bunches of money on one. Later, if as you get your feet wet and feel like you really want to try using a PID, you have one you can start playing with.
Now, for heat control, I'm sure there are a number of manual controls available, but I've never used any so someone else will have to tell you how they do that.
I have a degree in electronics and never do anything the simple way, so when it starts getting simple and logical, I find a way to complicate the crap out it.
Edited by BenKeith on 02/04/2016 4:22 PM
I've been BMHG roasting for at least 5 years now. My setup is pretty simple, although I've added in chaff collection.

I'm not saying it's the best, but it works for me and I can roast in the winter.

I'm not saying you have to do this, but it's one thing I've done that helps a lot.

I used to vary the height of the heat gun. Too much work and didn't really allow for much other than wasted energy.
I then tried a static location where I cycled the heat gun from high to low and also tried on and off (not recommended because it burns up the guts faster). The high and low speeds were okay, but trying to watch a timer, log the roast and switch the switch on the heat gun got to be like one of those "one man band" setups. I missed things, burnt my hand, didn't have repeatable logs etc. It was really just too much to do at once.

So now, to fast forward, I have a chaff collector which sucks the air out of the top of the machine. This also has a cooling effect. I run the HG in full/high mode and increase the airflow if I need to slow things down.

I have a very unique DIY with harbor freight heat guns (yes, they burn up often on me) some piping hooked up to an old kirby vacuum motor that collects chaff into a DIY cyclone/bucket and exhausts out my roof. I use a router speed control to dial down the vacuum motor for my needs.

I found an old photo.

Not much has changed except I enclosed the bottom area with plexi glass and ran the pipe out through the roof instead of to the right. The cooler is in the bottom, and I simply plug it with a lid to make the suction for collecting chaff, then after I dump the beans into the cooler (collander in a bucket) I plug the other end so the air is drawn across the beans.

I'm also profiling roasts now using roast logger and a computer with ocr/camera. My thermocouple is on the heat gun mount(it rotates up and lays flat to pull out the bucket)

Been doing things this way for almost 3 years now while I slowly build my fluid bed roaster.
Man, just realized how old that photo is. I haven't had an orange HG for quite some time.
I like it!!

How often are you recording temps - are you manually writting down/typing temps at different time periods - like every 30 seconds?

what is this about ocr/camera?
Edited by ginny on 02/04/2016 5:22 PM


BenKeith wrote:

If it's expensive, forget it and just get a cheaper one that will monitor a couple K or J type (K being the more common) thermocouples. Plan on just using it as a input device so you can chart your roast on Artisan, so don't go spend bunches of money on one

I may just do that for now - logging+manual heat control would probably be a good first start.


johnv wrote:

I like it!!

How often are you recording temps - are you manually writting down/typing temps at different time periods - like every 30 seconds?

what is this about ocr/camera?

Well a fluid-bed roaster is a lot different than yours.
a fluid-bed kind of has it's own profile because beans get lighter as they roast.
To answer your question, I set the heat by using manual control (%output). I set the heater percent output based on the ambient temperature and the test weight of the beans. During the roast I lower the blower speed 2-3 times based on the roasting progress and total time. I always aim for a 12 minute roast. Heat gun elements produce hotter air as their flow rate decreases....I do not plot the roasting temperature because I know what it is at every blower setting. I only note the bean temperature to make sure the roast ends at about 420 DF. However, I do monitor the blower inlet temperature to insure my recycling chamber is performing correctly.
Edited by oldgearhead on 02/04/2016 7:42 PM
No oil on my beans...
If going with just Data Logging. Do the e-net searches for Artisan Visual Scope, there is also a long thread under Data Loggers on this site. Do a little reading and learning. You can find K-Type thermocouple monitors for less that $30 but they are not going to do you any good trying to use them with Artisan if it does not support them. So, before investing in one, make sure Artisan supports it. If not, you will just have a device that will give you a digital read out of your temps.
As for OCR, that's Optical Character Reader and uses your Web Cam. That's as far as my knowledge goes with that, and I wouldn't promise that little bit of info is accurate. Never tried to use that method either, but several do. That gets around having to use high price PID monitors etc, needed to interface with Artisan. A cheap one with USB output fed into your computer to display on the monitor and I think Artisan and RoastLogger (another charting program) will read it off the screen, no interfacing needed. Again, never used it so someone else probably has better info on that method.
I'll second, third or fourth, wherever we're at now, the recommendation to go with manual control until you get a good feel for the whole process.

I'm coming up on two years since I built my roaster and it's still going strong. I do 4-5 3/4 lb (green) roasts weekly and I am still using the original HF heat gun and speed controller and I honestly couldn't be happier with the final product.

I'm also very pleased with the RoasterThing software and usb thermocouple interface. The software is free and very comprehensive, the interface is $100 and provides inputs for two thermocouples, although I've only ever had the need for one. You can usually find nice Omega Type K thermocouples on Ebay for $20 or less.

My build is in the Bread Machine sub-forum titled "My Winter Project"


MerlinWerks wrote:

usb thermocouple interface

My build is in the Bread Machine sub-forum titled "My Winter Project"

How exactally do you connect the thermocouple to computer?
do you get real-time temp logging/monitoring with that?
The thermocouples plug into something like this and it connects to the USB port on the computer.
If it's not compatible with your data logging program, then you have to go to something like the OCR to get them into the data logger.

The one I've given the link to is compatible with Artisan so it would read directly into Artisan. Now this is not a PID, it just reads the thermocouples

Also the thermocouples can cost from several dollars to $50 each. Depending on who's and what kind you buy.
Edited by BenKeith on 02/04/2016 10:13 PM
I have this thermometer(see link) - picked it up at a neighboring labs going out of business give-away.


It's high quality and has a nice probe, So I might just go with the OCR and roastlogger software. I have an extra android phone that I can convert to a dedicated webcam as well.

I've got a thrift store bread machine as well as a heat gun and router speed controller on order - Hopefully I'll get some pictures up in a new thread as I start building and testing.

Thanks all for the help so far.
Edited by JackH on 02/05/2016 10:06 AM
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