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Homeroasters.org » DATALOGGERS - CONTROLLERS - RATE OF RISE METERS » Dataloggers/Controllers/Rate of Rise Meters
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ExTech with Artisan Roast Scope
tra757
My roast chamber is about 3.75" in diameter. The blower sits in a 4" I.D. tube and the chamber sits on top of that inside a 4" duct coupler.

Here is a fan like I use:
www.b757200.com/roaster/IMG_1060.JPG

This is a bad pic of the bottom of the roast chamber. You can see there isn't much of a restriction.
www.b757200.com/roaster/IMG_1062.JPG

Here is the top of the roaster with the chamber off. You can see the top heating element. The air comes out around the outside adn blow the top element there is a hole about 2" in diameter. That sits on top of another element turned upside down so the 2" holes align. So the cold air into the element stack enters around the outside edge of the lower element, passes through the lower element, up into the top element and out around the edge. That is where the restriction is. I have been wanting to replace this element with a single element that is about 4kw and only reduces air flow by 20% or less.
www.b757200.com/roaster/IMG_1063.JPG

Here is the lower half of the roast chamber. The pyrex pipe fits nicely inside the top and the bottom fits inside a 4" duct coupler:
www.b757200.com/roaster/IMG_1065.JPG
 
tra757
allenb wrote:
A couple of questions,

What are the input requirements to the Power brushless ESC, just a low voltage PWM signal and high current DC source for driving the motor? Curious what you are using for the high current DC source.

Second question is what the configuration is for your perforated plate/screen?

Great thread and I think I want to make my next roaster hover as I'm sure Scott is already designing into the MH-1.Grin


I use a power supply from a desk top computer. I use the 5v for circuit power and the 12v for the motor power. I think the 12v side can handle 40 amps. For my next roaster, I have a power supply that is about 4"x8"1.5" and puts out 12v @ 90amps. Smaller, more powerful.

The stainless wire screen lays on top of the perf plate so the beans don't get stuck in the hole of the perf plate. That was happening to me before the screen went in.
 
allenb
tra757 wrote:
allenb wrote:
A couple of questions,

What are the input requirements to the Power brushless ESC, just a low voltage PWM signal and high current DC source for driving the motor? Curious what you are using for the high current DC source.

Second question is what the configuration is for your perforated plate/screen?

Great thread and I think I want to make my next roaster hover as I'm sure Scott is already designing into the MH-1.Grin


I use a power supply from a desk top computer. I use the 5v for circuit power and the 12v for the motor power. I think the 12v side can handle 40 amps. For my next roaster, I have a power supply that is about 4"x8"1.5" and puts out 12v @ 90amps. Smaller, more powerful.

The stainless wire screen lays on top of the perf plate so the beans don't get stuck in the hole of the perf plate. That was happening to me before the screen went in.


I think I read in one of your previous posts that you were using a RC servo controller to produce the PWM signal. I'm assuming you are supplying the RC servo controller with the computer power supply 5 volt output.

Your roast chamber is very similar to a Freshroast but much larger. I think one can get away with less static pressure with this design and still achieve good agitation.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
tra757
Yes, I use 5v for the PWM circuit I built, which is very easy and I would be happy to share the schematic. It emulates a RC servo throttle controller (electric throttle). The ESC takes 5v and the PWM signal and then 12v for the power inputs.

The roast chamber is made up from two of the pieces from old air poppers. Its the thing that the plastic fan screws onto and the pop corn holder fits down into. They were what I had but I could just as easily purchased thin walled pipe of the correct diameter and welded the perf plate in the middle of it.

What gave me the idea to use these fans is an interesting note to this story. When I was roasting with my old air popper and lantern chimney the chaff became a big problem. I was roasting in the shop and the chaff got everywhere. One day I tried using a shop vac to suck it all up. It worked and it worked well. Not only did it take care of the chaff but the smoke too. All the aroma, none of the chaff or smoke. Then I noticed that if I wasn't careful, all my beans would vanish in a split second into the shop vac. When I was able to control it, I noticed that I could load my roaster with lots of beans and get plenty of lift while they were still green. I soon ran into the BTU limit for the charge I had dropped. More BTU's requires more thrust (pressure).

Anyone get a 100mm fan yet?

Tim
 
randytsuch
Not sure if this is obvious or not, but do you control/change airflow during the roast?

You need more airflow at the beginning, when the beans are heavier. As the roast progresses, you can lower the airflow. This will allow you to roast a larger batch size with the same heater, the lower airflow will let you heater reach a higher temp.

BTW, very cool project.

Randy
 
freshbeans
tra757 wrote:


Anyone get a 100mm fan yet?

Tim


Not yet, but it will happen. - Scott
 
tra757
randytsuch wrote:
Not sure if this is obvious or not, but do you control/change airflow during the roast?

You need more airflow at the beginning, when the beans are heavier. As the roast progresses, you can lower the airflow. This will allow you to roast a larger batch size with the same heater, the lower airflow will let you heater reach a higher temp.

BTW, very cool project.

Randy


Oh yes. Full on for the first few minutes and as the beans dry, they don't need nearly as much air flow.

I have three adjustments. Air flow, heater power and chimney damper. I don't think my heater is powerful enough, so if I drop too large of a charge, I wind up turning the airflow down very low near end of roast so I can get to 460F.

Tim
 
tra757
www.b757200.com/roaster/HeaterAirFlow.jpg

So this is a drawing of the air flow through my heating elements. Like I said earlier, I use two elements from the new air poppers you can find at Walmart for about $20. Those poppers are worthless for roasting, but pullout the elements, bypass the safety, drill a hole and they become reasonable elements for your DIY roaster.
 
allenb
Tim, you had mentioned you were getting too much resistance to air flow with the stacked donut style elements. They typically have an opening that can be enlarged substantially before running into the motor resistor nichrome coil. Not sure if you're using that coil or not. If not then you can increase the opening diameter even more. From what I remember, the main flow restriction is the small diameter 1.5" or so opening and not the perimeter area. The reason I mention this is that this style of element is very efficient and compact if you could make it work.

If you do go for a snip to gain some wattage I would enlarge these openings and you might end up with a great performing element without having to go through the time and hassle of creating a new design.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
tra757
The drawing is actually a design I did before I found the elements I am using. In the element I am using, I removed the motor resistor coil because I don't need it and it was in the way which allowed a larger hole in the center. While the design idea is a sound one, I think that the ones I am using are just too small to allow for enough airflow to lift much more than a 12 ounce charge. The design in the drawing is taller to allow for more air volume. I just need to order the wire and mica and build it up.
 
freshbeans
I kinda like that heat source. The MH-1 is a bit tall...hmmmmm. -Scott
 
tra757
freshbeans wrote:
I kinda like that heat source. The MH-1 is a bit tall...hmmmmm. -Scott


Yeah, totally. I think it is the most efficient method of heating high CFM in a compact space. I am pretty sure I could get more heat out of my double stack by cutting a few turns out of the element so it stays hotter. Not so many as to burn the thing out, but keep it glowing when the airflow is high. Maybe I will try that this evening......
 
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allenb
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Swap time! woohoo Don't delay in firing up those roasters! BBQ grill

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