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renatoa wrote:

I see no functional disadvantage for exhaust, just aesthetics, for my eyes, too much tubing.

In the lower area, I am curious to hear how much presure is lost by the 90 degrees pipe turning just below the perforated plate.
What about an asymmetric design? they are so rare... and I like them more than centered fountains.
I mean an 135 degrees turn instead 90 degrees, and air entrance lateral shifted from the center.

CK wrote:

Nice photorealistic rendering. Are those your own CAD parts rendered, or do you download generic files from an open database?

I kind of like the shine and muscle of the SS pipes.

cdrake39 wrote:

Well, after some contemplation (and convincing from another user - thanks jbrux4!) I decided to use tri clamp fittings in my design. The primary reasons for this change are ease of cleaning, modular setup which allows for easier upgrades in the future, and aesthetics. The photo shows the concept for this design. Lots of design details to work out, but I'll have a better idea of how to tackle them when the parts arrive. I'm hoping to permanently affix a mesh gasket to the bottom of the 4" sight glass so I can remove that section (without having beans fall everywhere) to remove the beans when roasted.

dstedman wrote:



Would you eventually want to make a list of the parts you're using for future builders? Could be helpful - I'm having trouble finding the stainless steel parts that make up your tubing and the base of your roast chamber!

cdrake39 wrote:

Hey everyone - just working on the roaster wiring and had a question about thermal fuses.
A) I understand it is a safety feature, but I've seen some threads where people have removed the fuse and modded the thermostat to get extra heat from the element. Is this actually necessary?
B) The heat element (removed from a heat gun) did not have a thermal fuse. How do I go about sizing the correct thermal fuse? I would rather not size it too low and have it burn out before even reaching roast temps, but at the same time would want to size it appropriately so the element doesn't burn out
C) How does one install the thermal fuse? I assume solder is out due to the temps. Do you just loop it around the riveted connections on the heat element? (see pic)

CK wrote:



The top right and the bottom left image seem to show your heater's safety shut off switch. If it is similar to the ones I've worked with, there will be a tiny piece of metal under the copper contact bridge. If the air gets too hot around the element, the temperature sensitive tiny metal piece deforms breaking the electrical connection for the heater. As it cools it resets to its original position and the element is still intact. If this safety is removed with tweezers the electrical connection will permit higher temps at the risk of burning out your element or setting fire to your machine... it will not switch off for a high temperature condition with the safety bypassed.

renatoa wrote:

The reseatable fuse is 180 C, to avoid popcorn burn, it is actively working on-off during popcorn normal operation. This is the fuse that must bypass for roasting coffee, because 180 C is too low for FC and development.
The other is a normal fuse, one time permanent melting at 250-300C, for safety against home fire. Never heard someone tripped during coffee roasting.
You would need a mix of both, a reseatable fuse having the safety fuse range.

renatoa wrote:

Too low, imo... I hope is a typo and it is 272 C
In my setup the environment temperature, i.e. the air in proximity of beans, is frequently bigger than 250 C.
Another example more related to a hotgun style, the Gene exhaust air at glass cylinder inlet is 300-330C for a standard mains voltage, varying wildly with mains.

greencardigan wrote:

Yes CONFIG_PWM is correct.

Yes, the HTR_CUTOFF_FAN_VAL should work in all modes.

The value you choose for HTR_CUTOFF_FAN_VAL will be dependent on your specific roaster. You should have it set to a fan value that will allow enough airflow through your heater to stop it overheating. I have mine set about 10% lower than the lowest fan value I need during a roast.

I recommend doing some initial testing without the greater connected so you can confirm everything is working correctly.

renatoa wrote:

Mains ground.
Surely not to electronics ground !

renatoa wrote:

I thought you mean the sheath of the element, it definitely needs to be grounded.
There could be a lot of (conductive) things that could enter in the element and short the wire to the tin wall around ceramics... a carbonised bean fragment being the most common scenario.