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500g (hopefully) fluidbed roaster
This forum helped me a lot with my build so I thought Iīd share it and maybe save someone a few headaches.

I have started the project in summer and thought it would be a quick job. But boy, was I wrong. Following probably the most basic fluidbed build I ordered a 2000W heatgun, SS shaker and an air-matress electric pump. I put it all together thinking I will be roasting in no time. Tested it and to my huge frustration found out, the small pump wonīt move (let alone loft) even a single shot worth of beans.

I wanted it to be a cheap, apartment-friendly build, so i couldnīt buy huge vacuum/spa motor and try to make it work. So my second try was a leaf blower, that looked promising and had enough power to move some beans directly, but when I forced the air through the heating element section and the dispersion plate, it lost its oomph and I was back to square one.

After the second attempt I laid the project to rest for a while and tried to find out what would be the best way (cheap and easy to build) to solve the blower issue. It looked like I will have to buy vacuum cleaner motor - at first I was looking just at the motors but then I decided it might be best to just buy a suitable cheap vacuum cleaner and just go with that. And then I found what I think is a fluidbed jackpot - fireplace vacuum cleaner. I didnīt even know such thing exists and it popped up because they are so darn cheap. But it seemed to have all the features I was looking for:

1) Itīs cheap - mine was about $30
2) Itīs strong enough - most of them are rated at about 15-16 kPa (60"H2O)
3) Itīs easy to use the air outlet - on most of them you can use both inlet and outlet with the hose so you can use them as a vacuum cleaner and to start the fire
4) They have an ideal design - most of them have the air outlet pointing straight up and the body is just a metal bucket

And they even have some great features I didnīt even hope for:
5) They are made to suck hot/warm ashes and mine is rated to 40°C, so there is room for future recycling upgrade
6) Once Iīm done, I can disassemble the top part and store it in the metal bucket so it doesnīt take up much space

Only downsides are noise (think loud vacuum cleaner) and lack of control (itīs just ON/OFF) but other than that it works great. And since I plan to use TC4 to control it in the future, I donīt miss the regulation that much.

First test was (kind of) a success - I put in about 250g of roasted beans just to see where Iīm at and when it blew the coffee all over my living room, I deemed it "strong enough". Next phase were Adzouki beans, that are quite heavier so they stayed in the RC. I even tried a complete "roast" with them and was quite happy with the results.

I was trying to follow some basic profile:
130°C in 2:00
160°C in 5:00
175°C in 7:30
190°C in 9:30
202°C in 11:30
Cooling in RC from 202°C got me 100°C in 1:30 and under 60°C in 3:00.
There was still plenty room to roast faster and cooling could be better if I used cold air from outside via a hose.
I wonīt know until I try, but I think the setup should be easily capable of loads yielding 250g of roasted coffee which is my usual weekly consumption. And when I tune it (air-leaks, heating chamber, roast chamber, recirculation) it should handle 500g of green coffee. At the moment the most limiting factor is the roast chamber - it is the body from the shaker which is not ideal. I am planning on using a chopped Simax french-press carafe.

Attached is a quick shot of the contraption. Still a WIP version.
RedAce attached the following image:
I will be interested to see how well you can seal the vacuum canister. I used one on a build a few years ago. It is optimized for vacuum but not for blowing. So it will take more work to get it sealed. I do like your blower choice. It sounds promising.
Bad coffee prevails when good coffee roasters stand by and do nothing.
Love the creativity, make sure to update!
The canister is not an issue at all. I could actually use just the lid as a standalone unit. The container is just for vacuuming. There are minor leaks around the motor housing on the lid, but they could be easily sealed with some silicone. But the unit has way more power than I need at the moment and I rather have some minor leaks on the output end than having to limit the air intake and strain the motor (which I have to anyway).
Biggest issue right now is the RC - I have to get a diamond dremmel cutting wheel, chop the Simax carafe and hope it will work properly.
Then it is some kind of control unit - right now I can switch the heating element between 1000W and 2000W and limit the blower intake. This worked fine for the test roast but eventually I want to go the TC4/Artisan route. Considering a ramp/soak PID as a temporary cheaper solution since getting the TC4 to Czech Republic is not easy nor cheap.
The base is an Arduino, those should be available in the EU.
The Arduino world is a complete mystery to me. As far as the hardware goes, I am quite capable and should be able to put it together. But the software part scares me...

Roaster update - I really didnīt like the jet engine noise it was making, so I ripped my DIY preinfusion module (which is just a triac speed controller) from my Gaggia and used it for the blower. Works great and I should be able to hear the FC now.

Diamond cutting wheel and green coffee should be ariving tomorrow so I might actualy roast my first test batch this week.

Another good thing about the vacuum cleaner is the hose - I can roast on the balcony, not worry about the chaff, noise and heat, but still use the warm air from the living room :-)

In the long run, I would love to use an electronic 4-way valve to mix the cold air with hot output air to get a stable 40°C (which is what the vacuum is rated for) and have a stable environment independent on the ambient temps.
Good job! It sounds like you are off to a good start, and you are after my own heart about keeping a constant temperature for the supply air.
Don't bother about control of the roast temperature too much. I simply set a percent output based on the ambient temperature and keep that temperature throughout the roast. The 'natural' curve of a fluid-bed roaster plus the blower speed control is enough control for me, and I am retired control engineer with a PLC stuffed in the garage someplace'
Also I maintain a constant 52C - 65C at the blower inlet by mixing the roast chamber air with the ambient air. My average load is 420-500 grams and I usually roast with a setting less than 1500 watts. Note: it will be about 1500 watts today because it's cold out in the garage.
Edited by oldgearhead on 12/13/2016 8:05 AM
No oil on my beans...
....almost forgot. I use an old PID controller with a percent output control,so that, the temperature of the batch is also displayed...
No oil on my beans...
The sketch language is easy to use, and there are a lot of examples on line. Btw the language and dev environment is free
I know the language and environment are free, but I need the TC4 and I thought I would have to buy the TC4C module since I know nothing about Arduino. The board, ZCD, crazy shipping, tax and customs would add up to $250. Which is madness. Especially if I consider, that I managed to put the roaster itself together for way less then $100. Right now I decided to go with two dimmers to control the fan and heating element manually, get a cheap Arduino UNO, learn a bit about it and then order just the TC4 Shield kit. With some creative shipping it should get the price to an acceptable level.

Roaster question - there is a small gap between the shaker top and the Simax RC. What is the best way to seal it, considering the high temperatures? I tried "gaskets" made out of crumpled aluminium foil or a baking twine. Both seal the gap quite well and both should withstand the heat. Any other suggestions?
I use red, high temp, silicone 'O' rings. But yours are probably fine..
No oil on my beans...
First "hot" roast done. Very happy with the results. 200g of Brasil Santos beans roasted to 210°C in about 11 minutes. Could go way faster (even in the freezing temperatures) but tried to follow the chosen profile through airflow regulation.

Good news is that the roaster works fine. Even better is the fact that the 500g loads I hoped for in the thread name should be no problem. The blower handled test batch of 500g beautifully at about 70% power and the heating should be able to keep up with that.
Bad news is I couldīt hear the FC and I donīt actually know how to fix that. Maybe try to soundproof the vaccum cleaner somehow. So I had to eyeball it by the bean color and BT.

Couldnīt help myself and already prepared an Aeropress which tastes surprisingly good considering itīs the cheapest coffee I could find just minutes post (pretty dark) roast.

Balcony is covered in chaff, it is freezing outside but I am a happy camper :-)
RedAce attached the following image:
Looks like a pretty even roast at about City +, but lighting could be deceiving. Congratulations!


RedAce wrote:

First "hot" roast done. Very happy with the results. 200g of Brasil Santos beans roasted to 210°C in about 11 minutes. Could go way faster (even in the freezing temperatures) but tried to follow the chosen profile through airflow regulation.

Good news is that the roaster works fine. Even better is the fact that the 500g loads I hoped for in the thread name should be no problem. The blower handled test batch of 500g beautifully at about 70% power and the heating should be able to keep up with that.
Bad news is I couldīt hear the FC and I donīt actually know how to fix that. Maybe try to soundproof the vaccum cleaner somehow. So I had to eyeball it by the bean color and BT.

Couldnīt help myself and already prepared an Aeropress which tastes surprisingly good considering itīs the cheapest coffee I could find just minutes post (pretty dark) roast.

Balcony is covered in chaff, it is freezing outside but I am a happy camper :-)

Was your vacuum too loud or did you possibly reach 1c too slowly? 210c or 410f in 11 minutes isn't exactly slow but I have found that if I am too easy on the beans prior to 1C I often don't hear much if anything for 1C.

After several 100K of pistol, rifle and shotgun blast over the years from shooting, my hearing is not that great. When I'm roasting Brazilian beans, I can't hear the FC in them.
I just reduced the size of my roast chamber from 5.3" diameter to taller 4" diameter to get better bean movement and my roaster is a bit on the noisy side. I first roasted some Columbian after making this change and could hear the snaps of FC rather well, something I've not been able to do before. However after two roast with the Columbian, I roasted some Brazilian and never heard a single snap of the FC and have never heard the FC of a Brazilian bean. After one roast of Brazilian, I roasted a Guatemalan and could hear the FC in those.
I just don't think the Brazilian beans make as hard of a FC as a lot of other beans and with a noisy roaster, along with bad hearing, it makes them very hard to hear.
Also, on the roaster modification, I wish I had done that years ago. I have never been real happy with the quality of some of my roast, and especially on certain beans. I finally concluded I was not getting a uniform rotation of beans. Some moved rather quickly, some moved slower. Going to the smaller 4" chamber and opening the bottom screen another 5/8" wider, I now get very good, consistent movement and I've immediately noticed a big improvement in the uniformity of the roast and the flavor.
I did almost create another problem though. Opening the screen is letting more air though, for the first time when roasting below 40 degrees in my garage, I've seen my heater hitting 100% once the beans get to over 400 degrees. I was able to overcome this by programming the blower speed to reduce to 75% at 400 and the beans have lost enough weight they still move fine. I'm already running a 2400 watt heater on a 20 amp, 120VAC circuit so with the fan running also, I don't have much room to go up more without converting to 240. Which I can do if forced to, but hopefully, I won't be doing many roast while freezing my butt off in the garage.
The roast looks more like a Full City - the light makes it look a bit lighter. I stopped the second roast a bit sooner and got really nice uniform City+ roast. Even better is the fact that both my wife and friends that came over today absolutely loved the cappucinos made from it. And I like it as well even though Iīm more into lightly roasted 3rd wave coffee with more pronounced acidity and fruitiness.

Two disasters happened during the second roast. The dimmer stopped working (maybe too big load for it, even though it was rated at 600W - same as the blower) so I am back to air intake regulation for a while. And the RC cracked - after the first roast I glued the glass portion to the shaker and even though I tried to leave some room for the expansion of the metal it was not enough. Thankfully the glass held in one piece, I was able to finish the roast and strenghten the glass with strips of fabric and heat resistant glue. Should be fine for some time.
Coming back after some time with a few updates and a question.

Roaster is working great, I upgraded the system with dimmers for airflow/heat control, a TC4 for temp measurement/logging and a chaff collector. I usually do 350g batches as I like to experiment with blending and donÂīt use that much coffee. But 500g batches should be no problem so I consider the project a success (but still a lot of work to be done - typical case of a DIY project in a permanent WIP state).

One huge issue is the temp measurement - there comes a moment in every roast where the temp reading (both ET and BT) jumps up like crazy. It comes at a similar time and temp every time as I am approaching the end of drying phase (around 120°C). I am pretty sure, that my temp readings are good, considering FC comes around 190°C and roast are done between 200-205°C so I consider it a measuring fault/artifact. Good thing is that the important roasting milestones (DE and FC) are not affected by this that much but it still drives me crazy. It makes any profiling pretty much impossible, the same goes for a PID control I planned to implement. Has anyone encountered similar behaviour or know the cause of that? And most important - how do I remedy that?

I tried several probes, all calibrated with boiling water, all behaved the same. My guess is that the reading in the first part of the roast is somehow influenced by the humidity escaping the beans but I have never seen this behaviour in other fluidbed roasters and mine is no different from them? Also I would not expect such a significant impact on the reading from the humidity in a Fluidbed roaster. Even the dip in temp during FC that is normal in drum roasters doesnÂīt happen for me. And the ET behaves the same even if the probe is UNDER the roast chaber and the humidity shouldÂīd get there at all.

Attached is a typical roast - beans look and taste great but the graph is just weird... Thans for any input.
RedAce attached the following image:
From looking at the ET and BT plots, I don't think there can be any possibility of it being measurement errors nor can it be from RH changes in the beans. RH from the beans will not change abruptly during that phase of the roast. Are you certain that the voltage to the heating element is not changing at that time?

A 160 to 230 C swing in ET along with a corresponding rate of rise increase in BT at the same time pretty much proves (to me) you're dealing with a change in power level.

1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
I doubt that a power change has such instant effect...
After TP the ET in my oven can't raise more rapidly than 80C / minute... and when I cut power in final stage of development, the drop is about 1 degree every 5-10 seconds.
DIY: TO based IR 750g
Moded commercial: Dieckmann RoestMeister, Nesco, popper(s).
TC4ESP, MS6514, USB/Artisan/Apps, PID controllers
Grinder: MBK Feldgrind, mod'ed Porlex to 47 conical burrs, vintage PeDe Dienes, Kinu M38
Gaggia Mini, Aeropress, drip
At first I thought the same - the first suspect was the dimmer. I thought, that as I was slowly increasing the power during the roast, the potenciometer gave some weird signal to the heating element turning it on full whack. But it happens every time at almost the same BT and even if I donÂīt touch the controller at all. So I donÂīt think it is a power issue. Jump in the outlet voltage is also unlikely - how would I get the same spike in voltage every single time at the same spot? I am not even sure my roaster is capable of such rise - it is usually at about 60% at this stage of the roast and I would not get such spike if I turned it all the way to 100%

Today I roasted another batch of Panama beans and it is the same story again. I even put another probe in (from a standalone thermometer) to check my measurements and it spiked at the same.

I can try to "roast" some navy beans or something similar - if it is related to some humidity escaping from the green coffee it should not happen with dry beans...
RedAce attached the following image:
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