Tiny cheap fluid bed roaster update: background roast test


Yesterday we tested the “background roast” feature of the free Artisan software, with Artisan activating and regulating the heater in order to let the BT cruise along the pre-designed profile. Before our test we made a few improvements to the hard- and software configuration.

Closing the air leak
Tije sealed the edge of the funnel to fix an air leak. This change boosted the power of the airflow into the bed of beans. Our first impression is that the maximum batch size increased from 200 grams to at least 225-250 grams.

Fighting spikes
In our last test drive we experienced a lot of spikes in the temperature readings. To fix this we installed two ferrite beads that were supposed to suppress the high frequency noise in the circuit. Marko Luther, also gave us suggestions how to get more stable readings. By increasing the filter values in the Artisan Device Assignment tab, we should get better usable readings. Marko indicated that a value from 80 until 90 percent should give us better results. These changes resulted in much more stable readings.


Improving Device and PID configuration

In our previous test we didn’t manage to let Artisan drive the PID drive the roast along the pre defined roast curve. After showing Marko Luther our configuration files, he quickly saw what caused the issue. The PID settings on the Arduino control tab had to be reconfiged. To make it work the source number needed to be changed into “2”. That’s the same as the BT channel number on the Device Assignment tab. Many thanks to Marko Luther for his great help!


Testing roasting along the pre defined roast curve

During the preparation of our test we saw chaff flying into the air pump. This chaff decreased the power of the airflow. Frans fixed this problem pragmatically by installing a little strainer on the air pump.

After making all of the changes we were ready for the ‘background roast’ test. The test was quite successful. We managed to get our prototype to roast along the pre defined roast curve. The graph shows that the PID follows the background. But in the image below that the precision can be improved. In graph below you can also see a big dip after the start of the first crack. This might have been caused by airflow changes during the roast.

background roast tc4

Next steps

More work needs to be done to optimise the PID configuration. Furthermore we are planning to put a kind of hood on the roasting chamber. This is supposed to improve the efficiency of the heating by restricting the loss of hot air. We are looking forward to do the next test run!


Frans Goddijn made (again) a nice movie of our test!

(movie by Frans Goddijn)

Tiny Fluid Bed Roaster update

(movie by Frans Goddijn)

Last week we updated the Arduino software of our air roaster prototype. Tije fixed the new safety switch that I brought along. In case of software failure, you want to switch off the heater and keep the blower active in order to cool the beans and prevent overheating of the blower and heating element. The switch bypasses the relays that are controlled by the Arduino control board. We also tried a new Artisan sketch that supports a “background roast” using the Artisan PID to follow a pre-designed roast profile. The background isn’t working yet in the video but with help of Marko Luther, who wrote the Artisan roast software, we have figured out the configuration. We are looking forward to do the next test run!

3D printed espresso dosing funnel


Recently I wrote about a 3D printable espresso dosing funnel that I designed. Yesterday the print of the design was finished. I wanted to have a fully functional prototype, therefore I chose to print it in ABS. That printing material (‘filament’) can withstand up to 100 degrees celcius.

The design is not final but I did some tests and I conclude that it’s already useful. It makes it easier to get an even distribution of coffee in the basket and prevents spillage of grounds. I have already some idea’s for improvement but if you want you can print it yourself!

Simple affordable-for-all fluid bed roaster

Tije design and construction of the roaster

Tije de Jong, Frans Goddijn and I are thinking of a small simple affordable-for-all fluid bed home roaster for coffee. The roaster is supposed to roast 200 grams of coffee and work with the Artisan roast software. Furthermore the machine is intended to have PID control and adjustable airflow. This combination of things would make it an ideal home or laboratory machine that will let you precisely execute predefined roast curves, roast different batch sizes and give consistent results. We decided to open source the design of this machine. This enables you to build this roaster yourself, contribute and help to further develop the machine.

Hardware and electronic design

Essentially the electronics for this design consist of a heating element, air pump, two relays and a temperature probe. The hardware design is inspired by the Roastuino project. In this project they used a simple heating element (heat gun), glass roast chamber and cheap (€ 12) but effective air pump. For the ‘electronic heart’ we used TC4 Digital Thermometer and Temperature Controller. The advantage of the TC4 is that it’s relatively cheap, programmable and it already has existing firmware to make it work with the Artisan roast software. After sourcing all the hardware, Tije manufactured the remaining parts and he also constructed the prototype (see Tije’s drawing above). We used a very helpful wiring diagram (use at your own risk) that we found on the TC4 site to connect the electronics.

Firmware for the TC4

Without firmware the TC4 will not do anything. Luckily there are different firmware versions (Artisan Arduino Sketches) for the TC4 available. First we tried the latest available aArtisan that we found on this TC4 site. The code was from 2013 and we somehow did not get it to work properly. On Github we found a more recent version (aArtisanQ_PID_6_0). After compiling the Arduino sketch made by Jim Gallt we got a warning ‘Low memory available, stability problems may occur’. Maybe the code needs to be optimised, but we just hoped it’s would not be a problem.

Testing the roaster

In the video below you can see our first test of the roaster.

Last week, we tested the roaster again. The airflow and heating are nicely balanced. When using 100% power from the heating element, we were able to get 200 grams of coffee in first crack after just 4 minutes and 45 seconds. That means that the machine has lots of power. The prototype was able to communicate with the Artisan roast software. We could log the temperature and set the heating percentage. The AC fan control however didn’t work. This problem was solved by installing the newer firmware .

Testing the airflow (fan control) after software update

Logging noise

Next steps

More work needs to be done. Priorities are to configure the PID temperature control and to reduce the logging noise. Many thanks to everyone that have made this project possible. To be continued!

List of parts

Below you can see the list of the parts that we have used until now. When you add up all the costs you can see how it somehow got a little more expensive than we had hoped.

Table: List of parts

Number Components Quantity Order Euro (ex shipping)
1 Fotek SSR 40 DA 1 Ebay 4.15
2 Crydom d2425-10 1 Ebay 25
3 AC zero cross detector 1 mlgp-llc.com 21.5
2 TC4 SHIELD 1 mlgp-llc.com 79
3 Silverchrest Air Pump 1 Ebay 12.9
4 Ceramic Heat gun element 30 Ohm 1 Aliexpress? 0
5 Laboratory heat resistant glass (90 mm x 2.5 mm x 200 mm) 1 Lgsbv.com 79
6 Funnel (inner diameter 97mm) 1 ? 7
7 Heat resistant kit (Uni Acryl AC 180) 1 Kachelmaterialenshop.nl 12.2
8 Jumper wires 1 Ebay 0
9 Tube mounting brackets 1 ? 0
10 Wood 1 ? 0
11 K-thermocouple (miniature) 1 tcdirect.nl 22
12 262.75


You can also read on Frans Goddijn’s blog about our roaster project.

Espresso dosing funnel design

Dosing the coffee in the espresso portafilter basket and distributing evenly can be difficult. A small funnel can help to ease this proces. Tije made a beautiful one for me and there are funnels on the market like the IDR dosing tool. I’ve recently learned how to draw in 3D and I thought it was a good exercise to made a first design. The prototype is not final and I haven’t tested it yet. You can however download and print the design yourself. Don’t forget that you will need to print it a bit larger (approx 1.5% for ABS) because filaments tend to shrink after printing. Let me know what you think about it.

La Marzocco Linea Mini, first shot

Frans Goddijn and I are reviewing the La Marzocco Linea Mini this week (to be published in an upcoming issue of KTC magazine) and here we extract a first espresso, using the double basket included with the machine, the heavy double spout portafilter, the LM tamper that comes with the machine. Also using the Acaia scales and a Compak grinder. Monitoring the group temp which is very stable around 83ºC after we set the extraction temp on 93ºC using a small mechanical wheel on the top left of the machine. The roast profile shown briefly during grinding is made by the free Artisan roast control & logging software supported and developed by Marko Luther.

This post was first published on kostverlorenvaart.nl.

Affordable fluid bed roaster

Tije de Jong, Frans Goddijn and I are thinking of a small simple affordable-for-all fluid bed home roaster for coffee. We use some hard- and software idea’s from the Roastuino project. Today we installed the electronics and tested several configurations. The results are promising. To be continued!

Sudden Coffee – Just add water and stir

sudden coffee instant

By Frans Goddijn & Jan van der Weel. This blog is also on kostverlorenvaart.nl

Travelling can be tough when you are used to excellent coffee. How does one prepare a decent cup on the road if there is no specialty coffee place in sight?

You can load all your equipment in your trunk but this isn’t a very practical solution when you travel by airplane or when you drive out to very remote places, if you want to go backpacking or if you don’t want to have another coffee related argument with your partner.

Now there might be a simple solution. A relatively new company, Sudden Coffee, promises to offer a solution. “Just add water & stir – it’s really that simple”, they say. Read More

‘Kitchen stress’ relieving coffee station

coffee station

I know that this coffee thing has got out of control. It has taken over our house. Our kitchen has become something of a laboratory. This 5 square meter space is crammed with cutlery, cooking equipment, kitchen appliances, dishwasher, washing machine, fridge, deep freeze, a vegetable stall and all of my coffee things: a giant roaster, a huge grinder, a big espresso machine and lots and lots of other coffee related stuff.

I have tried to convince my girlfriend that our kitchen situation was quite normal. This was everybody’s kitchen situation, I could hear myself say. However my words weren’t compelling and after some time I had to admit that she was right. Entering our kitchen gave me bad vibes. It was absolutely no relaxing feng shui environment. It was certainly the worst room in our house. Also, the space was not very practical. All the kitchen counters were filled with stuff. There was no more room left for cooking. That’s why I could regularly find my girlfriend on the kitchen floor, the only ‘open space’ left in the room. While cutting vegetables on the cold floor I ofter heard her mumbling ‘I hate this kitchen’. Read More

How to fix a La Marzocco GS3 pump on the cheap

Recently the pump of my LM GS3 espresso machine broke. It was the second time the machine experienced this problem in a period of one year. The problem was quite substantial. The pump refused to run after pushing the brewing button. This brought me in a depressing situation. I wasn’t able to brew any espresso.

The cause of the problem

What was the cause of this problem? Inspection showed that the vane in the fluid-o-tech pump head didn’t turn smoothly. That made it impossible for the motor to drive the pump head.

pump head rotary pump
Failing pump head la Marzocco GS3

Read More