This site created to document the feeding of my coffee addiction. My girlfriend introduced me to fresh roasted (at home) single source coffees and I’ve been spoiled by it ever since. Regular coffee has been forever ruined for me and now I need the good stuff.
As a result beginning April 14, 2010 I now have a Fresh Roast SR500. We started with a Fresh Roast Plus 8 and the SR500 and the SR300 were the replacement models for it. I’ve spent several months using the Plus 8 roasting coffee for us while visiting and I’ve admired the simplicity and of course the wonderful coffee. After getting the SR500 I began the process of figuring out how it works and how to improve upon it or at least track it. The blog will document some of the roasting and my thoughts on various equipment and beans.
Roasting Computers
One further obsession from all of this was triggered when I realized that the control mechanisms of most home roasters are horribly limiting. I had begun researching and created some electronic circuits in a simulator that effectively controls a simulated heater device and fan through a series of heat adjustments. In summer of 2010 I began working with physical microcontrollers as well as touch screens and other devices.
As time goes on I will continue purchasing various parts and build an automated roasting controller. At this time my intent is to allow simple control of roasting profiles with both heat and fan adjustments and providing feedback about current temperatures, desired temperatures, and how well those profiles are met by the controller. It will then estimate time remaining / time of completion. Once a roast is finished it will store the details to allow you to analyze each roast and attempt to let you recreate the roast at a later time.
It is my hope that I could eventually program the system to ask you certain details about your upcoming roast and beans and have the system suggest roasting profiles based on those answers and previous preferences. Ultimately if this works out well the system should be able to be adapted quickly to most any roaster.
About SteveS
I have been involved with technology for more than two-thirds of my life first learning to program computers when I was in 4th grade. Since then I’ve learned programming in various web technologies such as PHP, ASP, and Javascript, as well as other languages like C, Cobol, RPG, and database technologies like MS-SQL, MySQL, and more. Professionally I have worked in and ran IT departments for Federal Government, Veterans, Telecom, Hotel/Lodging, Manufacturing, Engineering, Aerospace, and Banking industry companies. For nearly 20 years I have worked in IT with small locally based 40+ employee companies through 6000+ employee companies overseeing IT functions operating in hundreds of offices spread through 70+ countries.
In addition to my addiction to coffee I do a lot of gourmet cooking, and photography. For fun I (try to) play guitar (I own 6 guitars), am trying to learn piano, and I run several websites about aquariums.
Hey Steve, first of, let me say I went through and read your posts. Great work, and I love the detail you put into your blog. Curious if you have any updates.
I have a SR500 that I bought many years ago, but have not used in a long time. I recently began using it again, and my first roast was great. However I think I may have overheated my machine on the second roast that week. ( I only had about 60g of beans ) and so I ran high with low fans to try to maintain temps.
The machine began forced high fans regardless of fan setting.
Since that day even on high fan low heat, after around a min I hear the fan turn on high. All my batches come out very spotty and takes a very long time to first crack. This makes me suspect that its also turning down the heat.
Now I know that there are several fuses/safety checks, but do you have any thoughts to begginer trouble shooting? I would like to try a tempeture probe, but not sure what the easiest probe to use would be.
Hi Steve, I have a FR500 that died last week. It powers up and lets me change the roast time, but when I press the run button nothing happens; no heat, no fan. I tore it down and checked some of the obvious things like the rectifier, the bimetallic, the thermal fuse, etc… but I can”t find the bad component. Do you have any ideas, or could you point me in the right troubleshooting direction?
TIA . Tim
Not really sure what to offer here. The fuses and other items can’t easily be tested without disconnecting the main circuit board from the rest of the system and even still I believe some of it has to be desoldered to be tested. Once I dismantled everything on mine it is easily testable but only because each section works independently and I monitor temperature and other things to confirm the fan is running etc. On the stock 500 the fan runs off of one of the two heat coils which is why it takes longer to cool and still spews hot air while in “cool” mode. The fuse inside the heat coil area is designed to blow once and then it must be replaced. Since it is using a sort of “donut” ring crimped through the backer to hold it replacing that will takes some “engineering” but there are examples of what people have done with their poppery units. There is one on the circuit board that should be visually inspectable.
I’m not sure what you mean by “Run” button since that is a new appearance on the SR700. The 500 uses the slider switch to go from Off to one of the heat levels. Then it has a cool button to trigger programming to cool and then shutdown. The switch, buttons, and the fan knob connect the the Atmel chip on the board so they are lower voltage functions. They trigger the other parts to turn on through output “trigger wires” on the Atmel chip which is programmed to roast coffee and the outputs lead to other circuits that pulse the power to the fan or trigger the heat to turn on so it is possible that chip fried but I wouldnt consider that very likely.
It is possible the slider switch has gone bad or that the up/down / cool buttons are “stuck” either literally or due to a failure of the material. Any pressing of the bubble button items will interrupt the normal function of the roaster so if one is stuck then it won’t do anything until it unsticks.
Hi Steve, thanks for the quick reply. I would imagine that the thermal fuse would be open if it had blown – even in-circuit. It still reads zero ohms… I used to work for a board house and we had to hand solder those bad boys without blowing them. (used copper alligator clips as sinks). I think I’ve X-rayed hundreds of them…. 🙂
I did have all the boards disconnected, i.e. a total tear down specifically to help isolate any issues. I could read the diode drops across the rectifier diodes on the fan module for example.
Since i get a display and I can bump the time up or down, and see it change, I’m guessing the Atmel chip is fine. Also I measured 5VDC on the logic board.
The dome switches are ok two. None of the are stuck in the on position (again had a lot of experience with those).
I really haven’t studied the power wiring in detail like you have. I’m wondering if it isn’t one of the rectifiers used on the power board for the fan and heater?
My unit has a run/cool button. My slider goes from cool to low to med to high… …so if the logic board is working, and the atmel chip is telling the fan and heater to start, where does that signal go?
I don’t know how much time I want to put into it… Any recommendations on how to power the fan to see if it is working?
Now I’m thinking hmmm. slider switch. If it is stuck on cool, nothing would happen when the run button is pushed. Should be easy enough to check – even if I have to desolder it…
I’m currently working on a DIY project that requires 4 directional buttons and a select. I originally etched my own Button Pad PCB and placed the buttons on them in the same configuration you have but they were unreliable and over repeated pushing they broke off. I was wondering if you could share which buttons you used and any suggestions you have for creating a more stable button layout…maybe I can even buy that button layout pad you have. Thanks for the help!
Best,
Sam
I’m not sure what you mean by them breaking off. I’m assuming you mean that the soldered connection snapped off of the board. If you’re using surface mount switches you might want to switch to through hole for buttons that get used a lot. Through hole is pretty sturdy as long as the buttons are snug against the board when you solder them in place.
I encountered an issue with the circuit design on the last switch and since I moved to a new house right after I was testing it and was remodeling the old house for most of the time since I last posted on here I haven’t had much time to work on fixing it. It worked when it was in a breadboard prototype but stopped once I had the PCB made. I’m thinking one of the resistors was calculated wrong and the breadboard didn’t show the problem. I’ll be getting back to the coffee roaster soon and had been planning on testing a modification to the PCB in the next few weeks before I send off a revised board.
The buttons I was using are made by a company called MEC. I found the buttons at DigiKey. They’re designed for commercial purpose projects with LOTS of pressing. The ones I used are actually illuminated from behind with a LED inside the button but there are cheaper ones without the LED. The way these work you pick a button and then a cap for the button. Different caps have different possible buttons for underneath. Some of the buttons are pre-printed with text on them or symbols while others have various shapes.
If you lookup MEC tactile switches on DigiKey and review the datasheets / product catalogs there and/or at MEC you will eventually find some catalogs that show which ones go together and some of the possible options. They truly are very robust switches.
Another possible issue for the strength of your buttons is your PCB. The PCBs I used were made by “OSH Park” which have very sturdy quality boards. The traces don’t peel off since they’re commercially produced (but inexpensive) boards while your own etched boards might not hold up as well. The painted on mask helps stabilize the board too so a lot of homemade boards are good for quick tests but not for long term use.