Let me tell you about the time….

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So I’ve ordered a plethora of stuff lately. Yesterday the 5×7 magnifier came. I’m figuring out I have no place to work on this stuff properly so it’s sort of wedged on my desk, and then today a box from Mouser showed up. In it I’ve determined I purchased the wrong AC adapter…. so now I need to order another one but this is for a slightly later stage so it can wait a little. Plus I believe I have a power supply I used on a fan to keep the air moving in my indoor orchid tray and lights area that is not being used currently due to a different setup that I’ve already stripped the ends off that I could then use with the relay board I received from Bulgaria. I’ll probably find something else to use that power supply for later anyway.

Anyway, TODAY the Mouser box arrived. In it were a variety of 0603 sized capacitors. For those that don’t know what that means… they are .06 inches by .03 inches or approximately 1.5mm by .77mm give or take a few hundredths of a milimeter.

Today I learned that fluxes are awesome when soldering SMT devices. I managed to mount my 32.768 6pF crystal and some of the 11pF 0603 capacitors from the selection but it was an adventure. I’ve lost approximately 4-5 of them into the rug somewhere now. Two are now securely attached to the board. I got the first one out ok but lost the second one immediately. I got a third one out but it didnt make it to the table and went straight for the rug. I recovered one of them from the rug and then tried to get it soldered onto the board. Two of them blew away using the hot air system. Once I got a corner tacked down properly it went much smoother. After allowing things to cool off I mounted the USB II Microchip board back into the IO board and connected to my LCD and fired it up. Immediately the clock on the display started ticking off seconds.

I had quite a bit of difficulty getting the soldering stuff going. I looked up temperatures for things on Wikipedia and ended up grossly under heating things up. I ended up looking up the soldering station’s manual on the internet since I couldn’t actually find it right now due to the bags and bags and boxes of parts and shipping materials everywhere. Once I finished looking that over things melted much more easily and started acting more normally. Once I started packing the parts away into boxes I discovered the real manual buried in the pile.

As mentioned the timer is running just fine. I am waiting a few hours to see how far off the time is from my computer to get an idea of whether this has a slight or a significant drift. So far it looks quite good. Time will have to tell. ULTIMATELY being REASONABLY close over a few minutes is fine. In the final project I will be using a DS3232 I think it is as a time source to populate the microchip “RTCC” after powering the system down and then turning it back on. Microchip for whatever reason built a system that has marketing towards it having a Real Time Clock built in. The problem is it doesn’t keep time when you turn it off due to having no backup battery of any kind. As a result it needs to be set every time you apply power to the system and then take it away when you turn it off.

Since I intend to hook this to the internet / router eventually I will try to implement a NTP client to set time into the DS3232 and then from there into the Microchip PIC32 while it runs. I’ve now manually adjusted the clock to be in sync (visibly anyway) with an atomic clock synced clock I have here immediately next to it. I set it at 10:12 so I will check it again in a few hours. The longer it seems stable the less I’ll have to make it lookup from the Dallas chip…..

I believe tomorrow I will be getting some ambient temperature, humidity, and barometric pressure sensors as well as a few other sensors I may or may not be experimenting around with too in this and other projects. So far 10 minutes in the clocks still seem synced so we’ll see what happens over the next few hours and overnight.

Oh… and Microchip never replied to my “technical support” request to get an idea what they suggested. I think the details I’ve found on the internet meant several different options of crystal and capacitor combo were ok and what they DESIGNED it with was not very common to find. I managed to find what it sounded like it was designed for though and so far so good.

I should start mounting the header pins this weekend and start hooking things to some of the external sensors to start getting readings into the programming. Once that happens I can start porting my PIC24 code over making a few adjustments and then start programming the roast curve tracking portion.

More ordering

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I have now ordered a series of parts from Mouser. This includes some lead free solder (ouch that stuff is expensive), flux, several different crystal oscillators and what I THINK to be matching capacitors, as well as a ton of headers for jumper cables. I entered a ticket for Microchip more than a week ago and have received no response whatsoever from them regarding the oscillator. Reading the instructions there was no mention of a type of crystal to use beyond 32khz. They mentioned 11pF capacitors of 0603 size. From what I can understand it SOUNDS LIKE in a properly designed board if you have a 6 or 7pF crystal you install an 11 to 14pF capacitor when it has short runs for the wiring etc. HOWEVER yesterday I found on the ethernet board they explicitly defined the crystal as a 12.5pF crystal. In my observations it appears that if you use 12.5pF crystals you should use 22-27pF capacitors, though.

The unfortunate problem is some people report using 11/12 capacitors with 12pF crystals and other report needing to use 27 etc. I’m thinking it MAY depend on the manufacturer of the crystal as to how sensitive it is and needing more or less power from the caps to be held up to trigger the oscillations of the crystals in addition to the variables of the individuals circuit layout. In other words some times it works no matter what and others it does not.

I still need to get some solder paste in addition to the rolled wire solder. I had issues identifying this on the Mouser website in the search except for a couple versions that had more than five tubes as a minimum. I do not have need for / ability to consume more than one syringe/tube right now so I need to find a vendor to procure some from that does one at a time. I stumbled across one a few nights ago that sells one at a time but I’ve not had time to dig through the browser history to find my way back there yet.

Once I have the solder paste and after the parts arrive mid week I can solder in the crystal and caps to see if they work for the timing functions and continue my efforts at programming the interface. Most of my programming is going to wrap around being able to gauge time changes happening so I need to wait for that to happen.

Currently I have a thermocouple breakout board that I will be attaching to some of the IO lines. I also have on order a relay board that has not arrived. Once the relay board arrives I can attach it to the development board and configure it to turn on the fan when the program run starts and not to turn it off until after the heat drops to a safe level. The heat will trigger on and off to maintain the desired ramp at this time. I will eventually replace it with a variable “dimmer” once I work out the other kinks in the system to give it finer control.

Early July Update. Observation on SR500.

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Having been offered full time employment starting the middle of July after approximately 2 years of unemployment things are looking good for getting some progress on this project. LOL! While this may sound odd this is actually good due to the fact that I’m building (if all goes properly) a somewhat professional-esque coffee roasting computer. It takes a lot of money and resources to design this thing. I’m already into the project around $300-400 worth of circuit development kit gear and need a lot more stuff. In the end I’ll have a complete system that will be significantly cheaper to build but still have all the development kits to make other projects. I chose that route because of the “other projects” for down the road instead of only buying the things I need right now. While having full time employment will limit my available time it DOES however allow me money to keep purchasing all the parts.

Most projects you find on the internet for a coffee roaster use something like a Basic Stamp or some other very limited processor. It also usually involves hooking together a few things someone finds off eBay hooked together with some various wires and connectors salvaged off some old computer equipment and other devices abandoned in the garage. By the time it’s done you get a picture on the internet of some “finished” popcorn popper that looks like it’s about 30 seconds from taking out a corner of your house into a huge crater or like it’s some sort of industrial wiring project of conduit and electrical boxes.

I’m intending on making this thing as small as I can make it and sealing it up inside a electronics case with a single cord or perhaps a cord and a sensor wire that plugs into the back of the case that leads to the roaster. I don’t want 50 million little cords and sensors and clunky switches and other doo-dads spread across my counter. I also want to be able to pick the whole thing up and move it somewhere else without accidentally cracking off a wire and needing to re-solder it. I don’t know about you but I love my coffee. I don’t love having to re-solder the wiring just to roast some more or being unable to use my kitchen for anything else.

My Kitchen is not that big. It cannot accommodate a lot of “stuff” strewn around it. so the entire thing will need to be compact. As a result I intend on having a case that has a LCD touch screen installed. It will probably have a LED or two and at most probably a single power switch on the front edge or side. I will likely try to design the circuitry so that it fits onto one or more circuit boards stacked on top of one another. The LCD will be mounted on top with various connectors and other items stacked below it. I’m reasonably sure I can shrink the majority of this down into a space about 4″ by 6″ and about 1.5 to 2″ tall.

As mentioned I recently purchased the PIC32 development gear. At the moment I’ve been working on the GUI. This is a lot more complicated programming than I’m used to. Additionally I’m having a few “weird” situations where LED’s on the starter kit are lit that I don’t seem to understand why. When I turn on an LED that is normally off things work fine but then when I programmatically turn that one off the LCD turns off too though they shouldn’t be connected at all. The other LED works fine turning it on and off the same way. One of these LEDs simply stays on all the time no matter what.

At the moment I now have a “splash screen” functioning. I touch the screen and it continues to a “Home” menu. From there it offers several buttons to run the manual or the automatic roasting menu. There is also a provision for a Setup menu. I am still waiting for the ethernet to arrive that will allow me to download roasting data out of the system or pre-configure a roast from a web page. It currently draws temperature onto the screen from some “made up numbers” I have the thermocouple and the chip that will convert the sensor reading to numbers but need to solder it to a board that I can connect to the processor. I also need to do the same with the clock chip that I have as well. The processor has built in clock routines but they only work while the system is turned on. As soon as you cut power that clock loses it’s data. As a result I will program the system to read the clock chip every time the system turns on.

Over the next few days I will program the roasting screens to change certain display areas based on the simulated temperature numbers and then integrate the “control” portion where it then stops the increase in temperature and then tries to increase it appropriately. I still need to figure out the timer stuff… it doesnt seem to run on the demo and I was thinking it had to do with an oscillator being missing but this seems to be related to USB stuff in the documentation for the starter kit. This doesnt seem right though. I need to figure that out and then the next step is to start ordering all the pin headers and not included on some of the other boards. I’ll try to figure out a few more of the parts that I’ll need and order those in the next few days as well so I can keep working on this. Assuming I’m right that the crystal is required apparently Microchip decided to save 83 cents by not including the oscillator.

Also as a side note. Due to the job offer I completed a move to Northern California from Central California which has kept me from messing with the coffee much until now. A variety of coffee that I roasted here with the Fresh Roast +8 took approximately 6 minutes to hit second crack. Using a SR500 where I used to live took about 6 minutes as well while running the fan at half speed for the first two minutes. To do the same thing here with the SR500 appears to take around 7-8 minutes with a lot more slowing down the fan to around the 25% setting once movement starts to flow more easily and first crack was reached.

Pic32 Starter Kit USB 2

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As mentioned there was a problem getting the main “brain” for the development kit. It was on “backorder” to June 28th and supposed to arrive on the 30th. While watching the website I saw the date slowly tick longer day by day. Eventually I got an email that said the date was going to change. It claimed the new delivery date was going to be July 30th to ship. I watched the date and it continued to tick forward only one day at a time even though they told me via email that it was due on the 30th of July to ship. I wrote an email complaining. They indicate on the website that they will respond to questions (I was seeking a ship date clarification due to the website saying one thing and the email yet another) within 24 business hours. Assuming they have 8 hour days this would be 3 business days. No response came so I watched the live sales chat which showed for almost a week with nobody available.

Finally one day there was a person online and I asked them. They said that their scheduling people said that the 30th was the best date they had and agreed that the info on the website was problematic that it didnt agree with what I was being told and would mention it to a manager. I seriously doubt that ever occurred but whatever.

I’m currently moving and the day I got unloaded a notice came in the email about a change of status on the Starter Kit. It indicated that the order had been shipped on the 30th. The package is due to arrive today according to FedEx. This leaves the ethernet circuit board to ship. It claimed the same 30th of July delivery date in a previous email so who knows when that will arrive. The website continues to click forward day by day not matching what I was told.

I still need to finish setting up the office area where I will be programming the development kit from so it will be a few days before I start work on the user interface.

Parts received some not…

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As mentioned some of the items had later ship dates than others. As of June 16th I have received the IO board, the prototype boards, the LCD graphics w/LCD kit, and a power supply.

In addition to the development kit I have on order a few engineering samples for a few parts to test out before I pick vendors to program things based on and start purchasing real parts. These engineering samples will be mounted on “prototyping” boards that will either be custom built or ordered off the internet pre-made. Occasionally chips are used in a variety of ways so I will simply build a board to solder them down to and install pin headers to attach to on the board. These will also serve as “test” printed circuit boards as I learn to make boards on my own.

The ones I have received so far are a chip that has a real time clock/calendar in it and a chip that reads temperatures from a thermocouple probe. I still have requests out for a few ambient air temperature sensors and a few other things that will be used in additional projects that will eventually connect to/from the roaster computer.

The surprising part is that the clock chip is more or less around the size I expected (about guy little/pinky finger nail sized) BUT that the temperature chip is significantly smaller than I expected. It’s REALLY small. It’s so small that you could literally put at LEAST 16 of them on top of a single computer laptop keyboard key.

I am still waiting for the “brain” starter kit to arrive. This is where things get funky. When I ordered it the availability date for it and the ethernet card were listed as June 28th with an estimated delivery date of June 30th. This is good because I’ve got some free time from then until the middle of July so that arrival date was going to be good to let me work on things some. Today, though, I get this email. It now says that the ship date is changed to July 30th. My online invoice still shows the ship date as June 28th. The microchipdirect.com website says the availability date is July 2nd. So I’m thinking my chances of seeing this anytime soon are completely random and probably not likely.

Ordered parts this weekend for roaster controller.

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I’ve ordered some parts from Maxim/Dallas as well as from Microchip this past weekend. The stuff from Maxim is supposed to be coming US Postal Service so I don’t really know when they will arrive. I forgot to add a temperature sensor (ambient) to the order though so I will need to come back to that later. I need to compare it with a similar chip offered by Microchip to see which one I want to use. I believe the chips by Microchip are actually smaller and more accurate but I will need to confirm later.

According to Microchip’s website / my invoice the IO board, graphics board and LCD touch screen, Prototype cards, and a 9V Power Supply will ship sometime in the next couple days. They are scheduled for arrival on the 17th. The Network Card and PIC32 Starter Kit is not due to be available for 2 weeks and is supposed to arrive on the 30th.

Building a roast controller system.

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As alluded to earlier in the blog I am intending on building a roaster controller system.  I’m probably a bit of an over-achiever in terms of my projects because every time I create something on the internet for one of my websites, as part of a building project in the yard, or whatever else I’m creating I always over-analyze it.  In my career one of the areas I’ve been responsible for was “Disaster Recovery” planning for computer systems.  In other words my job was to over-analyze all the things that could go wrong and figure out a plan to deal with them.  At the same time I also have to plan all the ways for it to go right and have a plan so anyone can do it even without strong computer skills.

Focusing on a roast controller as mentioned I’ve already purchased some testing equipment for measuring temperature using a K type thermocouple. I am now finalizing the equipment that I’m going to use to build this and test it.  I’ve focused on using the PIC32 microprocessor due to its abilities to work easily with Ethernet, LCDs, and having many input/output circuits.  In addition it seems to be a robust platform for RTOS systems allowing a lot to be going on all at the same time.

To ease development I am choosing to embrace the development tools provided by the manufacturer.  This of course adds to the startup cost of the system but allows me to “try new things” in the future too using the development platform.  Once I finalize the project I would then order the individual components and manufacture my own circuit boards.  To start off I expect to need the following.

The Starting Parts

  1. DM320003-2 – PIC32 USB Starter Kit II – $55.00

    • Main processor (MCU) test board.
    • Contains PIC32MX795F512L processor.
    • 80 MHz with 512K Flash, 128K RAM. (this is actually a lot for a simple coffee roaster but is necessary for drawing graphical LCD, developing complex roasting profiles, and loading Ethernet overhead.)
    • Allows USB, Ethernet, LCD, I2C and SPI communications. 
  2. DM320002 – PIC32 I/O Expansion Board – $72.00

    • Connector to access pins and interface auxiliary boards.
  3. AC164132 – Fast 100Mbps Ethernet PICtail Plus Daughter Board –$49.99

    • Physical wired ethernet board for interface to DM320002.
  4. AC164126 – Prototype PICtail Plus Daughter Board – $20.00
    • Prototype boards to solder additional parts and extensions such as temperature probe chips, time devices, relays, etc.
  5. AC164127-3 – Graphics PICtail Plus Daughter Board with 3.2 Display Kit – $154.99

    • SSD1926 Graphics chip (kind of like a video card)
    • 3.2 QVGA (240X320) TFT LCD with 18-bit parallel RGB interface
    • Touch Screen

The Later Parts

The above parts allow me to start testing User Interface functionality without worrying too much about the circuit boards except for the occasional prototype board communicating with a sensor or two.  I’m doing that to determine the final touch screen configuration and “what is possible” on the screen real estate to determine if I want to pursue additional sensors and features.  It will also allow me to begin testing response time of various sensors on the prototype boards.  Some parts I expect to need:

  1. MAX6676 Thermocouple Amplifier
  2. DS3232 Real Time Clock
  3. Lots of resistors
  4. Lots of capcitors
  5. Various Transistors
  6. Lots of diodes
  7. Photosensitive PCBs
  8. PCB etch Chemicals and developer
  9. SMD soldering and hot air rework station
  10. Infrared circuit board pre-heater station
  11. Small Drill Press w/ bits for drilling PCBs
  12. Oscilloscope for dimmer testing
  13. Several relays and/or some dimmer circuits that need to be designed still.
  14. Probably a video camera at some point to demonstrate progress/results.

Roast temperature probe sweet spot in Fresh Roast

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As I mentioned previously there appears to be a “donut” shaped sweet spot in the roast.  I had been testing my SR500 with a K type thermocouple in various spots.  Most of the time people run their roasters with the thermocouple shoved straight down the middle in a lot of the photos I’ve seen.  With the SR500 I’ve found this region to be very sparse with beans due to the high flow of air up the middle.

As shown in this diagram the center portion at the bottom shoots up the middle in the air column grabbing beans on the edges of the two green zones.  They are then tossed outward in the orange circular zone represented on top.  The beans that sit out on the purple areas on the bottom tend to burn due to low circulation.  Ultimately I would expect some sort of triangular slanted chute sealed to the edge would allow beans to be directed away from this burn zone and closer to an area where movement would be possible will help improve this.

I have not written much lately because I’m currently not at home using my roaster.  Prior to leaving I did some testing of the sweet spot ultimately getting pretty close to the middle of that sweet spot.  No matter which beans I roasted and the length the beans were being roasted I always noticed, while adjusting fan and temperature settings on the controls, that the beans always had first crack at the expected temperature +/- 1 degree Fahrenheit.    The same with second crack seemed to hold true as well.

Based on those readings and the reproducibility of that it is my opinion that the ideal thermocouple position in the SR500 and probably the SR300 is as I described earlier.  The height seems to be just below the surface of where 120 grams of beans fills the roasting chamber to for the tip.  This keeps it from the bottom where the heat is somewhat higher and allows it to be centered in contact with the main mass of beans once they expand slightly and begin to float more easily in the air column above his position.

Regarding the coffee’s I’ve roasted.  I previously mentioned some by name and certain characteristics of the roast as I was roasting them.  I had decided until I can track the actual temperatures and accurate times to share it was probably best not to continue posting the resulting curves as I roasted them.

Experimenting with a thermocouple.

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So now that I have a faster responding thermocouple I’m finding that the  sensor works better closer to the edges of the roaster.   When thinking of the bean mass on the SR300 and SR500 you probably need to consider the bean mass as if it is a donut at the bottom of the chamber.  You want to get the tip of the probe centered in the middle of the donut and not the middle of the chamber.

Most modifications people have shown put the probe drilled straight down the middle.  This has the advantage of clearing the “chaff grate” on the sides down a natural hole in the roaster.  The problem with this is that the very center is actually a sort of “fountain” of beans and hot air.   The probe has very little contact with any of the roasted beans and is mostly picking up the air put out by the roaster.

Many people who have sensored this middle area report temperatures in the 420 to 425 degree range.  At the very end all of the beans are very fluid and filling almost the entire chamber area moving freely.  Once this finally happens the temperature readings then reach the 440-450 range showing a typical second crack area that coincides with actual second crack occuring.  Often second crack ACTUALLY happens while the probe is showing 400 degrees when placed in the middle.  This is likely due to the bean mass thermic reaction being hotter than the air rushing up from below and only a few minutes later does the air column catch up.

I’m starting to get low on beans from the samplers  with only a pound or two left of all the varieties.  I’m feeling that the probe placement I used initially in the middle helped stall a few roasts due to inaccurate temperatures of the bean mass that I responded to.  I’m testing a roast where the probe was moved closer to the “donut” range to see what sort of tastes develop but this one is pretty close to a standard roast.

My feelings are there is a “donut” sweet spot.  In the diagram below there is a Orange region [1] that is the normal plume of bean being pulled from the middle area on the bottom and [2] tossed up on top to the left and right.  As you descend into that area you enter part of the sweet spot [Green].  In the far left and right corners [Purple] you have a “burn” zone due to very low circulation of the beans.  This is caused by the more central area of the donut [3] falling towards the middle and then being jetted to the top [1] repeating the cycle.  Only when the beans have sufficiently roasted does the bean mass begin to rise above the initial [Yellow] fill line.  As the mass makes it above the silver metalic band there is enough movement to cause beans to leave the “Burn Zone” and make it easily into the column.  This initial burn area is where the stray first cracks are likely to originate and the uneven roast occurs.

Freshroast "Sweet Spot" created in roasting chamber.

I would thus interpret the space where the D on the left donut and the t on the right donut would be the approximate ideal locations to sample bean mass temperatures due to the piling on of beans from the fountain [1] above it.

Freshroast SR500 apparent “safety” mechanism. Adding new thermocouple.

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Due to the microprocessor installed and the sensor mounted at the top of the roaster base where you install the roasting chamber.

NTC Thermistor mounting

It appears that when you turn the roaster on to High and lower the fan knob to the lowest setting the roaster will reach (unloaded) 430 degrees.  At that point the fan automatically revs up slightly (possibly due to the heater being off)  and the heat stops climbing at 433 degrees.  Occasionally it drops sooner but always between 430 and 433.  It then drops from 430ish degrees down to approximately 420 degrees and then resumes climbing again.  The heat appears to always stop at 420 and then goes back up.  The highest it stops dropping at is 422.

Temperatures were measured with a new K type thermocouple mounted approximately where the center of the bean mass would be.  I obtained this at OSH (Orchard Supply Hardware) since I needed some sort of multimeter for the moment.  They had one inexpensive “Craftsman” model with the ranges I need for measurements with the Digital Multimeter side with an included K type thermocouple mode.  I’m expecting the thermocouple to not last very long due to the temperature rating they put on it.  I will likely get one from eBay or something that is compatible with the K thermocouple sensors in the meter.  I’m guessing the protective covering they put on the tip end insulation area to keep the insulation from unraveling is not able to withstand the high temperature for very long but the insulation looks like it can take a lot more.   I’m going to probably get some high temperature silicone and put a little dab right at the end above the tip to hold the insulation better so it won’t fray.

Ultimately I’ll source out a thermocouple that can do more properly as I get further into this.   I’m going to switch to using the previous thermometer as a timer (was a secondary feature… you get one or the other on screen at any point in time) and the thermocouple as the new temperature sensor since it actually responds faster on temperature changes.