Tag Archives: electronics

Pretty on the outside and ugly on the inside prototype

By | | , , , , , , , , , , , , , ,
Leave a comment

So I’ve been busy doing a bunch of computer maintenance and looking into other things I’ve neglected while building the roaster so it’s been a bit slow.  I decided I wanted to start gluing corners together and drilling some holes to see how the case goes together so I can eventually get back to fixing the issues with the roast controller case.  Over the past several weeks I soldered together all of the boards, made wiring harnesses and figured out a bunch of “oops” moves I had made designing things when I got rushed for time.

Turns out I was not able to get stand offs locally in the sizes I had wanted so the heights are all screwed up where I placed holes on the outside surfaces.  I also forgot to specifically allocate power for the exhaust fan in the original design BUT I did have “Spare” pins allocated. The fan I ordered also was not the right size for the hole template I had used (Inside fan dimension vs outside screw / case dimension)… neither of them were actually labeled right the way every other fan I have is sized.

So with everything screwed or harnessed in place this is what I have for the Arduino…

The Arduino wired for Coffee Roaster control

It is a MEGA2560 mounted on a Crib for Arduino.  On top is an Ethernet Shield w/ microSD slot.  Then I used a variety of crimped headers to connect to some of the pins on the MEGA and on the ethernet shield.  I have twenty five lines in the bundle going to the Arduino.  I had some spare 10 strand cables from a project at Halloween and no 25 strand cables to use so I used one of those cable wraps to keep the all together after connecting DB25 to one end and header pins to the other.  Once the lid for the crib for Arduino is in place it then connects to the back of the enclosure.

Wiring Harness connecting to the back of the controller enclosure

As you may notice the sockets I was using for connecting the power out are the type that snap in.  The majority of these will not snap into most laser cut plastic sheets and instead are designed for aluminum cases.  The plug to the right on the other hand screws in.  These work great with a variety of thicker locations.  The fan was originally going to be on the inside with a wire cover on the outside but with the wrong size fan hole in use I had the wrong cover to fit the fans that I had that would fit the hole.

For the DB25 connectors it turned out good that I had decided to use a cut out pattern  that had the holes on the side for the anchoring hex nuts rather than just having them cut out so that I could mount them to the socket and anchor the connector.  Since the stand offs were too short they don’t allow me to anchor the PCBs to the bottom plate.  Instead I had to screw them to the back plate using normal screws and with the burnt circles on the laser cut work I had to use some washers too to keep it sturdy.  This is what the back plate looks like.

Rear Panel of controller

This panel includes – One non-filtered switched 15Amp Power Entry module, 2 snap in 15 amp convenience plugs, 1 5VDC fan, 2 DB-25.  The left one is the main guts for the LCD, TRIAC control, potentiometers, thermocouple, and a variety of other sensors.  The right includes all the non-essential stuff for backlighting all the buttons on the button pad and a few other things including spare wiring.  You cna see just a screw on the right since it was relatively intact and so it won’t block the DB25 plug being used.  The right DB25 has washers and screws in place.  These are primarily used to attached the PCB in place attached to the back side.

Next up is the inside view of the electronics area:

Rear View of the Back Panel

Rear view of the back panel.  I need to shrink up the crimp connectors around the wire  (they shrink like heat shrink tubing but is actually much firmer).  Also the connector on the right side (the switched power entry module) should have the screws more securely fastened with nuts and washers but this is mainly just a test to ensure it all fits together and then allow me to focus on some programming for a while to see if I can get more working and develop menus etc.  The clear acrylic bar is used to anchor the corners better.  I need to change the locations of the screws since I could not find screws the size I wanted without spending way too much for large quantities of them on the internet and having them shipped to me etc.  The thermocouple board on the right had the same issue with the stand offs so it is just floating loose in there right now.  I need to find somewhere to get the Omron thermocouple sockets where I dont need to order them by the 1000s since it looks like Ryan McLaughlin has stopped selling things on his site when they (used to) have problems getting the newer MAXIM thermocouple chip.  They’re all over the place now but he hasn’t restarted his store up so I don’t know the deal there.

Here is the view down into the enclosure from above:

Top view into enclosure

With the cover on:

Front panel installed on enclosure

Front panel running

Front Panel Running

When I send it back out again for a new case I hope to have a different board to install that will be switching the smaller breakout boards being designed onto the circuit board as well as add a power supply and possibly having an arduino board mated on top of the circuit board perhaps to bring more of the electronics inside.  I might want to try to get a Digilent board perhaps to try converting to it as a transition between Arduino and PIC32 before I completely switch to a dedicated PIC32.

I’ve also been looking at possibly creating a dedicated PC application to communicate with it directly via USB and over ethernet.  I am toying around with the “QT/QML” language but havent gotten too far with it.  I may just go back to Processing though.

RoastGeek Button Pad v 1.0

By | | , , , , ,
2 Comments

This weekend the final resistor I was waiting for arrived.  As a result I was able to solder the button pad board together and mount all the buttons.  I placed the board on my infrared preheater, applied some solder paste using the syringe dispenser on each of the pads, and then using a pair of Weitus tweezers started placing 0603 resistors from the piece cut from a reel.  I then turned the heater on and let it sit for a bit before turning it up a few more times until I got close to the temperatures I needed.

RoastGeek Button Pad v1.0 on Infrared Pre-Heater with SMD resistors placed.

Without a stencil it’s pretty hard not to goop too much solder paste onto the pads.  In most cases I had a suitable amount but a few it got a bit too much.  For most of the cases I had too much I removed some while it was still liquid-like from the preheater softening the paste.  I used the tweezers with a tiny bit of paper towel to wipe some away on the worst spots.  Solder paste is essentially  a mixture of a type of flux with a fine dust of the solder.  When the temperature gets high enough the flux material starts to liquify and the solder particles flow with the wet flux-like material towards the meeting point of the pads and the item being soldered.  As you apply a final amount of heat the solder particles melt and the flux-like material starts to evaporate/burn up.  To do this I used a hot air rework station to heat up the area near the resistors.  It has a pretty gentle flow that I can adjust with a knob so I didn’t have any issue of the resistors blowing away.  This tends to be a common problem using a hot air rework tool to solder SMD parts.  Once they were all in place I turned down and then a bit later fully off the heaters and allowed it too cool down.

0603 Surface Mount Resistor soldered to the board with an infrared preheater and a hot air rework tool.

Once the surface mount resistors were in place I tested each pad on each side of every resistor and confirmed that the correct resistance was measured.  This was to confirm that I didn’t have any “over gooping” resulting in the resistor being jumped by solder underneath of it.  Everything checked out ok so I continued on to mounting the buttons and header pin connections by hand with a standard iron.

RoastGeek Button Pad v1.0 with buttons, caps, and headers mounted

At this stage I tested the board with an Arduino sketch and was able to measure each button as expected.  This board has a much more accurate number compared to the last board.  Each button previously would measure a number that ranged 3-4 from the highest to lowest reading.  This one is dead on for almost every single button except for 2 of them that vary by 1.

I then mounted the board to the back side of the control panel.  I discovered that the standoffs I am using are about 1-1.5mm too tall so I will need to either grind them down or find a different set of stand offs.  I’m thinking of getting some Nylon or ABS ones that have a self-retaining clip for the circuit board side and a threaded end for accepting a screw from the front panel.  I also need to begin wiring up some wiring harnesses to go between the LEDs and potentiometer over to the new board.

I’ll add a picture of the mounted board  here once that takes place.

First order of circuit boards from OSHPark.com

By | | , , , ,
Leave a comment

If you were following comments in one of the previous blog posts I just received my first order of circuit boards from OSHPark.com. This order included version 1 of my button board and a preliminary interface board to connect a variety of sensors and some of my other boards to an Arduino Mega 2560.

I got to experience the “joy” of being one of the initial test subjects for the brand spanking new OSHPark.com site. It actually worked pretty well and was rather impressive in terms of the graphical response you got from it. It would evaluate the files you uploaded and convert them into a graphical rendering of the finished product. When I ran my boards through the system I did notice that the silkscreen appeared to be NOT the rear/bottom view as the site described but instead it was the “Superman X Ray Vision” view. If you’ve used Eagle and a few other competing PCB CAD programs this is what you normally see when working on your board. Your test will be “reversed” or “mirrored” and the holes will be in the positions they would be in from above. It is thus like you are looking through the layers from above. I mentioned this oddity in my comments on the job but don’t know if they’ve resolved it yet by changing the code or changing the description.

The timeline for my order is as follows:

  • May 21st – Placed Order (T=0)
  • May 25th – Tweet @laen replied by @OSHPark reported that the system is not sending notices yet. Indicates board have been reviewed and panelized. (T+4)
  • May 29th – Received official email that said boards on panel for May 31st.  Notice website reports May 30th as panel date. (T+8)
  • June 7th – Received notice saying boards sent to the fabricator. Probably just an update to the software of the site and the boards were sent prior to this point. (T+17)
  • June 8th – Received notice saying boards received from the fabricator awaiting de-panelization. (T+18)
  • June 15th – Boards apparently processed for postage based on postmark. (T+25)
  • June 18th – Received boards. (T+28)

As mentioned I expect most of the dates to be unreliable other than the fact that it took 28 days start to finish.  The site still has not changed from a status saying my boards are waiting to be de-panelized and nothing about being shipped.  Obviously it is a work in progress.

Here is the collection of boards received

First order from OSHPark.com. My Button Pad board and the preliminary interface board to connect a variety of sensors to the external Arduino mega.

The spacing seems to be exactly what the CAD said it would be and the holes drilled seem to be very accurate and centered like they should be including some of the very small vias.  I will need to crack off and dremel/sand off the rough spots from the edges where the boards were connected together.

More pics:

Interface board

Button Pad 1.0 with several buttons placed

Button Pad v1.0

Button Pad 1.0 Top

Button Pad 1.0 Rear

At this time I am waiting for 330 ohm 0603 resistors to arrive.  They were on back order and should arrive in a few more weeks.  Once they arrive I need to use my infrared preheater to heat up the boards and then do a quick solder on each of the resistors before connecting all the various through hole parts.  Once that happens I’ll update with a new photo showing the finished boards.

Ordered more stuff – headaches and new replacement stuff

By | | , , , , , ,
Leave a comment

I had a “Chromalyte” LCD screen that came from EIO.  I needed some sort of cable for another thing going on at home and EIO came up having it in some google search.  It was cheap and the price for a similar cable from darn near anywhere else on the planet was about 5 times higher plus obscene shipping on top of that for something that ultimately ends up in a padded envelope and has $2 of postage on it.  Anyway this LCD was supposed to do 20 characters by 4 lines.  Currently I’ve been using a 20 by 2 lines LCD by Newhaven.  The Newhaven works great.  The Chromalyte?  Not so much.

I googled Chromalyte looking for a data sheet and figuring there may be some info somewhere on the internet about it and maybe using it on an Arduino project or something like that.  I noticed I kept finding pages for EIO.  I looked the product over and kept trying to find some sort of marking on it.  I looked at the data sheet found on EIO and it was pretty basic.

It mentioned using some sort of software available for download from Chromalyte’s website to test it from your Windows PC.  I figured maybe I could try that and tried harder looking for some sort of Chromalyte website.  I threw Incorporated into the search and still kept coming up with EIO.  I really started to wonder at this point and went to Archive.org looking for historical websites that were named Chromalyte.  What I discovered?  EVEN YEARS AGO Chromalyte dot com pointed to EIO’s sales pages.  Today?  It’s current contents?  It’s a GoDaddy “is this your website” listing.  But with the history seeming to always be EIO they don’t even seem to be a real company and are instead just a propped up brand name for EIO.

What made me look into Chromalyte so much that I was having problems with?  Newhaven LCD I can serial.print and serial.write decimal or hex codes to it all day long…. move the cursor around on the screen, clear the screen, put text anywhere etc.  Chromalyte? I print serial to it and nothing happens.  I throw in slash n and r to see if that helps and it doesn’t.  I try sending hex codes for all sorts of thing and nothing.  If I serial.write a clear screen it wipes the screen.  If I serial write movement commands and turn on the cursor I can watch the cursor dance around all over the screen.  I print more serial to it and nothing happens.  I serial.println to it? I get a white box IN FRONT OF the text and the line that I want anywhere I tell it to move the cursor to.

Is there anything about this in the data sheet?  Nope.  Anyone used one on an Arduino?  Not that I can find…. Heck if it wasn’t for EIO listings all over the place I don’t think anything comes back about Chromalyte at all.  I’d have to format some search keywords to force it to drop out EIO responses just to see if I could find anything else because when I searched for that name every entry for pages and pages came back as EIO.

The codes it uses are really bizarre compared to most other LCD brands available.  I think I found someone’s code ONCE that actually used a similar command structure for clearing the screen and moving the cursor but all of the other codes were different.  I’m not a stranger to writing to serial driven LCD as well as using parallel, SPI, and I2C to write to text and graphic LCDs.  This thing is just plain weird.

Sure I could probably email EIO and bitch about it but if this thing is this weird it’s just not worth it to me.  It was cheap enough compared to the hundreds and hundreds of dollars I’ve spent on all the other hardware to build a coffee roaster that it’s but a blip.  I just don’t see myself buying another one, ever.

If anyone out there can send me an Arduino program that DOES indeed work on a Chromalyte labeled as a c420a that simply clears the screen, writes Line 1 to line 1, Line 2 to line 2 and so on I’ll be amazed.  If such a thing does occur I’ll permanently install the screen in a project I’ll be doing later to read a flow meter and open/close a water valve on my reverse osmosis water system so that I can punch up a 1/2/5 gallon fill without needing to watch it.  I’m hoping to have it monitor my total water into the system and the output into a bottle and then monitor TDS sensors to gauge water purity.  Then have it alert me to change the filters and keep track of water input purity throughout the year.

To my girlfriend:  Yes I am too lazy to set a timer to track how long I’ve been adding water to a water bottle.  Instead I will design a circuit, solder up a board, write software for a microcontroller, and then mount the thing in a case so that I don’t have to set a timer so I don’t overflow the water bottle.  I know my limitations.  Building a system to turn the water off by itself is FAR easier for me to do.

So anyway today arrived a Newhaven NHD-0420D3Z-NSW-BBW as well as a pair of PCB solderable DB25 connectors, a bag of 100 B3F-1000 type Omron buttons and a few Maxim MAX31855 thermocouple ADC chips.  I figure I’ll make a board up that does 4 inputs at some point so I got enough to do that plus a couple spares.  I still need the sockets though.  Nobody seems to sell those except for Ryan McLaughlin.  After the MAX31855 that he switched to from the MAX6675 became scarce he shut down his store.  Hopefully he will pop back up sometime soon since his boards were really well made and I think he’d be a great resource for DIY’ers building smoker controllers and coffee roasters and other such things.

Anyway this weekend I will be doing my taxes and then spending the rest of time soldering pins to the Newhaven display and connecting it to the roaster controller.  This past two weeks I converted the entire roaster program over to Arduino 1.0 and updated all of the Libraries that I was using to the latest versions.  I few I had to modify slightly due to them not being 1.0 updated but the majority of them were available on the internet updated already.

The conversion to 1.0 made me make a note of all of the libraries I had used and begin to create a list.  If you look at the menu bar you will see “Resources” up top.  This allows you to pick an Arduino link and then get links that go to sites to download the current libraries if you are looking to build your own project.  I’ll be adding a few more projects and libraries that seem useful to DIY Coffee Roasters (and controllers) over the coming weeks too.

Roast controller now at full power.

By | | , , , , , , , , , ,
1 Comment

So I’ve played around with the PID settings.  I haven’t officially sat down and tried to do a “real” tuning since the processing app I’m using right now lets you play with different numbers and feed it back to the Arduino to tweak it.  As a result I came up with a few numbers that flattened out a lot more than it did previously.

First roast with crudely adjusted PID

Next I will need to take it more seriously I wipe out the configurations, dump some junk beans in, and fire up the roaster and calibrate until I can’t stand it anymore and then roast some coffee again.

In regards to the button controller I have figured out a layout that I will likely use but I’m trying to keep this accurate on the schematic system I’m working with to build a real PCB later.  For whatever reason the part in the system appears to not match every other part I’ve seen out there and what I’m currently working with.  I also need to go back to radioshack and buy a resistor I’m going to need because the big multi-pack I have doesn’t include that one resistor that I need to make the math work.

The last couple roasts with this new controller turned out decent enough.  After 3-4 days rest they had extremely good smells (but tasted only “pretty good”.)  Today’s two tests are MUCH closer to ideal roasting the way they worked out and the smells (and the smoke detector) agreed at the right times.  I’ve got two batches waiting that will get consumed over the next several days and we’ll see how it’s going as they rest.  I’ve got a single serve coffee brewer that’s working out better than some of the other ones so it will take me some time to work through all of the beans.

First test run of the Arduino FreshRoast SR500 Controller

By | | , , , , ,
Leave a comment

This afternoon when I was home for lunch I ran the Arduino control touching a light bulb plugged into the heater output.  It tracked the heat pretty closely until it got up around 300 degrees.  It overshot by about 10-20 degrees initially and then once it caught up it was pretty close the rest of the way pulsing the power as necessary.  After it neared 300 degrees it couldn’t keep up and started lagging.  At that point I left the fan running at full speed for the duration of a normal roast.

This evening I went out and plugged in the heater.  The heater is a totally different monster!  It tracks but it OBVIOUSLY needs the PID calibrated until it works better.  At low fan when the heater dies down it has a massive swing in temperature going under and then back over again.  It appears to only do ok at the lower temperatures and then is all over the place at the higher temperatures.  What is noteworthy is that it DOES track the same “slop” drift around the target temperature all the way up.  The drop/gain on the % power is simply too drastic and needs to be adjusted to flatten out more.

For giggles I’m throwing out for view a test graph as it ran (no beans) for a few minutes once with low fan and another with higher fan.  I have the heat maxed at 80% power in the program so that I don’t burn anything up accidentally until I’m sure it can run like it should.

First Arduino Roast Controller test with heater connected

In the lower graph it shows a low fan vs a higher fan setting.  The middle one is a heat amount that actually gets reduced to 80% in the code during testing.  The green in the top graph is the target while the red is the actual temperature reading. Both tests were run with the roasting chamber left empty.  I’ll try adjusting the PID settings a little bit to smooth it out to have smaller sweeps and then start loading some old green coffee in to test it with a “load” and see  how much that stops the swing.

Now that the heat is able to be completely shut off this helps the temperature drop a lot faster.  It’s my guess this would be better for the roaster overall to completely drop the temperature of the coils before turning it off while it cools the beans.  I’ve set the system so that the cooling requires the probe to reach a low temperature before turning off so the coffee beans should be quite cooled before it shuts down by itself.

Nearing a rough prototype roast controller setup

By | | , , , ,
Leave a comment

I haven’t had a lot of time to work on this project lately.  A few weeks ago I had ordered a variety of jumper/header crimp pins, housings, and tools to crimp with.  With those ends I’ve pieced together “arduino compatible” wiring harnesses to go between break out boards, arduino and to the perfboard and other pieces I’ve thrown together.  As a result I feel I am now approaching a rough prototype roast controller.

One of my other purchases was a “Crib for Arduino” to mount some of the pieces inside a box that were not already part of the RadioShack case pictured in my last blog entry.  Most of the crazy wiring on the Arduino photo has been woven together into separate bundles and connected directly to the DB25 connector cable which I’ve also been slowly crimping together.

I would have been testing the fan and heat controls last weekend (and when I had time this week) except that when I finally got it hooked up the fan and heat were no longer “smooth” but instead stuttered all over the place.  It had been quite a while since I had the Arduino side of it hooked up to the mains power so I had to go through and double check all the wiring in the harnesses and DB25 hookups.  Eventually I figured I’m either overloading it with the service schedule on reading sensors and writing to SD, updating the screen and not having time to trigger the mains voltage properly or else the timer wasn’t triggering properly.

Once I had confirmed all the wires were right I looked up the interrupt lines and timer lines in the Arduino website and realized the code probably had the wrong interrupt in there.  Several months ago while trying to clean up some of the code I remember having accidentally typed over the interrupt number in the attachinterrupt line and saved it without realizing it had been modified while updating other code.  Once I returned it back to the proper interrupt for the pin I was using everything worked again.

Tonight I tried running a load of beans through the roaster on fan only.  I believe my adjustments for the fan power are slightly off because the beans begin moving a tiny bit too far into the % potentiometer.  I’ll need to try running beans in an unmodified roaster and pay attention to the level of movement in both roasters based on the position of the knob.  If I had some sort of manometer it would probably help more but I don’t have one.  There are several DIY projects that appear to have built one that I’ve seen months ago that I might end up trying to look up again but I’ll have to see how well it goes without it.

This weekend I’ve got other things going on so it will probably be over the next week and following weekend that I try to calibrate the fan and then the heater.  Once I’ve accomplished both things I’ll begin testing the PID settings to see how well I can control everything to automate the roast

Once the automation appears to be working I do want to add a few additional sensors still.  I then will start working on an Arduino to PIC32 conversion of the controls adding the touch screen and using it to send instructions to the Arduino.  Then slowly migrating more and more sensors and devices back over to PIC32 until eventually I’ve eliminated the Arduino unless it proves helpful to have separate microcontrollers for specific functions.  There will probably be a basic Arduino compatible roast controller in between that will be built onto a PCB that will be professionally produced using one of the quick PCB prototype companies.

 

Arduino roaster controller with zero crossing dimmer

By | | , , , , , , ,
Leave a comment

With all the time I’ve put into the Pic32 roaster I’ve always had this nagging worry that any of my sensors may have had damage during testing. When you try to get something working and keep getting gibberish you need to find a way to rule that out. As a result I decided to purchase an Arduino a few months back to confirm everything works. Turns out (so far) that everything IS actually working and I didn’t damage any sensors.  In the months I’ve been working with the Arduino I’ve actually learned a few reasons why some of the sensors didnt work on the PIC32 the way I had programmed them because learning to program an Arduino is sooooooooooooooooo much easier and better documented for “average people” to figure out compared to reading the hundreds of pages of technical manual for the PIC32 that isn’t ACTUALLY even finished being written yet.  There is a ton of code out there to test every single sensor I’ve purchased so far on Arduino. In addition I decided it would be a great way to start the dimmer using zero crossing detection in a system that runs outside the PIC32 before I convert it.

My intention is to get basic functions working on Arduino, then get the PIC to talk to the Arduino to send it commands to switch power by itself while the PIC reads all the sensors and logs data and then decides what to do as it comes from the Arduino.  Finally it will eventually be migrated entirely to PIC32 when I learn more about the interrupts on PIC32. At the moment I’ve put together a board that takes in 120VAC and uses Q4015L5 Triacs and MOC3052 drivers to control power to two receptacles. It reads the zero cross on my power using a H11AA1 and gets an interrupt used to trigger power switching. During my initial testing I confirmed the zero cross detection circuit worked and switching the triacs manually on or off worked without  regard to the zero cross state. It unfortunately didn’t seem to actually switch automatically for some reason when I wanted it to dim.  After a few days of testing I realized the Arduino Mega and the Uno had the interrupt timer pins in different places.

Since this is the first mains power circuit I’ve worked on I started running it with a variac out in the garage (and then fed that out into the driveway at the end of an extension cord…) and gradually turned the power up from 0 to 120VAC testing each section as I built it to ensure nothing arced or got hot or burnt up.  During late November I hooked it to the Arduino and got it to begin adjusting fan and heater under PC control as well as using two separate knobs.  Later in December and January I got it to begin logging to SD memory and following a programmed profile.  After that I added a bunch of additional environmental sensors and mounted it in a RadioShack project case.

 

First working prototype in Radioshack Project Case

I’m now at a stage where I’m looking to consolidate the various sensor cards either down onto a circuit board or attached to a set of pins directly.  I’ve grown tired of accidentally unplugging random wires carrying it back and forth from the garage to my office area and out to the kitchen stove / vent at various stages.  My hope is to shrink it down to a much less complicated arrangement being mostly on a single circuit board and interfaced by a few short cables to the Arduino.  It’s a bit complicated currently and getting worse.

Jumble of Arduino stuff

For the Arduino I’m using the MEGA 2560.  It is attached to the power control box pictured above via the DB25 cable.  At this time the box only controls power but I’ve mapped out pins on the DB25 to use for future boards to allow sensor breakout boards from a variety of DIY electronics companies to plug into them.   I’ll break this out to various header pins that match various breakout boards so they can be directly attached.  I’ll probably also design positions for eventually soldering chips directly to a board later once I order them when I’m further along and jumper the headers into those sections.  This will let me test a circuit on the board while still ensuring it actually works with the breakout board first.  The board will be designed to replace the items in the RadioShack box using SMD parts in some cases where cheaper and more convenient to shrink the board down smaller.  I hope to have it all shrunk down and consolidated to a single board with a DB25 connector to get to an Arduino I’ll be mounting inside an Arduino Crib case.

FreshRoast SR500 Teardown – Part 3

By | | , , ,
5 Comments

Continuing the series of taking a Fresh Roast SR500 apart leads us to the internal heat / air mechanisms.  At this stage you have reached the components critical to any modifications of your roaster.  I’m updating this post in December with photos taken back in October when I stripped the roaster down the rest of the way and began building my modifications.

Part 1 we started with the external screws to gain access to the internals.  In Part 2 we separated the electronics between the high and low voltage and then lifted the high voltage board out with the heater/fan.  This left us here:

Heater / Fan and Power board assembly

We have now reached the point where we unplug the old roaster boards and start looking at attaching alternate controls.  At this point you are going to separate the metal connectors from the board (assuming you are replacing any of these parts or modifying it in some way)  You will have a black plastic cover from the top, a metal cone underneath that funnels the hot air towards the vented top, and a black plastic pan with a fan sticking to the bottom.  The pan will have three screws.  You see one of the locations to the left side and another to the right.  The third one is not visible in this photo due to it being on the back side of everything you see.  If you remove the phillips screws from these locations it will allow the top plastic piece to be separated.  The top metal piece is sandwiches between these plastic pieces and held in place with the screws mentioned above.  The metal piece is sealed to the heater mechanisms inside the bottom black plastic pan using silicone sealant.

Once you lift the top covers off and break the silicone seal you see this:

and this:

The fan is firmly connected to the bottom and up into the blades.  The fan is a straight sheet of metal leading from the middle out to the edges with a flat disc on top.  It is not apparently simple to separate and seems quite “stuck” in place.  The middle “axle”/hub of the fan does not appear to have an obvious way to disconnect it though I’m sure there is a way to do so.

Looking back at the heating area you will see the bimetallic switch and a temperature sensitive fuse.

In the center there are two bolts/nuts .  These anchor the top part of the funnel to the heater coil.  You will notice 4 spots that look like staples above.  These are how several supports made of the same material that the fuse and switch are riveted to.  There is a metal ring holding this all in place with a “washer” made out of the same material again.  This material is a high temperature material often used in heat guns, hair dryers, and popcorn poppers.  It is designed not to burn and to cool off quickly.  There is no point in disconnecting the nuts  you see and you are likely to damage something in the process when you try.  Immediately under the center part is a small heater coil that connects to the fan.  This coil always generates heat whether the system is on or in “cool”.  It is used to lower the voltage from 120 volts to somewhere close to around 20 volts DC using resistance and the resulting energy given off by the coil.  The remaining electricity leads out from the system to the “black box” rectifier on the bottom of the fan motor.  The outer coil is on the opposite side of the slit and continues all the way around providing the majority of the heat.  You can see the outer cool quite clearly in the photo below.

In the photo above and below you clearly see the temperature fuse.  This device is called a ThermoDisc Microtemp thermal cutoff.  There is a PDF that discusses the features of this particular device http://www.thermodisc.com/uploads/PDF-ecombro.pdf.  It also has a diagram of the inner mechanisms that make this work.

It is a Thermodisc G4A01216C 216*C Cutoff.  Once the red stuff melts (at 216 degrees Celcius) there is a spring inside that is released and it mashes the wire outside of the housing and no longer makes contact to allow the electric to flow.  Once it fails the only way to repair it is to bypass it or to put a new one in.  Since the mechanisms are anchored with a rivet they are not the easiest to source and replace but it is possible to do.

The last mechanism is a Klixon YS10 46b-s x9ab.  This is a Klixon YS10 Series 150*C Beryllium Copper Arm, Standard Length Terminal (31.5).  Normally once it triggers at 150 Celcius it then has to cool before it works again.  The reset is set to 90 degrees normally and some models has a different offset.  YS10 specifies the type, 46 is the temperature (150 degrees) b specifies Beryllium Copper (the bimetalic switch material) -s for standard.  In the X9ab position this would possibly be where a different temperature reset amount would be specified.  It does not clarify the numbers used there.  It appeared in the PDF linked above as (XX) in the part number.  This MIGHT be that it needs a 9 degree temperature drop on the switch before it engages again assuming it uses an X as a place holder rather than using a 0.  Since it is not in parentheses this might simply be some sort of a plant number or production date rather than a temperature offset.

 

Modification:

Many modifiers like to disconnect both the fuse and the bi-metallic switch.  I do not advise this unless you are absolutely sure what you are doing.  If you wish to use the center heat coil separately or with the main coil together this is up to you.  You will need to disconnect the white wire that leads to the fan by prying open the brass clip (under the heat shrink) and supplying your own transformer to around 20 volts AC to independently control the fan.

At the moment I’ve been using an Arduino to control a Q4015L5 triac with a MOC3052 and a H11AA1 as a zero crossing detector. There are two triacs each used to separately power the fan and the heat circuits. Each side’s gate is triggered with a MOC3052 opto-isolator by a single pin on the Arduino to a resistor through the moc’s infrared led and on to the ground pin. The H11AA1 works the opposite way triggering a led on the high voltage side and it measures the fall of the 60hz sine wave of US electric.  Each fall signals the Arduino on another pin that is connected to a hardware interrupt on the processor. The interrupt sequence compares the fan and heat potentiometers to a map and then uses the lookup value to set the length of a processor timer. The timer then comes back and fires the fan or heat pin that fires the MOC3052 linking the triac and connecting power from the input side.

I disconnected the white wire from the fan and routed it with the primary heater coil so that they both run at the same time. On the fan side I connected it to a transformer from Radioshack that outputs 25VAC. This appears to adequately run the fan and delivers more air flow than normal due to the fan being “overdriven” from it’s normal voltages. While this is not good for long term use this could be useful if properly triggered in the programming for cooling and drying or initial heat up. In other words turn heat on at 70%. Start fan at 120% Gradually drop fan to 100%. Increase heat to 100% while dropping fan to 60%. Etc…

While running the system from a variac and through a watt/amp monitor I found the fan consuming approximately 50 watts at the original 100% air flow on through the new maximum around 70 watts for a 125 to 130% flow rate. Once I turned on the heater I found the original wattage level use set at 80 to 85% heat and what seemed like a normal heat output felt by hand in front of the output. Lately I had been getting around 1520 watts with momentary flutters up to 1580 at high and full fan before bypassing the controls. Now at 100% it was showing upper 1600 to 1750 watts for the brief few seconds before I turned it down.

I’m pretty certain this is not designed to run like this and would likely melt something if left to run this way on it’s own without some sort of “safety” override in the programming. What I would expect to be necessary is to mandate original 100% air flow before the heat can be turned past the usual level and the fan cannot be lowered until a specific number of seconds after the heat is dropped to a normal number. Additionally there should be a limit on the duration of this heat overdrive. This would be used to help drive the roast in a way many home roasters like to use to try reserving some heat until towards the end to drive it to second crack or some other nuance.

This should be thought of as some sort of reserved “afterburners” to a skilled pilot used only when necessary or someone pushing a nitrous injection button on a race car or turning on some super charger.

Once heat has been disabled it clearly cools off much faster than before. As of 10/10/11 I’m waiting to more firmly mount all the controls and switch to the new potentiometers before testing a roast. I also have a few buttons for start/stop and a microSD logger to setup first before I start this because I want to track thermocouple readings vs each of the percent settings etc so I can review it later after my first test. If anyone has a way I can sense the wattage use and feed it to the Arduino too please let me know. I’ve seen a few very LARGE devices intended for whole house sensing but I’m looking for something small….

FreshRoast SR500 Teardown – Part 2

By | | ,
2 Comments

Welcome to Part 2 of the FreshRoast SR500 Teardown. In Part 1 you saw the basic steps to open the SR500 properly. This article will explain how to continue a teardown a FreshRoast SR500 roaster into the various components and probably give insight to similar pieces in a SR300 as well. If you are looking to modify an SR500 the following content will be the best starting point for understanding what makes your roaster work as it sits. It will include technical information about the components that make the SR500 work. Part three will begin to make suggestions of where modifications will need to take place if you wish to split fan and heater control to external dimmers, VARIAC devices, or otherwise control your SR500 with a Microchip PIC, Arduino, or other microcontroller or PID controller device.

This article was made possible by having purchased a spare SR500 base that can be completely broken down and tested upon. I will be using this base to interface to my roasting computer.

You should refer to Part 1 if you need assistance opening the roaster. Most people should be able to open the roaster without the first guide but it is a good idea to review it briefly to become familiar with what you are getting yourself into and deciding if you are up to it getting inside. Most of the connections are very “coarse” and use through hole parts.

For my project I am going to be using surface mount parts which requires a bit more skill. There are many options out there so if you are looking to simply use something like a 20×4 character LCD you can probably find a way to do this without the surface mount parts. If you want to continue with a graphical LCD like I am you will likely need to learn about more advanced methods of soldering.

If you are unsure you should research and contact a “Maker” or “HackerSpace” club in your area. Examples of such include NoiseBridge in San Francisco. There are plenty of other groups throughout the USA as well as in many European countries. The closest one for me is about 3 hours away unfortunately so I’ve had to resort to figuring most of these things out on my own. Coffee roaster computers are a pretty popular thing out there so you can probably find other reference material out there.

Most of these groups offer classes in soldering as well as often having capabilities to help design/build enclosures, mill parts, create circuit boards, and have shared equipment for laser cutting, CNC milling, 3D printing and many other systems. Not all groups have these amenities and many require you to demonstrate a level of mastery, take classes, or otherwise “wait for time slots” on the items of interest. Hackspaces normally charge a monthly membership to participate and use the facilities but usually have forums, IRC channels, and other such things where you can find out more information before you commit to driving for a visit.

Removing the inner parts of a FreshRoast SR500 Coffee Roaster

You will need:

  • A small phillips screwdriver.
  • A SR500 Base with the bottom removed (SR300 may be similar except for changes to the microcontroller board)
  • A baggie or small tray to hold screws
  • A clean area to work
  • Optional: Items to label the wires removed. This should be done as you unplug each wire so there is no confusion.
  • Recommended: Needle-nose pliers to grasp some of the flat connectors and pulling them from the circuit board.

Step 1: Unplug your SR500 from the wall and remove bottom as described in Part 1.

FreshRoast SR500 Interior

Step 2: Identify the high voltage power wires inside the case leading from the main black wall power cable and detach them (N and L1)

It is absolutely critical that you have unplugged the power before performing this step or you will be electrocuted.

The wires you need to remove are labeled N in the middle of the board and L1 on the JP2 side lower down on the board. Normally this would be Neutral (N) and Load (L1). Normally in most North American electrical devices you would not label things L1 and L2 unless you intended to have an L3 for three phase electric or were enumerating your loads. Since the wall plugs into one of the L’s and the other goes to the actual load this seems a little odd but I can follow the reason. Regardless, both will need to be removed to lift the circuit board and heater system up out of the enclosure. You should use the needle nose pliers to grasp the connector and pull it up. Grasp it by the metal and not the wire. Pulling by the wire will rip it out of the connector requiring it to be replaced with crimpers and appropriate ends. You should try to support the board so that pulling the ends do not put additional stress than is necessary.

It is ok to slide the circuit board up some as shown in the L1 photo. It will be difficult to lift the board up very far prior to removal of the N and L1 wires. Again, support the board as you use the needle-nose to pull the wires off.

N on right between 100W and JP1

N on left between 100W and JP1

L1 on Left below JP2 and MOC

L1 Removed below JP1 and MOC3043 chip

N removed

Step 2a: If desired during step 2 above or 3 below you may wish to remove the power circuit board from the PCB guides in the enclosure.

Gently slide the power board upward on both sides trying to clear the top edges. This may be difficult to do and is generally not necessary until you wish to remove L2, 100W and 1000W.

Power Board being lifted out of guides

Step 3: Remove JP1 and JP2 low voltage cables.

Both of these cables are low voltage and will come off easily when pulled. JP1 connects to the main logic board with the Atmel CPU and front control panel. JP2 connects to the Fan Speed Control potentiometer.

JP1 Removed

JP2 Removed

Step 4: Slide heater/fan assembly out while looking for the NTC sensor cable.

Do so slowly because the NTC sensor is still attached to the main logic board. Once the heater top layer begins to slide out of the enclosure you should try to find the wiring coming from the side of the heater. If you removed the circuit board from the guides pay attention to it as well so that it does not catch on anything.

NTC Sensor on Heater Enclosure

Identify the connection on the main logic board and unplug.

NTC Sensor connector

NTC Sensor unplugged

Step 5: Inspect the removed heater and power control board.

Heater / Fan and Power board assembly

You should be left with a loose middle portion of the enclosure with the main logic board still attached.

Middle Enclosure with Main Logic Board

Put it to the side and continue with the power board removal.

Step 6: Remove the 1000W, 100W and L1 cables to separate the Power Control Board.

Using the needle-nose pliers pull off the 1000W, 100W and L1 cables from the Power Control Board. This will allow replacement, modification, or other inspection to occur more easily.

As mentioned above L1 and L2 are a little odd in North American wiring but regardless the white wire is the Neutral and Black is the Load typically. Since we have 1000W and 100W and one has black and one has a white wire this continues in not complying with North American wiring standards and there are other reasons this roaster is abnormal with wiring so we will disregard this in thinking about the roaster. The 1000W connection white wire comes from a large outside heater coil and gets fed power from the L2 connection. The 100W side requires voltage to be applied to L2 and will operate both the fan and the small center heating element.

The 100W side heater to fan wire connects to the bridge rectifier on the base of the fan motor and is wired this way to use the heater coil in the middle to provide resistance to drop the voltage to a level acceptable to run the fan. The black wire side of the bridge rectifier is connected to the 100W connection on the power board creating a second complete circuit. The fan itself (after the rectifier) picks up its power on the other 2 wires once the internal mechanisms “do their thing” in that bridge rectifier. There is a capacitor jumped across the rectifier and I’m not very familiar with rectifiers and using a capacitor but I would guess this has something to do with the zero crossing and trying not to “sputter” when the power cuts out momentarily since this is DC for the motor and AC for the power source.

Alternate angle of power control board.

JP1 is labeled with J1 through J5 positions. J4 and J5 go to pins 4 and 5 on the MOC3043 chip. This is for microprocessor control of the attached devices. The board appears to have spots of solder placed on each of these that look like a “via” that someone tried to solder over but there does no appear to be a real via on this board since it appears to be a single layer board when viewed in front of a bright light. I’m not really sure why those spots are there. If someone has any ideas please pass them on and I’ll add them here.

J3 connects to the Neutral connection. J1 appears to go around the edge of the board linking to the fan potentiometer circuit and the BTA08 (Q6) trigger. J2 leads directly to the BTA16 (Q5) trigger.

Electronics and Connections Analysis

Normally in home electrical work you are required to switch the load side on or off prior to whatever object gets the power. For example you have power going to a light switch. The wire that comes out of the switch then leads to the light and then the light connects to neutral. When you flip the switch you supply load power to the switch, the light then illuminates, and then it passes the electric to neutral completing the circuit. This is typically a safety measure so that you can change light bulbs and particularly remove broken ones with the power off and not get electrocuted as well as generally being good practice in case of almost any other malfunction. This is not how the roaster is wired. If you had the ability to touch either the fan or the heater coil while it was plugged in but not running you would get electrocuted because they appear to be always live. Since they are physically enclosed it is not as important but will affect how you control the roaster.

The slide switch on the front and the cool/up/down adjustments only control the (right) gate sides of the two triacs. This gate is like a light switch. Normally this is a high voltage that is triggered by an opto-isolator chip. The MOC3043 inboard does this for one of the sides while other circuits trigger the other side. The other pins of the triac are the high voltage switched side connections. Both the 100W and 1000W neutral wire connections lead to the middle triac pins of their respective sides and are then gate switched to the wall Neutral pin in the middle of the board on the left side of the triac.

The 100W side’s use of the heater coils is used to drop the voltage by resistance to the fans rather than using transformers or other devices to provide lower voltage to the fan. It is more important as a voltage control than it is as a heater. The fan being connected this way results in some heat being generated whether you are in the cool cycle or not and would vary with the fan speed. Obviously changes in heat are slightly mitigated by the air flow. To fully control the fan separately from all parts of the heater you would need to separate the white wire side and route it to neutral while supplying power separately to the fan by a transformer to control the voltage or else completely remove the bridge rectifier and control it by DC power directly. 100W of heat is not very much and is likely not much of a concern and certainly not really useful either as a reserved heat source. Watching a wattage / amp meter in real time when the fan (with small coil) is running shows about 125-150 watts of power use at full fan. The 1000W side full heater bumps wattage into the 1450 to 1520+ range when supplied a full 120VAC.

The 1000W connection white wire comes from a large outside heater coil and gets fed power from the L2 connection. If you were to separate both of these wires and plug them into wall power you would get A LOT of heat being generated. The 100W side requires voltage to be applied to L2 and will operate both the fan and the small center heating element. Both of these when plugged in separately operate normally. Together I had some issues keeping the fan running once the fan side circuit is set to full power and the heater exceeds half power but this may be due to a faulty potentiometer I was dealing with. Ultimately I wanted heat totally separate from fan so I bypassed this with a transformer entirely and have a different set of potentiometers to install soon. I also switched from neutral gate switching to load side switching.

The fan does not appear labeled with any part numbers or any indication of voltage requirements. Based upon the common construction of many other air roasters and specifically a DIY favorite, the Poppery, being almost all similar it is likely to be a 20 volt fan and runs higher than 1.5 amps at the top.

As shown in Jim West’s blog entry about modifying a poppery http://popperyii.blogspot.com/2011/01/completing-hiros-journey-poppery-ii-mod.html (not affiliated with this site nor endorsing my modifications) the use of a transformer is probably required on the fan if we separate things fully and wish to control fan alone without a lot of complicated electronics. Use of a transformer is more expensive than some of these other options but it is quick and easy. Jim’s diagram of the heat system with the labels for each connection point is identical to the FreshRoast including the safety mechanisms. Those mechanisms on the FreshRoast, however, are calibrated to higher temperatures than what is allowed on a Poppery so the FreshRoast is much like a coffee calibrated poppery.

As a result I would hesitate to agree with anyone removing any of these devices like happens with a Poppery without being absolutely certain of their choice and without building in a lot of additional mechanisms. Pay attention to the old and new schematic areas for my point about the way this is wired. Running the fan alone on a variac at lower voltages works fine. As it exceeds the 20 volts area it begins to show the constant glow of an arc spark in the motor and may arc outside (dangerously) at higher voltages. A transformer is likely to be the easiest and safest solution.

Possible SR300 Fan Speed Modification

On the rear of the “power control board” above it has a silk screen label P/N:306171. I believe this is probably going to be the same board found in the SR300. On the SR500 the socket labeled JP2 leads to wiring on the rear marked R29, R30, and D5 on the “left” side. The position for R29 has no resistor installed on a SR500 but it appears to still have jagged solder and scrape marks on mine.

I believe this is a pre-assembled board made for the SR300 that is tested this way and then forwarded to the roaster manufacturer. My guess then is it is allocated to a SR500 where the manufacturer manually removes R29 and installs it in the SR500 case connecting a potentiometer that is installed on a SR500 panel assembly.

If JP2 exists and is unused on an SR300 the R29 might be able to be removed and replaced with a potentiometer using the JP2 (or holes for it). The front panel might then be drilled and the potentiometer then gets “creatively” installed. I’m going to guess that the plastic is probably already shaped for it and possibly drilled too because it’s probably easier to just put a different gray “sticker” on top depending on the roaster being made.

No impression yet on the “brain” bits of the roaster low voltage board and if the heat switch can be adapted. I would expect this part to be unique for each roaster model unless the installed switch only gets wired to the “High” and off positions of the board and excludes the middle and low position being connected to anything.