Thank you John. I am really only a hobbyist

As for the darker roasts issue. I seem to belong to a totally different doctrine of thought, but still, my whole family and culture are definitely on your side .

To me, that's one of the fun parts of home roasting, you can take a bean, and roast it to different levels, and see what you like. Lately, I have been roasting to the start of 2nd crack, but I think I am going to stop sooner next time, and check the results.

When I was first learning (a week ago ), I unintentionally stopped the roasts too soon, and I did not really like the results, too bright for me. I like the chocolatety taste you get with a darker roast, as long as you stop before the burnt taste kicks in

randy

Orwa,

Thank you - seriously it's nice to see the creative hobbyist at work and the trials, struggles and ultimate combined results. The circuit is super.

As for doctrine, culture and style of roast - I absolutely agree. Each person has their own view and that is what makes it so special...I found that once, that Popper actually when I was not watching it burned a set of beans, they turned almost to dust when ground...the flavor was very strong but not bitter.

What I am seeing is that with that popper one need the controls and mechanisms you installed and built up to v. the stock Popper. The stock Popper with a tilt and a stirring can do well, but one needs to really watch it.

I made some of my first SO (single origin) and was not so sure I liked it - a bit light. I've tried the hard bean and it was ok. I prefer a combination of Brazil Santos, Uganda, Yehem (mocha) or Zimbabwee Fancy and a 1/3 decaf Guatemalan. I like the chocolate flavors v. the lemon and brightness....I really don't drink much coffee just a shot or 15ml of it occasionally with milk steamed...

Thank you again for your comments and guidance in this control circuit...very refined.

You are totally welcome

As to the improvements/refinements that can be made to this modification, I may suggest the following:

1) As for the DC power supply, I said I used an original TOSHIBA laptop charger, which happens to be the one I once dumped. Nowadays, many laptop chargers are smaller in size than the one I used, and can be easily fitted within the roaster. This cancels the need for the extension I added and has a number of advantages. One of these advantages is that it could fit tightly within the case of the roaster with no need for any untidy fastening of the charger (in my case it could easily slide out if pulled with force). Moreover, the charger I used can provide 5 whole amps of current of which I am only using 1.65 amps for the DC motor. The smaller-sized chargers will usually provide 3 amps of current which is still more than enough for the fan motor. Still, there is the possibility that these smaller chargers will not provide 15 volts, but rather will provide something like 19.5 volts, which is still great given that the linear circuit shown above can handle up to 32 volts for the "voltage in" terminal (i.e. you could easily design the circuit so that the output will not go beyond a certain voltage below the supply, such as 12VDC for example). Note that it's possible that the DC motor that exists in these poppers could run on any voltage between 3-24 volts DC (which is the case for many DC motors), in which case someone will have the additional BIG advantage of a much greater maximum airflow (which the decisive factor in my opinion in allowing you to roast bigger batches).

Note: In my place, original laptop chargers of both sizes are sold for around 160 S.R. ($42), whereas the commercial (non-original) ones are sold for around 80 S.R. ($21). This makes this part of the modification the most expensive unless someone manages to have a less expensive DC switching power supply that provides the required voltage/current (there are many, many options around us that could be much cheaper than a laptop charger). The current required for the DC motor in my case was 1.65 amps when provided with 15 volts.

2) As for the panel current meter I used, which is an industrial one, I think it's very big and annoying. It's annoying because: (a) it's scaled up to 20 amps rather than only 5 (b) it's very big compared to its relatively-basic functionality and (c) it's not directed upward and hence I always have to lower my head to observe it. Moreover, I bought this meter for 50 S.R. ($13), which is actually expensive given the fact that the price of a hand-held analogue multimeter in my place could be as low as 10 S.R. ($2.6, made in China). Again, it's not about the money but rather about the fact that an embedded multi-meter could have been actually neater and easier to deal with (with its smaller size and with the five amps occupying the whole range). In my case, this was the most expensive component of the modification since I already had the DC power supply in hand.

3) In the case of using spacers and increasing the height of the machine like I did, the chaff will inevitably get into the inside of the machine (due to the gap between the lid and case of the roaster). This can be fixed using a strip of a metal screen that fills the gap, which can be fastened to the lid using the same screws that I currently use for hanging the springs.

4) For sensing the temperature. The approach I suggest is to embed a thermocouple probe in the machine (which is sold separately), and to plug this thermocouple into the multimeter at the time of roasting. My suggested sensing point is the middle of the roasting chamber (the perforated metal cup within which you roast the coffee), and to pass the thermocouple out at the side from in-between the roasting chamber and the heating chamber (the assembly into which the perforated cup fits). I am unsure whether the thermocouple segment within the chamber will withstand the heat but I suppose it should, since it's already intended to measure such high temperatures. By measuring the temperature at the middle point at the bottom of the roasting chamber, someone gets the highest possible temperature within, which is the sort of measurement I think someone would like to obtain. By allowing some time to pass, this temperature will inevitably propagate to the bean, but the bean could not get hotter than this (I suppose). If the operator is of the cautious type (has all the rules in his mind of the form: "don't get above XXX Fahrenheit/Celsius"), then this is the sort of measurement to look for (I am speculating). Plus, it's technically more practical to obtain this measurement in the case of a modified pop-corn popper than it to obtain the environmental temperature or the bean temperature, especially that the DC motor is not very powerful so that any obstacle, no matter how light within the chamber -such as the wire of a thermocouple, can very easily lead into a dramatic effect on the ability of the beans to circulate correctly (which is very true in my case, where the maximum airflow is barely good enough at the drying stage -where the green beans are still dense).

Best of luck.

Orwa.

On the last points: re: thermo couple segment withstanding and the "gets in the way" of bean circulation. I have experienced both...the thermo couple covering seemed to "shred a bit" turns brown and strings come vertically apart. the coupler does get in the way a bit; I had to hold it into the chamber.

I found that stirring or the act of aggravated stirring keeps things going and on par v. passively watching.

I have a Variac and could possibly mirror a modified system, but I prefer the manufacturer as is and use a long extension cord to lower the voltage here in the US...it slows things down...I have had some success with a modified temperature coupler on the Multimeter very similar to the one you show in the picture...but not doing a minute by minute look via a laptop program or anything.

It's fun to a least "know" what is going on...from that perspective.

I was wondering about that gap and Chaff...

As for the fan, I wonder if a BIGGER FAN within would perform a better job?

Right now I use a 120V AC FAN under the chimney to boost things and lower the temp a bit during the roast...

All put into a single surge protector power strip and then the wall socket - I get about 113-115V AC into the thing and it seems to work well.

I did notice as some have pointed out...these things, the popper/ery are not made for what we are doing and after 9 months of roasting - about 3 batches, small a month, mine is starting to thermal shutdown 3 min. at a time into the roast...could be the heat outside...maybe it's as my local roaster said; eventually the heating element and popper will "break." due to the use I am putting it through.

It goes on.

The answer to the ?'s help...

I though am still a bit concerned with altering the Popper/ery from stock...I would like to know how you progress with the new design as it relates to your roast and profiles...does it make and difference and how?

Also, did you fuse any of the circuit or but a breaker in for safety sake?

John

The roaster doesn't seem to be working properly. There is something wrong with the perforated roasting chamber. The holes made into the sides of roasting chamber are pointed downward rather than pointing upward, which could be good for popcorn (i.e. to push the seeds continuously against the very hot bottom of the chamber) but definitely isn't what is best for coffee. I had a very interesting observation today when the I started hearing a crackling sound different than that of the cracks, followed by a collective scattering of very small circles. By examining these funny microscopic circles I noticed that they had the surface of the bean on one side and an unclean layer of charcoal on the other. This seemed to be indicative of something wrong, especially that it happened at a time when the beans at the surface were relatively at a low temperature (way below 400 degrees Fahrenheit). My humble explanation is that the beans at the bottom were continuously being pushed against the very hot bottom of the roasting chamber rather than getting exchanged with those at the top. This also explains a number of other funny observations, one of these is the beginning of the second crack while the beans at the top were still at 400-405 degrees Fahrenheit. Moreover, when the scattering happened the temperature of the beans at the top was actually falling (it was 383 degrees Fahrenheit at the point the amusing explosion happened!).

I think that a new chamber should be made (!), or the current one be modified somehow (!!).

I can very easily be mistaken, but this is what I currently think. So, regarding my progress? not impressive at all . If someone thinks he has a clear idea as to what is going on in my case, explanations/suggestions are totally welcome.

Not an experienced air Roaster, but will try to help; till someone else does

Have you tried less beans? Start with very, very, little beans (30-40g?) and go up slowly till you find the max amount of beans your roaster can handle well. Can't think of much else.

Orwa,

As an extreme novice, I have seen those little circles - they are from the bottom. I think it's the thinnest shell of the bean and where it's stuck to the grate or vent at the bottom and yes, BURNED particles. By Stirring I have almost all but eliminated them.

The chamber does require, in my estimation with help from JIM S. and others, a smaller DOSE of raw bean v. say taking the amount of the Popper recommended if one was making popcorn.

I have found that these things can and do become incinerators very quickly once the bean start going...I contrary to what I have been told, STALL the roast - either by unplugging and monitoring temp. for FALL or the thermal cutoff kicks in and stalls for me...that's how I am at 10 min roasts now.

Try a very small batch of say: 2-3 tablespoons of beans; this will allow a lot of action in the churning of the roast.

An alternative I have found is to use either a long thin wooden dowel or a few sets of wood chop sticks connected at the wide part and stir, stir, and stir some more.

I try to cut the roast at the beginning of the second crack or right at it and then stir with vigor....until the smoke and steam stop...

I then dump into a nice copper core stainless steel POT and swirl it until the beans cool, then move it from stove burner to burner to cool the bottom of the POT.

Heat sink...

I try to roast lately when the AC voltage is lower and lowest at 115V or less...the extra fans help a lot - just directing them under the popper and at the body itself...

I think it's roast mass that is driving the particles and circle that looked burned....I watch and notice that if ONE does not stir a roast and keep it artificially moving v. the passive Popper fan swirling...things get stuck in one place and burn or brown quicker than other parts.

My local roaster seems to get a great chuckle - laugh out of the whole thing...he showed me a gas fired custom roaster and his drum turns with a rotissory type attachment within that keeps the beans moving...

Try a small roast and then a lot of swirling.

I have found that the time to rest is key on the roast and great disappointment comes with quickly trying roasts that are not cooled and have not outgassed.

For what it's worth -

John...keep trying and note your observations until you find a workable roast then replicate.

It's really important that the beans be mixed rapidly during the roast. If you don't have enough air flow for them to tumble and take their turn from bottom to top of the roaster, than reduce the bean load or stir. As they roast and become lighter and bigger, they are easier to loft with the air. If they are only swirling and not tumbling from bottom to top, that's not good enough.

The temperatures right outside of those vents are much higher than what you see on your 'bean probe'. For experiment, try to locate a probe right in front of one to get an idea what you are heating the beans with.

Now that you have control on the roaster, what should you do with those controls and when in the roast should you adjust? For starts, I would suggest to pace about 3 minutes for the beans to reach 300F, another 3-4 minutes to reach first crack, and then another 3-4 minutes to finish the roast at your desired degree. That should get you in range.

I don't have anything to add to the advice above, except to say
that when I was roasting with a popper I experienced exactly
the same vigorous shower of little pieces shooting off. At that
time, I thought it was amusing, but soon discovered otherwise.

It might be useful to know that these pieces are often called
"divots" -- that should help with searching for more information.

Thanks for your detailed descriptions and updates -- a very
useful resource to come back to.