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allenb
02/02/2023 4:22 PM
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Low Cost Presto PopLite and Chaff Collector Mods
ChicagoJohn

Quote

turtle wrote:

Looks like your persistence and attention to detail as won out.

Been following your trials and tribulations on this build and look forward to hearing that all is as you expect it to be for your next roast!


I did two this morning and tried them without the resting period. Both were great -- a Kenya AA and a Guatamala.

What I find interesting is that I've been struggling with trying to get decent roasts from a Colombian and a Brazilian and so I switched to the Kenya and Guatamala to see if that would solve the problem.

The problem in all these was a burnt bitter undertone making them barely drinkable. Well, it turns out, I now believe, this was coming from uneven over-roasting at the bottom of the roasting chamber due to ineffective circulation and mixing of the beans.

Today's roasts were great! Back to normal !! None of that burnt flavor. Roasted to 1C and 20% after without exceeding 203C. Now I'll go back to the Columbia and Brazil and see what happens with them. I'm anticipating a substantial improvement.

It all comes down to the visual inspection of the beans' motion to make sure they are literally being thrown up into the air at a 91 gm charge, not just moving around a little. I was missing this visual in using the PCC chaff collector.

The funnel not only serves to increase the angle of repose to 60 degrees, it also greatly increases the effective air pressure at the base of the roasting chamber due to the reduction in area of air entry.

Now that I have the root cause identified and corrected, I'll know what to check for in the initial air flow with the green beans before installing the PCC and applying heat.

I'll follow this up tomorrow with my results with the Columbia and Brazil samples.
So many beans; so little time....
 
ChicagoJohn

Quote


I'll follow this up tomorrow with my results with the Columbia and Brazil samples.


Yesterday I roasted the Columbian and Brazilian dry process, both from Sweet Maria's, using my standard profile - about 7 minutes to 1C with 2 minutes for development at under 5C/min rate of rise after 1C.

Interestingly 1C was the same for both as before the air flow fix (195C and 202C, respectively). I believe this is due to the placement of my thermocouples which is in the bottom third of the been charge where movement was occurring even though it was greatly reduced on the top layer prior to identification and remediation of the leakage at the contact surface between the funnel and the blower base.

The blower was now capable of creating a "geyser" at highest speed (20.5VDC), occasionally tossing beans out the top of the popper chamber. By the end of each roast, it was capable of a few beans out the top of a 4.5 inch can acting as a chimney. Now the newer unit performs just like the first one I built using a 91 gm charge quantity.

While the strong "cocoa" undertone was now absent in the Brazilian and it was noticeably sweeter and less bitter, same for the Columbian, and in general, to my personal, novice taste there was less objectionable taste and aroma, I much prefer the Kenya AA and Ethiopian Yirga Cheffe samples I've tried because, to me, they seem to have a "fruitier" component I like -- a broader range.

Anyway, the main point is the blower issue is fixed for the 2nd build. I will continue to roast with this unit and will report any additional issues I discover and resolutions. In any development project that deviates from well-established technology unexpected problems are to be expected. Sometimes problem solving can be inefficient and circuitous, and for me that's part of the fun, especially when things finally work in terms of the intended objectives.
So many beans; so little time....
 
ChicagoJohn
Continuing to experiment, I decided to use some heftier rectifier diodes I picked up for $0.18 each to replace the puny ones that came with the popper. The reference on Amazon was from Amico 10 Pcs Molded Plastic Case 1000V 10A Rectifier Diodes 10A10 Price: 1.83 & FREE Shipping for 10.

I put the new bridge on a phenolic project board along with the heat-sinked 12VDC regulator, and while I was at it I decide to attach a 4700 uF 35V electrolytic capacitor I happened to have, about the calculated size needed for a 2 amp current at this voltage to significantly reduce pulse magnitude, noting polarity of course with respect to the DC +/- out from the bridge.

This brought the operating voltage at the blower up from 20.5 to 22.5 VDC on my Fluke meter, about a 20% increase in power (V^2/R), and there was a distinct change in pitch (rpm) and a significant improvement in bean action at all dimmer settings during roasting.

I plan to run it this way, alternating back and forth with my first unit which has no capacitor but does have a beefed up 10A bridge, and see if I discover any issues with motor life etc as a result of the power increase using the capacitor.
So many beans; so little time....
 
allenb

Quote

The funnel not only serves to increase the angle of repose to 60 degrees, it also greatly increases the effective air pressure at the base of the roasting chamber due to the reduction in area of air entry.


Are you still seeing the improved results with bean circulation? I remember many a complaint from others about this issue and I think your remedy will be of interest to other popper users.

Quote

This brought the operating voltage at the blower up from 20.5 to 22.5 VDC on my Fluke meter, about a 20% increase in power (V^2/R), and there was a distinct change in pitch (rpm) and a significant improvement in bean action at all dimmer settings during roasting.


Great way to get all the potential out of the rectified source. Many have been puzzled when they see a higher DC voltage compared to the AC source.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
ChicagoJohn

Quote

allenb wrote:

Are you still seeing the improved results with bean circulation? I remember many a complaint from others about this issue and I think your remedy will be of interest to other popper users.


As you know, I built two units. There was never an issue with bean movement in the first one. I made some changes in the second build, and I have seen variable performance in terms of bean movement in it and have been testing various hypotheses to see if I can produce more consistent and robust results in that unit.

Quote

This brought the operating voltage at the blower up from 20.5 to 22.5 VDC on my Fluke meter, about a 20% increase in power (V^2/R), and there was a distinct change in pitch (rpm) and a significant improvement in bean action at all dimmer settings during roasting.


Quote

Great way to get all the potential out of the rectified source. Many have been puzzled when they see a higher DC voltage compared to the AC source.

Allen


I did a roast yesterday of some yirga cheffe that went flawlessly. We will see if this continues. I may still decide to install another funnel to get a better fit with the chamber base without gasketing, and another concern is the 24VAC transformer I selected for the 2nd build for cost reduction purposes. My concern is that it may over heat and lose efficiency as this circuit is pushing the 40VA capacity. The first build used a Honeywell 40VA transformer which was definitely better quality and 80% higher cost. I am going to measure case temperature increase on both during a similar roast.

Maybe I just got lucky in building the first one because there has never been any issues with it. I'm sure that eventually I'll be able to report similar consistency in performance in the second unit.

Then we'll see how long each one lasts. :) In the mean time, I'm drinking some of the best coffee every morning I've ever had.
So many beans; so little time....
 
ChicagoJohn
I attached a K-thermocouple to the case of the Packard PF42440 and ran two batches. After the first batch, the case temperature was 140F and after the second it was 170F. This is approaching the maximum case temperature which I would imagine to be in the range of 180F or below. The fan mounted on the control box moves a fair amount of air over the transformer and out the exhaust holes (shown on the attached image), but the heat capacity of all the copper in the coils far surpasses the surface cooling, and after shutting off the fan and blower at the end of a batch, the case temperature rises another 5 - 8 degrees F.

I did the same exercise with my other unit using a Honeywell AT140A, also a 40VA transformer, and its case reached only 100F after the first batch and 125F after the second batch.

Despite the stated ratings, I would guess the Honeywell unit has more overpower margin built into the design based upon the temperature differences.

On the other hand, with the 470uF capacitor, the newer unit ran around 21-22VDC whereas the original unit ran 18.5 - 20VDC. So the actual power for the original unit might have been in the 45 watt range whereas it would have been closer to the 50 watt range for the newer unit.

I also fabricated a new funnel making sure to get the opening diameter right at 28.3mm. I did a sloppy job initially on the new unit and it would up at 33.5mm and didn't fit properly. The change in the funnel made all the difference in bean action especially in conjunction with the elevated voltage. The result for the newer unit in terms of fluidization of the charge is now even better than for the original unit.

So what I am going to do is to install a beefier transformer, the Honeywell AT150A which is rated at 50VA in the newer box. I'm going to leave the AT140A in the original but I'm probably going to add a capacitor and re-do the funnel in that one so I can make it fit as perfectly as possible. Now that I've experience the improved fluidization in the newer unit, I want to bring the original one up to the same level of performance. I'm convinced that this is an important factor in achieving a uniform roast.

Since I typically only do two 91 gm roasts at a time, I could probably stay with the Packard transformer, but while I'd do a 10% over draw, for another $18 I might as well upgrade it. I'm sure I can find another use for the 40VA transformer in the Arduino projects I've started on.

I'll update this forum entry as I acquire additional experience. The coffee has been great so far.
ChicagoJohn attached the following image:
current-build.jpg

So many beans; so little time....
 
ChicagoJohn
Someone advised me that what I really need is something called a "magnetic flux capacitor". Anyone know where I can get one? EBAY? I'm looking for one over 5F capacitance.
So many beans; so little time....
 
allenb
Wow, a 5 farad cap! Do they come with wheels for transport? I'll see if there's any that size in the museum in Colorado Springs. Let's see, a name for this roaster? The "Nikola Popper"

Good to hear the latest funnel attempt worked well for bean movement. We'll need some video action pretty soon!

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
ChicagoJohn

Quote

allenb wrote:

Wow, a 5 farad cap! Do they come with wheels for transport? I'll see if there's any that size in the museum in Colorado Springs. Let's see, a name for this roaster? The "Nikola Popper"

Good to hear the latest funnel attempt worked well for bean movement. We'll need some video action pretty soon!

Allen


5 mF: 5000 uF :) sorry about that, and thanks for the correction.

Can you tell me the criteria for posting video? I tried to take some flash photos but couldn't capture the action sufficiently. I'd love to post 3 second videos to show the fluidization of each unit. Would I put it in a zip file? Is there a way to post it directly as an .avi or .mov file?
So many beans; so little time....
 
allenb
I'm going to have to defer the non-youtube video upload question to our resident site gurus ginny and jack.

5 uF or 5000 uF sounds much better!

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
ChicagoJohn

Quote

allenb wrote:

I'm going to have to defer the non-youtube video upload question to our resident site gurus ginny and jack.

5 uF or 5000 uF sounds much better!

Allen


5 F would not be out of the question at low voltages, of course. But we are talking 35V in this case. 5mF / 5000 uF.

So you're suggesting that if I were to upload a video to You Tube I could then just give the link here?

I have an account on Flickr, and I think I could do it there also (the people who follow my photography would just figure I'd finally flipped out :)

I'll check out the You Tube option as I am on that but have never posted a video.
So many beans; so little time....
 
allenb
The only video uploading I've done has been with youtube vids. After you create one or pull one up on your youtube account, click the share tab just below it and copy the highlighted URL. Then, paste the URL into your HRO post, highlight it and then click the youtube icon in the toolbar just below the text box your writing in and when you hit the "post reply" button it should show up as a viewable youtube image within the post.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
ChicagoJohn

Quote

allenb wrote:

The only video uploading I've done has been with youtube vids. After you create one or pull one up on your youtube account, click the share tab just below it and copy the highlighted URL. Then, paste the URL into your HRO post, highlight it and then click the youtube icon in the toolbar just below the text box your writing in and when you hit the "post reply" button it should show up as a viewable youtube image within the post.

Allen


Thanks, Allen! I will follow your advice because that was one piece I was missing in the message of how it should look. I'll try go get this going in the next few days since I just got the new AT150A transformer and am trying to figure out how to fit it in the case. I think I have it figured out, thank God, because for a while I was afraid I might have to build it all over again in a larger case. But my guardian angel has saved me, I think. We'll see. Pictures and video to follow.
So many beans; so little time....
 
ChicagoJohn
This is how it looks with the Honeywell AT150A transformer installed. You can see that when oriented as shown, it fits within the space at the top. However, it was necessary to cut off the two metal case tabs at the top.

Per Allen's suggestion, I will look into making a You Tube video that covers this in detail and shows the degree of fluidization in the chamber at both 91 gm and 113.5 gm, 1/5 and 1/4 lb quantities, respectively. Having no prior experience with video photography, this may take a while, but I will do it at some point.

In the mean time, I'll post any further observations here.
ChicagoJohn attached the following image:
honeywell-at150a.jpg

So many beans; so little time....
 
JackH
Transformer is getting bigger John.

If you post a Youtube video use the Video tag. Insert the full Youtube link between the video /video.

An example:

[video]https://www.youtube.com/watch?v=Qlbb6yrM7aU[/video]
JackH attached the following image:
youtubevideo.jpg

---Jack

KKTO Roaster.
 
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