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Popcorn maker motors
I've just modified a European (230V) popcorn maker for roasting coffee. From the (very useful) information available on this site I think it is a fairly typical design:
* Two heating elements, used as a potential divider to provide lower voltage to the fan motor;
* DC fed to the motor via four diodes as a rectifier.

I'm now controlling the heating using as solid-state relay so that I can change its output from software running on a Raspberry Pi computer. The motor is powered from a 30V/5A DC power supply (I've removed the diodes), and draws about 0.7A during operation. This is provides excellent control, and very successfully roasts small batches (around 50g) of green beans.

I'd now like to be able to roast larger batches, and the main limitation at the moment is the airflow from the fan - so I'm wondering whether it would be possible to swap the motor for a higher power version. I can see lots of different RS-385 motors online - does anyone have experience of what to look for in a replacement fan motor? Ideally I'd like to be able to get something powerful enough to circulate around 100g of beans in the popper.
Moded so far two models, a Zilan and a Silvercrest (Lidl brand)
At 24 volts the Zilan was been able to move 120 grams, and the Silvercrest 200 !
Check here a video from a happy Silvercrest owner, many didn't believed his numbers... Grin

Both machines initial factory voltage was in the 19V ballpark.
But the Silvercrest motor draws 2A when powered from the 24V source !
This could explain its "muscles".

So wondering what voltage are you using... I guess 30V should be reduced somewhat, not direct connection, else the motor should be toasted quickly...

Also, seems the turbine build is the secret of the various machines load capabilities, if they are all using a similar motor...
Interesting - I suspected there would be some variation between popcorn makers, but I had no idea that there is that much difference. Maybe I will just buy a different model and try that.

I didn't measure the voltage on mine before modifying it, but I think it was higher than 19V (the heating elements are 10 Ohm and 37 Ohm). I wasn't able to get decent airflow for coffee roasting until I cranked it all the way up to 30V.
Before giving up on your current popper you could try opening up the fins where the air flows into the roast chamber to see if that moves things better.
Alternatively, if your air intake allows it, supercharge - use a small shopvac as a blower to pressurize the plenum. Just a matter of getting a good seal.

FWIW - my tweaked Poppery1 does 150g w/o assistance or tilt .. supercharge ($20 shopvac) gave me ballistic ejection for 500g loads (limited by chamber size), unless I dialed back the drive to ~40%. Which gave me the requisite agitation, but not enough heat for the airflow. Best I could do with a supercharged Poppery1 was ~250g.
Edited by scotthal on 03/03/2019 4:47 PM
Food for thought; coffee for concentration
Or air pumps for inflatable pools/boats, in the 100W ballparks, these are used here by some fellow builders for up to 330 grams machines.
110 W, Bestway 62056 is the most popular, we buy here for $11.
Thanks for all the good ideas - will report back when I've had the chance to try something out.
So, thanks to the advice from renatoa, I am happy to report that I have sourced a Silvercrest popcorn maker on eBay and that it is truly excellent. I've tried it with 140g at 18V, which worked perfectly - all I need to do now is add a chimney to contain the coffee beans and I should be able to go nearer to 200g.

I tried modifying the vents on the old machine and this provided a small improvement, but the Silvercrest is in different league!
Is indeed a mystery what make this machine so potent compared to others...
Other than the turbine wheel, I can't see what could be different to create double airflow thrust, using a motor in same league as the others.
Hello again! After some good roasts in my Silvercrest machine I'm itching to try something else, and considering going down the supercharged route to get even better agitation of the beans at >200g batch sizes.

The question I have is this: does anyone have any experience regarding which type of popper air vent design is best when supercharging: the side fins or the bottom vent?

Up until now I have preferred the side fin design, which creates a circular motion in the beans. However ideally I'd like to get the beans moving in more of a 'fountain' once I have improved the airflow, which makes me think that a bottom vent might be more appropriate. What do you think?
The 7 cm dia of poppers is too small for such quantity, imo.
I suggest to check the attached image, that is an unfinished experiment, maybe give you ideas bring it to a functional level.
What you see it's the glass from one liter frenchpress, which is 9 cm diameter, and match perfectly the cylinder that hide the heater of a silvercrest. It is fixed with Alu adhesive tape, and a seal of red silicone on the bottom, that don't show in picture.
Yes, it's a silvercrest base what you see in the picture, with the tin roast chamber removed.
After removing that Alu cylinder, the hot air exhaust opening is covered by a kitchen sink sieve, having very good size holes and distribution. 2/3 of exhaust area is covered because the experiment was about asymmetric roast fountain.
From this stage you need to add the beans chute, at 45 degrees for beginning, and start experimenting.
LE: lost couple of minutes trying to attach picture, until I figured it has extension jpeg, which is not allowed... renamed as jpg and it worked. Silly... 3 chars extension heritage from the forgotten era of MS-DOS Grin
renatoa attached the following image:

Edited by renatoa on 08/28/2019 8:54 AM
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