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Homeroasters.org » BUILDING A ROASTER » Drum Roasters
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Copper door & lower hinges completed - 3/4 lb, heating element, drum type build log
rcwarship
seedlings wrote:
Try a batch preheated to 400F for 5 minutes before loading beans (if you can do that).

CHAD


Sounds like a winner to me Chad, I'll get the front of the roaster completed including door, sight glass & trier; then give the preheat a spin to see how it goes.

Thanks for your input, I appreciate it.

Best Regards To All,
Jon
Tell me and I forget, show me and I remember, involve me and I understand.
 
rcwarship
I am looking at a DC Motor/acme type thread combo for use as a dump mechanism to tilt the upper half of the roaster to dump the beans. I've never worked with varying speeds on a DC motor and am wondering how I could accomplish this. Any assistance from you electronic types would be greatly appreciated.

I have also thought that I could replace the shaft with a fine thread rod or a coarse thread to accomplish this goal if I can't get a DC motor speed control.

The unit description on http://www.surplu...m2888.html and their description is:

Motor assembly with a Buehler #1.61.046.531.00 Gearhead motor driving a 110mm (4-5/16") long lead screw. 85mm (3-1/4") Max travel, 4.3mm (1-11/16")/Rev. Plastic traveler with removable steel bracket. Approx. 105RPM/6VDC, 50 Slot Photo Tach. (5V powered) on rear motor shaft. Encoder output is TTL compatible with 50 pulses per revolution.

I would like to slow it down to something like 3 or so RPM (as a guess). I figure that 3 volts would get me around 53 RPM, which is still too high. So I'm wondering if there's a circuit out there that I can build (or buy) to accomplish this.

They also have a large assortment of glass, which I'll be ordering for the sight glass on the unit. Their shipping is real cheap at $5, so it's hard to go wrong.

Thank you in advance,
Jon
Tell me and I forget, show me and I remember, involve me and I understand.
 
Koffee Kosmo
Hi Jon

The product type that I am looking at for my roaster to adjust the speed of my agitator is this motor controller from Australia but you could source something closer to home if you could show them what you want

View the bi directional DC speed motor controller
http://www.oceanc...ollers.htm

This is what it looks like
www.oceancontrols.com.au/motor_controller/k166_tiny.jpg

KK
My web site > koffeekosmo.com.au I home roast and I like it :P
Blog - http://koffeekosm...gspot.com/
Bezzera Strega: BNZ MD74 Grinder: 5 Box hand grinders: Pullman Tamper Convex: (KKTO) Turbo Oven Home Roaster: CONA Glass Rod Syphon: Pyrex Brewer:
 
koffeekosmo.com.au
rcwarship
Thanks for the information KK, I have a kit on ebay on it's way....... http://cgi.ebay.c...1|294%3A50
Also, ordered the DC motor/gear combo and some round glass from the surplus site.
I spent 4 hours today trying to bend a thin walled aluminum tube 45 degrees without kinking it. I didn't have enough steel shot or any sand to pack in it, so I've got it in the freezer right now filled with water. If this doesn't work, I'll have to think of another way to get the beans from the funnel to the roaster. I will be looking at building a box on the face of the roaster and have the beans dump into it.
Woohoo, toooooooo much fun.
Best regards to all,
Jon
Tell me and I forget, show me and I remember, involve me and I understand.
 
rcwarship
Koffee Kosmo wrote:
Hi Jon

The product type that I am looking at for my roaster to adjust the speed of my agitator is this motor controller from Australia but you could source something closer to home if you could show them what you want

View the bi directional DC speed motor controller
http://www.oceanc...ollers.htm

This is what it looks like
www.oceancontrols.com.au/motor_controller/k166_tiny.jpg

KK


Heya KK,
I got to wondering about why a bi-directional controller? I got to thinking about it & decided to go with a single directional one and a double pole - double throw switch in the output. I fired off a question to the guy who has the kit on Ebay & he responded that there would be no issues. I also did a little research by way of google, got positive answers and a caution not to throw the motor in reverse when it's rotating. Just a thought.
Thanks again,
Jon
Tell me and I forget, show me and I remember, involve me and I understand.
 
Brainiac
Hi Jon

I used a double-pole center-off switch to reverse the (DC motor) drum rotation for bean dump on my roaster. This means that while the wiring is the same as a standard DPDT switch, the inherent delay in the transition means that there aren't too many issues with back-emf and such... (also gives built-in motor on/off, of course)

FWIW

Brian
 
rcwarship
Thanks Brian,
Brilliant, double pole center off it is. I see that there are momentary contact ones with spring return to center (off), which would be ideal for this application. Got some coming from Ebay.
Thanks Again,
Jon

PS Ice filled tubing doesn't bend, it does snap the aluminum very cleanly though.

Sand purchase next with heat on the joint is the next trial. It has to work this time, because I'm running out of tube.

Roflmao
Tell me and I forget, show me and I remember, involve me and I understand.
 
boom
Hey Jon

I use a lot of motor control in my project. You can use any of www.Microchip.com's pics, like the PIC18F886 or the easier route is to go with a pic that has a library written for it, like the one I'm using (dsPIC30F4011). For that, you'll need to know your way around electronics. Otherwise, a simple PWM (pulse width modulation) chip should do the trick.

PWM varies the output voltage you get from a microchip, although you'll need to ramp up the volts and amps with an h-bridge. This is where it gets difficult. An h-bridge is a transistor configuration that allows you to reverse the direction of a motor. I can send you the circuit diagrams if you want, but this is for precise motor control. I'm sure you can make an easier plan. Try getting a variac...the same stuff many guys use to adjust the temperature on a popcorn popper. They're expensive, but will allow you to vary the voltage turning a simple knob.

Just remember that, if you want to turn a DC motor at very slow speeds, you'll be drawing a lot of current. Since the torque is very high when the motor is just starting to turn, it draws a huge amount of current to get the motor going. After that, the current drops and you're in the green. I'd suggest starting the motor off at full speed to get over the initial torque, and then reducing your voltage to get to the slower speed.

Neil
A good espresso should give you hair on your chest!

Nuova Simonelli Mac Cup S, Mazzer Super Jolly, 1962 Faema President 2-group Lever, 1960 Faema Urania Grinder, 2kg profile controlled roaster
 
rcwarship
Neil,
Thank you very much for posting the link to your electronics, I had wondered where folks had gotten that kind of equipment.
I studied it, but unfortunately as you indicated a background in electronics would be important.

May I ask you a question?
Do you think a determined man of average intelligence would be able to figure out how to use the dsPIC30F4011? I would have the internet for research, and also members of this forum like yourself (if you have the time and inclination) for assistance. I enjoy learning & it looks like it would be a challenge for sure. Thanks in advance for your opinion.

I appreciate your input on DC motor current draw and a great layman's explanation of PWM, very helpful.

Best Regards To All,
Jon
Edited by rcwarship on 07/24/2009 11:55
Tell me and I forget, show me and I remember, involve me and I understand.
 
dBndbit
One possibility for a simple motor driver is a "power pack" from model railroad hobby shops. They're nearly perfect manual digital drivers ready to plug in the wall. And fairly cheap. Trouble is they're usually 12-15 volts output. Digital drivers are high-efficiency pulsed outputs at the rated voltage. Speed control is by varying the pulse width (PWM). They're fantastic for low speed control, but would be risky for using on lower voltage motors. You would have to add a filter capacitor to integrate out the high pulse levels to a lower average DC drive.

This part of your discussion sounds mighty complicated. I have to ask: Are you sure you wouldn't do better with just a tilt-handle?
Edited by dBndbit on 07/24/2009 18:07
Jim
11 years old... forever!
ReeferDoor.com
>home-built roasters and fair trade
 
http://www.ReeferDoor.com
seedlings
Does a DC motor vary speed with voltage? If so, here's a variable voltage regulator circuit that you can modify, depending on current, with beefier components.

i206.photobucket.com/albums/bb54/seedlings/VoltageRegulatorpinout.jpg

R2 sets the low limit.
"B+" is tube-talk for DC voltage.

You won't be able to speed it up, but you can slow it down.

CHAD
Don't put the cart before the horse. Put the horse in the cart and listen to him say "weeeee" all the way down the hill.
 
boom
HA! I found it. You're lloking for the Adriuno ( http://en.wikiped...ki/Arduino ). It's a simple, easy to program and cheap little microcontroller that will be perfect for someone to learn with. There are mounds of support for it, since it is a Google initiative. Should also be loads of fun to play around with. I use a similar chip, only a lotmore powerfull. But you don't need that. Get the controller and I'll hook you up with the h-bridge schematics. You'll need a pc, the Adriuno chip, an electronics supplier and a soldering iron...

As far as I know, the only way to drive a high current dc motor (like a car's wiper motors) is with an h-bridge or a push-pull circuit. An h-bridge is almost just a push-pull x 2. Here's the basics of transistors:

A transistor is a simple switch, which opens up as soon as the correct current is supplied to the gate. It has 3 pins, namely the gate, source and drain. Current flows from the source to the drain if sufficient current is applied to the gate. In other words, put 10mA (depending on transistor specs) on the gate pin and a connection will open between the source and drain pins. Mosfet drivers work almost the same as a transistor, but requires eg. 5V on the gate instead of 5mA and will generally allow you to take more amps.

The wiper motors I used easily drew 10A at startup (due to the inertia and static friction), so you'll need a decent circuit to handle those amps. Even your wires needs to be thick enough. So I would suggest either going all out electronic and build a PWM circuit (or microchip) and an h-bridge, or buying a Variac and controlling it by hand. A Variac is a transformer with a big knob on it. Turning the knob changes the ratio of primary vs. secondary windings in the transformer, allowing you to vary the voltage going to a dc motor. They can also take a whole lot of amps (i think), so it might be your best bet.
Edited by seedlings on 07/27/2009 12:14
A good espresso should give you hair on your chest!

Nuova Simonelli Mac Cup S, Mazzer Super Jolly, 1962 Faema President 2-group Lever, 1960 Faema Urania Grinder, 2kg profile controlled roaster
 
bvwelch
As a 'software dude' for the past 30 years, I'm always eager to encourage folks to give software and programming a try for themselves. But honestly, I'm not sure I'd choose coffee roasting as a first project-- instead, I'd recommend some of the 'Make' or 'Instructable' projects -- blink lights, make sounds, have fun, but don't try and control a process that involves lethal voltages, currents, and objects whirling around at 450 degrees F. Just my two cents worth. -bill
Edited by bvwelch on 07/25/2009 11:51
 
boom
I agree Bill, and I think the Adriuno is perfect for that. Lots of online resources to start out with, but the Atmel chip gives you just enough rope to hang yourself with.
A good espresso should give you hair on your chest!

Nuova Simonelli Mac Cup S, Mazzer Super Jolly, 1962 Faema President 2-group Lever, 1960 Faema Urania Grinder, 2kg profile controlled roaster
 
dBndbit
Atmel is better than Microchip!
Jim
11 years old... forever!
ReeferDoor.com
>home-built roasters and fair trade
 
http://www.ReeferDoor.com
rcwarship
Jim, Chad, Boom, Bill, I thank each of you for the information. I love this site, because of folks like yourself who are willing to share.

Jim, regarding: "I have to ask: Are you sure you wouldn't do better with just a tilt-handle?" Absolutely!!!!!!! But that would be like buying my coffee already roasted!!! Roflmao


Chad, is there a part number for the transistor? I believe the other components are pretty self explanatory, but I don't know enough to determine which transistor would be needed.

I am especially pleased to find out about Adruino (Thanks Boom), it looks like a fascinating learning project that will keep on giving. I've worked for years on mechanical stuff, wiring, metal, welding, lathes, milling machines, cabinets, plumbing, cars, trucks, etc . Lately, Ive been working on computers, and have taken some programming classes. However, I never took the opportunity to learn about microcontrollers. I'll be giving this some serious studying in the coming days to see how it goes. I appreciate your taking the time to dig up the data & links and posting the info.

Bill, "lethal voltages" hah, I laugh at danger (& other such silly phrases). Seriously, this looks like excellent fun.


Again, thank you all very much for your thoughtful replies, I am in your debt.
Jon
Tell me and I forget, show me and I remember, involve me and I understand.
 
boom
I wish I had the milling and welding skills!! They would have saved me thousands on my project and enables you to make anything!! I applied for a welding course, but later discovered that it's actually a course for convicts!! Rather not!

It sounds really stupid, but when you hook up your newly built electronic circuit board to some LED's and see them flicker, it's the coolest feeling ever! Even more so if those LED's controls your coffee roaster!
A good espresso should give you hair on your chest!

Nuova Simonelli Mac Cup S, Mazzer Super Jolly, 1962 Faema President 2-group Lever, 1960 Faema Urania Grinder, 2kg profile controlled roaster
 
rcwarship
LOL, you probably would have learned a lot from the cons. Thanks again for the updates, I'm working now, but have tomorrow & the day after off. I'll be researching on the microcontrollers. Great stuff.
Jon
Tell me and I forget, show me and I remember, involve me and I understand.
 
seedlings
I used a 9N90C salvaged from a bad PC power supply. A NTE2377 also works fine.

http://www.fairch...C_F109.pdf

But any N-channel MOSFET with enough specs (amperage) for your application will work. Insulate between the back tab and your chassis or heatsink. Use high-power resistors for R1 and R2.

R2 is 10% of the 1M pot, so your minimum voltage will be roughly 10% of the supply voltage. If you want the minimum higher or lower, adjust R2.

CHAD
Don't put the cart before the horse. Put the horse in the cart and listen to him say "weeeee" all the way down the hill.
 
rcwarship
seedlings wrote:
I used a 9N90C salvaged from a bad PC power supply. A NTE2377 also works fine.

http://www.fairch...C_F109.pdf

But any N-channel MOSFET with enough specs (amperage) for your application will work. Insulate between the back tab and your chassis or heatsink. Use high-power resistors for R1 and R2.

R2 is 10% of the 1M pot, so your minimum voltage will be roughly 10% of the supply voltage. If you want the minimum higher or lower, adjust R2.

CHAD


Absolutely fabulous!!! Chad, thank you very much for taking the time to explain how to source & size the components & especially for the explanations of how it works (previous post) and how to vary output.

I had looked through your photo gallery earlier & saw your picture of the way you mounted a CPU cooler to the MOSFET. I've got a bunch of those lying around & some thermal contact goober, so life is good.

I had not realized that these small items could carry 9 Amps, I am 52 and had always thought that they could only handle milliAmps. Now that you provided the spec sheet, I got to thinking cordless drills, circular saws, etc. They would all have large power requirements and of course the electronics would support them.

My linear motion assembly & glass is supposed to arrive today, so the fun continues!!!!!!!!!

Thanks Again,
Jon
Tell me and I forget, show me and I remember, involve me and I understand.
 
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