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allenb wrote:


greencardigan wrote:
Are you sure it's only 200mA? That sounds too low for 15V.

I agree. 2/10's of an amp seems low for a motor capable of lifting even a half a lb.

As far as a wiring diagram.

This circuit works real nice for up to 25 vdc and up to 3 amps. It uses a small rotary pot to dial voltage level. If using a transformer, use one with a secondary voltage not much higher than the motors max voltage. For a motor not drawing more than an amp the transformer would not be very large. As mentioned earlier, you can also use a dropping resistor.


Scroll to page 7 in the data sheet, top left of page. Use the LM350 not the LM150. Mount the LM350 to any sheet metal nearby for heat dissipation.


The secondary of the transformer or dropping resistor feeds the ac input to a bridge rectifier. The dc output of the rectifier feeds the input of the LM350.
Edited by allenb on 04/25/2011 8:40 PM
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
I have used a ceiling fan dimmer -> transformer -> rectifier to power a dc popper motor. This didn't require any soldering other than the inline fuse holder I used.


greencardigan wrote:
I have used a ceiling fan dimmer -> transformer -> rectifier to power a dc popper motor. This didn't require any soldering other than the inline fuse holder I used.

Cool, this is a whole lot simpler than my circuit and would be plug and play.

1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
It sounds like the variable setup would be a great way to try a few motors and find a winner. After that, a simpler setup could be determined.
The one motor I've got is unmarked , the 200ma 15vdc was the only numbers I saw on the wiring diagram.
Being able to try a few would be great.....
Allen, or GC,would either setup cover a wide enough range to test a variety of motors and find a potential winner?
- Scott
Both circuits have a lot and common, and should allow for experimenting with various motors.

Both need a transformer and a diode rectifier to step down the AC voltage to a low-voltage DC.

Allen's approach uses a circuit on the DC side to vary the final voltage. GC's approach uses an AC dimmer to vary the input to the transformer.

Be sure to get a transformer that can handle a 2 or 3 amps. Likewise the rectifier. While you can make your own with 4 diodes, the pre-built "full-wave bridge" rectifiers are inexpensive.
Ok, I think that can get me started at radio shack. Thanks folks. -Scott
Hard to say how much of a payload you'll be able to handle with a dc motor, so maybe start with a 3-amp, 24 volt RMS (secondary) tranny? with a *big* capacitor for filtering the output of the diode bridge, you might get near the peak voltage of 34 volts.
True ...if I can find one to move 1lb., I think it will be lucky. To make things worse, it's nearly impossible to order these motors as a replacement part. Those machines were never intended to be repaired! ......We'll see. -Scott
Heat Liner; For this I re-purposed a travel mug, but I think there are alot of viable options. Stainless steel water bottles and maybe even some containers from hairspray etc.
The curved top allows for something like a flange that the yoke nut can capture.
I selected one that left no more than 1/2" clearance between the heat element and the inner surface of the liner, all the way around. ....Anything smaller would not allow for tightening of the yoke nut.
JETROASTER attached the following image:

Edited by JETROASTER on 05/07/2011 9:46 AM
Although I have other things cooking, work continues on this unit as well. Both lids have the strainers knocked out, one will get a few more holes drilled.
JETROASTER attached the following image:

Edited by JETROASTER on 07/12/2011 4:36 PM
The bottoms have been removed from both vessels to accomodate the drain fittings. More happening soon! -Scott
JETROASTER attached the following image:

Edited by JETROASTER on 07/12/2011 4:39 PM
Ok...the projects are many, and time slips away.
Another person among us has expressed a willingness to move this thing forward.
So, before I pack up all the goodies for shipment...I'd been thinking of a small redesign.
I'd been considering changing the blower housing for something shorter and wider.... Picture an inverted mixing bowl.
This would allow for more space/cooling for controls. It would eliminate the need for an additional base, and perhaps most important; A 4" blower could be used.
The 3" blower is not so easy to source anymore.
Any un-needed airflow could be bled off, or used to enhance exhaust design (thanks to our Aussie friend,lmclaren)

The other option would be to flip the lower vessel upside-down...placing the blower in the widest section.

Ideas? -Scott
I vote for the wider base capable of housing a more standard vac motor.

In fact, I can envision an art-deco Waring blender looking base with the concentric ribs and slightly conical. Might be hard to pull that off.

1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
I'll find it! Also considering a diaphram actuated safety switch for the heat circuit. Once the blower is up to pressure, the heat circuit is completed. No heat.
Any other ideas are welcome. -Scott
Scott, I used a pressure switch as a safety interlock on one of the machines I built for work, too!
What kind of pressure range will they operate in? Toward the end of a roast cycle, The MH-1 is down to about 6.25" column pressure.
So the options are 1) find a pressure switch that will trip at a low pressure, and capable of carrying 18-19 amps, or 2) create a small mechanism that is actuated by the airflow, tripping a switch.
I better get shopping! ...I need to pack this project up.
Going out on the brown truck tomorrow;
1ea. of; 5' blower with gasket . Heat element(un-altered). lavatory drain(un-altered).
Wiring block.

2ea of; Jumbo cocktail shakers(pre-cut). Perf plate candidates(un-altered).

Plus a few stray parts that may or may not be useful.

The Flux Capacitor has been loosely pre-assembled, but inverted by comparison to the MH-1.
This allows usage of a 5" blower. Obviously too much air for this job, but chosen to allow for excess air dilution of the exhaust stream.

More goodies will be shipped soon, including a pressure gauge, a second lavatory drain (for the exhaust) sight glasses.

As it begins taking shape, I'll continue to support the building of the core 'heat-gun' as needed, but I'll hold off on some of the detail bits until we're sure they still fit the design.

Many thanks to Allen for taking this thing on!

Have Fun!! -Scott
JETROASTER attached the following image:

Edited by JETROASTER on 01/02/2012 6:39 PM
Looking forward to seeing the MH-1 and later the disassembled Flux Capacitor version and doing some roasting experimentation. I'm beefing up my universal PID control center wiring to handle the extra amps.

Looks like the MH-1 will arrive sometime on Friday.

1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
Scott I have a question how much room do you need for that motor to fit into.

4, 5 inches whats the diameter of it.

I pour Iron and roast Coffee BeansThumbsUp
If life seems normal your not going fast enough Mario Andrette
Hi David,
The motor that is shipping is 5" diameter and nearly the same height.( The MH-1 was a 3" dia .) The vessel max I.D. is 5.25", so it's a nice tidy fit
To accomodate, I inverted the entire lower vessel, putting the widest end at the bottom.
This puts the top of the blower very close to the element. Some of the nichr will be getting removed, so Allen might choose to shorten the whole element to get that radiant heat away from the blower.
If this blower turns out to be way too large, I'll send a 4".

Happy New Year! -Scott

Edit; Take 1/4" off those dimensions. The max I.D. of the vessel is just under 5", the blower is 4.75" diameter
Edited by JETROASTER on 01/04/2012 1:07 PM
I would , but it's not a finished product yet.
The first MH-1 build is on this thread;

That machine was sent to Allen for some testing and improvements.
If the platform proves to be worthy....then perhaps a second one will be built. That's why this thread was started.

Maybe part II will be a propane thing Grin
We'll see....... -Scott
Over the last 2+ months I've had the pleasure of hosting Scott's very cool MH-1 fluidbed roaster open source build project. As described in his thread ?Maximum Heatgun MH-1 HRO Edition? the goal is to put the roaster in the hands of HRO members for testing and possibly improving if deemed advantageous by the member and Scott.

I've run it through it's paces and performed various tests including control of rate of rise using variable airflow only and trying various charge weights. This roaster performs wonderfully and produces some excellent tasting coffee. I've only made minor alterations to the heating element chamber so far and there are opportunities for more improvements by the next member selected to carry on the project.

I'm requesting volunteers who would like to be the next host of the MH-1 to take it to the next level of improvements.

Preferred skill set:

-Experienced in coffee roasting
-Have previous experience with fluidbed roasters
-Good understanding of electricity and resistance wire convection heaters

Scott has supplied an ample quantity of green coffee for testing purposes which I will forward with the roaster so don't disqualify yourself due to not being able to afford a few pounds of green for experimentation. Although, you will probably want to roast some of your own stash once you see what this roaster is capable of.

If interested, please respond to this post or PM Scott for clarifications and questions.

Thanks Scott for allowing me the opportunity to be the first member besides yourself to test run this fine roaster!

Edited by allenb on 04/07/2012 1:18 PM
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
Oops, I edited this and saved changes only but somehow it moved it to the top. Honest, no bump intended!::trink25:
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
1.5" . It works out well for sourcing all the exhaust bits. Standard plumbing.
There is a link on post #5 of this thread. I bought one just a few weeks ago at "Target" for 19.99$
That's where I bought all the previous ones. Seems like a normal stock item. -Scott
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