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allenb
09/21/2022 6:56 PM
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Choosing a blower
chris200071
Hello all - i am struggling finding a DC blower powerful enough for my 500g fluid bed roaster. I now use an AC blower rated at 600W and 98 CFM, which is WAY too powerful. If I twitch a couple of volts over 80v on the regulator then the beans paint the ceiling! I'm looking for a less powerful, but powerful enough blower so that my 'Matthius' CR3 board can handle it without changing the voltage regulator or risk damaging the board (that way I can regulate the fan through PWM on Artisan). Matthius recommended keeping the blower to 4A and the regulator is currently maxed out at 28V. I wonder if I could get some opinions from people regarding what I should be looking for in a blower, as I have now gone through a couple by mistakenly buying them based on high CFM/flow rate.

Apart from amperage/voltage and, therefore, wattage, what else is important when selecting a fan? There are a lot of affordable DC axial fans out there, designed for boat cooling and ventilation. But I bought a 12v 2.5A fan, rated at 130CFM and it was nowhere near powerful enough. Static pressure is something else I keep seeing, and it looks relevant to the application, but i'm not sure if it is. I'm learning quickly that flow rate pretty much means nothing in this context. So am I just looking for the highest wattage I can squeeze in? If that's the case, I could get a 24V 4A axial cooling fan (96W) and 3D print a reducer to fit it in my pipe and I'm away, but I'm worried about buying yet another fan not powerful enough to handle the load and wasting my money. Does fan design make a huge impact? Are inline fans inferior to other forms of fans?

Cheers, everyone for any wisdom you can share!
 
ChicagoJohn
Unless your AC blower uses an induction motor, you could use a PWM control to vary its speed. That's what I'm doing, and varying speed it can be useful in controlling the roasting profile. The voltage is constant with PWM and you are just varying the duty cycle from 0 to 100%, and it's pretty smooth and linear with respect to power whereas power varies with V^2. You can pick up a suitable PWM control for in the neighborhood of $10.
So many beans; so little time....
 
chris200071
Hi John, When you say PWM on AC, do you mean using zero cross detection so it can be powered from Artisan, or are you referring to using something to the equivalent of a voltage regulator but in PWM form to get better smoothness in regulation? The issue is I want automated control of the fan, rather than manual control. The voltage regulator works fine, although having a PWM regulator, where I could alter the duty cycle would be nicer, definitely. I also want a smaller and lighter (and quieter) fan. 600W is way more than I need. Could you post a source for your PWM controller?
Brew me up, Scottie!
 
mg512
I think he might mean something like this:

https://www.tindi...rod_search

It takes PWM as input and does the zero-detection itself. Basically makes an AC load PWM-dimmable.
Edited by JackH on 08/11/2018 6:08 AM
 
ChicagoJohn

Quote

chris200071 wrote:

Hi John, When you say PWM on AC, do you mean using zero cross detection so it can be powered from Artisan, or are you referring to using something to the equivalent of a voltage regulator but in PWM form to get better smoothness in regulation? The issue is I want automated control of the fan, rather than manual control. The voltage regulator works fine, although having a PWM regulator, where I could alter the duty cycle would be nicer, definitely. I also want a smaller and lighter (and quieter) fan. 600W is way more than I need. Could you post a source for your PWM controller?


The controls I use are like those in the attached photo. I use the one rated for 2000W for the blower motor (it will only actually handle about 800W continuous without active cooling). I'm using an AC motor from a vacuum cleaner that draws 580W at 100% duty cycle (power factor ~ 1). I use the one rated for 4000W to control the heating wattage. Mine will put out 2000W at 120VAC but I typically don't exceed 1600W.

Both are operated manually by a rotary control. In an earlier design, I did automate control of the heat to follow a prescribed profile using a stepper motor controlled by an Arduino, but I now control both air and heat manually and very few adjustments are needed to produce a repeatable profile. For the air, my RC design typically requires 500W to lift the bean mass initially, and I dial it back to around 420W after drying. (I'm using a charge weight of 340gm)

So if you'd consider controlling your blower manually, and you're using a brushed AC motor, not an induction motor, I think either of these would likely work. I got the ones I'm using on Amazon.
ChicagoJohn attached the following image:
pwm.jpg

Edited by ChicagoJohn on 08/11/2018 5:39 AM
So many beans; so little time....
 
renatoa
Indeed, this is an important point to emphasize: the motor type.
Induction don't like pwm ! their rotation speed must be controlled by frequency.
Which is which... ?
If you have them in hand, induction are those rotating freewheel, without no friction or resistance.
The PWM friendly motors are brushed, those making sparks when rotating Grin
 
chris200071
Cheers everyone - i am ideally looking for a DC motor for automatable control. I'll post the build on here when I'm done but I'm building a completely portable, fully-automated roaster to support my transient life of travel and new-found love for coffee roasting. My AC blower is large and heavy and I need a regulator to manage it. Most DC motors are smaller, quieter, lighter and more efficient; and, if I can find one to match the board, I won't need a regulator. I'm 3 fans in now and wasted my money on all three. I'm just not sure what figures I should care most about. I guess wattage? As that equals power which allows for rotation against pressure, but i'm not sure of the role of static pressure or CFM/M^3/m. I'm 5 days away from leaving Netherlands for Chile and I want to get the hardware finished before I leave. This is the missing piece.

Anyone here using a relatively low wattage DC motor successfully?
Brew me up, Scottie!
 
ChicagoJohn
FYI - Most AC motors that have brushes are universal motors in the sense they can be operated with AC or DC.
So many beans; so little time....
 
allenb

Quote

chris200071 wrote:

As that equals power which allows for rotation against pressure, but i'm not sure of the role of static pressure or CFM/M^3/m. I'm 5 days away from leaving Netherlands for Chile and I want to get the hardware finished before I leave. This is the missing piece.

Anyone here using a relatively low wattage DC motor successfully?


Something to consider when picking out a blower for use with a fluidbed roaster. For most designs, we need at least 10" of static pressure measured in inches of water column. As you stated, cfm is almost irrelevant since they require such a small flow rate to roast coffee in the 5 lb and below batch size roasters.

There's two commonly used blower designs that's available to us. 1. vacuum blower or vacuum motor (two different terms for the same item) which typically produces lots of static and well above what we require and typically less than 100 cfm. These motors run at very high rpms (15-25 thousand rpm). To produce high static pressure requires quite a bit of motor power which is why you see specs in the range of 400 to 700 watts listed. These are normally using a universal, AC/DC brushed motor in order to get the horsepower needed in a small package.

2. Centrifugal blower. In order to achieve the needed 10" and higher static pressure needed to lift a pile of beans in a fluidbed, the blower wheel diameter typically needs to be around 8" diameter or larger in order to sling the air fast enough to hit 10" + at typical induction and other style motor rpms of 3450 rpm. This is a large package due to the 8" or larger wheel diameter. Finding a brushed, DC or other type DC motor capable of variable speeds coupled with a centrifugal blower in the 8" or larger wheel diameter is not easy and would normally be an OEM item that's intended for a specific purpose on an existing piece of equipment and not an off the shelf offering.
Finding one will be a challenge and is why most of us default to the trusty AC/DC vacuum blower.

Axial fans, except for ones that run at 10,000 rpm or faster, normally will not be able to hit 10" or higher static pressure.

To hit high static pressure with any of these style blowers requires motors in the 400 + wattage ratings.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
chris200071
Wow, cheers, Allen! Excellent piece of information! So it's better to generally look for centrifugal blowers with a larger blower wheel diameter of 8" and above? That's what you're saying, in my context? And blower wheel here means fan/propeller size? Or do you mean something else? Otherwise, an axial fan that can hit 10,000rpm or faster within wattage limitations may be okay. But I imagine that would be quite noisy.
Brew me up, Scottie!
 
greencardigan
What about blowers from handheld DC vacuum cleaners?
 
renatoa
@greencardigan, go to the shop with a mock-up roast chamber made from a pet bottle and the desired quantity of greens you want to test. And also some duct tape ;)

https://www.youtu...QR8n0QKUS8

So you can check at the shelf if the blower is appropriate Grin
 
chris200071

Quote

ChicagoJohn wrote:

FYI - Most AC motors that have brushes are universal motors in the sense they can be operated with AC or DC.


That's really interesting - but surely voltage and current still dominate? So if its made for 220/230V (in europe), then it wouldn't be very successful running it on 12 or 24V DC?
Brew me up, Scottie!
 
renatoa
Rewound, why not...
 
ChicagoJohn

Quote

chris200071 wrote:

Quote

ChicagoJohn wrote:

FYI - Most AC motors that have brushes are universal motors in the sense they can be operated with AC or DC.


That's really interesting - but surely voltage and current still dominate? So if its made for 220/230V (in europe), then it wouldn't be very successful running it on 12 or 24V DC?


There are various ways to connect the DC supply. You connect it to the two brush boxes and also to the field coils, but you can connect them in serially or in parallel and get differing speed and torque results. You may want to google this (e.g., operating universal motors on AC and DC) and watch some tutorial videos on the subject. Good luck with your project and let us know how it's going.
So many beans; so little time....
 
allenb

Quote

chris200071 wrote:

So it's better to generally look for centrifugal blowers with a larger blower wheel diameter of 8" and above? That's what you're saying, in my context? And blower wheel here means fan/propeller size? Or do you mean something else? Otherwise, an axial fan that can hit 10,000rpm or faster within wattage limitations may be okay. But I imagine that would be quite noisy.


Ok, there's a little more going on with centrifugal blowers than just wheel diameter. In order to achieve static pressures this high at typical mid range rpms (3500), blower wheel width is necessarily fairly narrow in relation to wheel diameter. When shopping for a centrifugal blower for your roaster, you don't need to zero in on wheel diameter and width as this will end up being what it needs to be when you satisfy the requirement of X cfm at 10"+ static pressure. Otherwise, you'll be looking at page after page of blowers with 8" + wheel diameter and most will be low static pressure rated. Unfortunately, finding centrifugal blowers that meet our requirements is not an easy task and is why most end up grabbing a vacuum blower. Easy to find, relatively low cost and small package. Yes they're noisy but one can add a noise baffle around them as long as they can breathe to keep them cool.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
chris200071

Quote

There are various ways to connect the DC supply. You connect it to the two brush boxes and also to the field coils, but you can connect them in serially or in parallel and get differing speed and torque results. You may want to google this (e.g., operating universal motors on AC and DC) and watch some tutorial videos on the subject. Good luck with your project and let us know how it's going.


Thank you, John. It's very clear that I shouldn't rush into this and should learn more about it. The tight deadline I had given myself wasn't helping. I guess I'll use the AC blower for now and explore the options offered in this thread when I settle in Chile. Thanks for your input and help!
Brew me up, Scottie!
 
chris200071

Quote

Ok, there's a little more going on with centrifugal blowers than just wheel diameter. In order to achieve static pressures this high at typical mid range rpms (3500), blower wheel width is necessarily fairly narrow in relation to wheel diameter. When shopping for a centrifugal blower for your roaster, you don't need to zero in on wheel diameter and width as this will end up being what it needs to be when you satisfy the requirement of X cfm at 10"+ static pressure. Otherwise, you'll be looking at page after page of blowers with 8" + wheel diameter and most will be low static pressure rated. Unfortunately, finding centrifugal blowers that meet our requirements is not an easy task and is why most end up grabbing a vacuum blower. Easy to find, relatively low cost and small package. Yes they're noisy but one can add a noise baffle around them as long as they can breathe to keep them cool.


I am looking online and see several high static pressure DC centrifugal blowers from China for around $100, including drivers (not sure what the drivers are for). Unfortunately, here vacuum blowers are not that easy to find (i'm in the Netherlands now) - they are sold for specific vacs, so finding specs on them such as wattage and static pressure is nearly impossible, and they are crazy expensive (between 300-500 euros) and too high wattage (when you are able to find the specs). But i'll keep looking, cheers!
Brew me up, Scottie!
 
renatoa
You can buy a vacuum cleaner for a lot less and get the blower.
For example Hoover UltraMATT MBC500UV or similar stuff, from UK ebay.
 
chris200071

Quote

renatoa wrote:

You can buy a vacuum cleaner for a lot less and get the blower.
For example Hoover UltraMATT MBC500UV or similar stuff, from UK ebay.


Really good idea. I'll take a look. Cheers, mate!
Brew me up, Scottie!
 
renatoa
Just found the motor used in a broad range of 500W vacuum suckers, it is $20 as spare part in my country, you have below the specs and references to search in your country:

Motor Universal Aspirator 230V 50/60HZ 500W 34.500RPM.
Dimensiuni: Inaltime 130mm, Diametru: 140mm.
AEG Ardo Bosch Brandt Candy Electrolux Hoover LG Moulinex Nilfisc Philips Rowenta Samsung Siemens
Cross Reference: EAU61004901 VCC264E02 VC9205FS4 VK8914NHCQ,
Motor Assembly Vacuum Cleaner.

cdn1.shopmania.biz/files/s1/129500355/p/l/3/motor-aspirator-500w~8382923.jpg
 
chris200071

Quote

Just found the motor used in a broad range of 500W vacuum suckers, it is $20 as spare part in my country, you have below the specs and references to search in your country:
cheers mate, unless I am misunderstanding something (which I could be), that's an AC motor, and it's 500W, which is way over the 100W maximum the CR3 is setup to handle safely. Is there a way of using it in a way that doesn't end up in computer destruction yet automation?
Brew me up, Scottie!
 
renatoa
Yes, it's AC, but brushed, can be PWM controlled.

About 500W, check previous page allen post #9, to find why...
"Finding one will be a challenge and is why most of us default to the trusty AC/DC vacuum blower.
...
To hit high static pressure with any of these style blowers requires motors in the 400 + wattage ratings."
 
elkayem
Chris, I've been working on a fluid bed design and selected this 12V DC pump: https://www.airhe...-pump.html. It is advertised at 22A, 260 Watts, though I only measured 15A, 180W. In any case, it may be adequate for your needs. I just tried it with 500g and it had plenty of power for that, with rapid recirculation. Don't use the corrugated hose though, since (as I discovered), it cuts down on the air flow.
 
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