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Old Nov 12, 2012, 02:18 AM
jbarchuk is offline
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DeBary, FL
Joined Nov 2010
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brushed ESC control of fan/blower motor

Background. There's an interesting post about an electric plane flour-smoke generator at http://www.rcgroups.com/forums/showp...0&postcount=47 which even though it didn't work very well got me thinking. Its' main advantage is that it's not really a '$5.00 smoke generator' it's more like US0.14. LOL! The problem though is that it uses only the airplane's airspeed to force air coming in one hole to stir up the flour, and the low pressure of the 9 holes at the back end to draw the air out. Well there's not enough airspeed or turbulence to stir up the flour.

The turbulence thing. The main reason the above design doesn't work very well is that the flour just sits there and there's nothing to stir it up into suspension. So I'm thinking about what to do about -forcing- more air to make more turbulence and then also -push- the flour out. My intent is to add a tube that pokes down into the flour, and forced air 'bubbles up' through the flour and puts it into suspension.

I tried a tiny RS fan rated at only a few cfm, plus a 'neck-down' kind of venturi to make more speed, but it had no ability to create any pressure or turbulence and so failed.

So, how about at small air pump: http://www.skycraftsurplus.com/12vdc...gmairpump.aspx To save folks looking at that page it's 12V 300mA 2L/min 0.5lb. It's less cfm but it's a diaphram -pump- and has lots more -pressure- if not volume than the RS 'fan.'

If that doesn't work I'll try http://www.skycraftsurplus.com/dcfbb...Ifan12vdc.aspx That's still technically a fan but tons more cfm and more of a blower type assembly housing which means lots more pressure. It looks a lot like what I have for cooling fans in my laptop. That one is 0.68A and 23cfm 4.8oz.

In any case my Q here is how to power these devices.

I would like to use brushed ESC such as http://www.gravesrc.com/GPMM2005_GP_...p/gpmm2005.htm

I'm half hoping that running these 12V-rated devices won't turn them to toast at 12.6V of a fully charged 3s lipo. The alternative is 4s plus voltage regulator to get past the dropout. If I have to do that I'm not concerned about extra weight of another cell plus regulator because this is going into a Sig Kadet Senior with Hacker A60 and tons of extra thrust, but I'd still rather avoid the weight if possible and the annoyance of building more stuff.

The main reason I want to use ESC rather than simpler on/off control is that I can mix throttle to the blower speed / smoke volume.

And here's the -real- guts of my Q... The way I understand what I've been reading, I would:

- Disconnect ESC power wire where it plug into receiver.

- Connect battery power to ESC battery input. (3s, or 4s plus regulator.)

- Connect battery ground to ESC ground (which I'm guessing is internally commoned to the servo port ground.)

- Connect ESC + and - output leads to fan/blower.

I think that as long as whatever resistive device I attach is within the limits of the battery and ESC capabilities, and keep the auxiliary device +V away from the receiver/main battery/flight battery +Vs, I should be OK.

Actually if it comes to it I don't see any small-mA 4s batteries but I know how to connect 2 2s batteries in series.

Does it look like I have a clue about what I'm doing? Do I need to buy a vowel?

Yes I know the ESC is way overkill on the power load capability side of things but I'd really rather not deal with the time and annoyance of breadboarding this stuff.

TYVMIA

Jim
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