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        Use a switch as a WOT control for big brushed motors

#1 WingMan33 Feb 19, 2004 05:21 PM

Use a switch as a WOT control for big brushed motors
 
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Hello I am replacing these with true controllers and thought I would post some pick of how to use a switch for brushed motor high amps 50 .simple cheap and glitch free, but you have to carry a reciver battery with this set up .

#2 WingMan33 Feb 19, 2004 05:22 PM

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you can see it size not to bad.

#3 SlowRider Feb 19, 2004 05:28 PM

Wingman,

Thanks for the info. What plane is that in the pics?


Andy

#4 WingMan33 Feb 19, 2004 06:02 PM

Slow rider A EL BEE. 48 inch Wing.

#5 Dax Feb 19, 2004 08:45 PM

so its all or nothing, WOT or dead stick.... might make for intresting landings :)

#6 zagisrule! Feb 19, 2004 09:54 PM

Geez! How much current are current will those microswitches take?









-Matt

#7 Fred Bronk Feb 19, 2004 10:39 PM

Not 50 amps continuous without melting!! :eek:

#8 Smokin' Beaver Feb 20, 2004 02:29 AM

I pulled some out of an old 3 phase instantaeous Hot Water System ages ago & they were rated at 25Amps AC @240 volts.
At under 12V, 30-50 Amps for short periods might work.
Phil

#9 zagisrule! Feb 20, 2004 08:16 AM

I think it would be a bit safer to just use some MOSFET's to switch the load....no, it is not very hard :)

All you need is a resistor per FET and a grounding resistor to ground for the whole group. You could then use your switch(even a very small one would work) to apply current to the bases and turn your motor ON.






-Matt

#10 Andy W Feb 20, 2004 08:32 AM

Remember, there are many folks in this hobby who do not know the first thing about basic electronics - this prohibits many exisiting wet-fuel modelers from trying electric. Some models even come with a wiring harness and a switch, and instuctions on how to connect this to a servo to turn on the motor!!
..a

#11 vintage1 Feb 20, 2004 10:31 AM

Just take a look at what your car starter motor takes to switch about 200A...and see how its dine.

IMHO the weight disadvantages of a mechanical switch outweigh the efficeincy loss on a MOSFET, and frankly, a brushed ESC is not much more expensive than a servo and a relaible switch, and receiver battery.

#12 BEC Feb 20, 2004 02:00 PM

Everything old is new again?? We used to do this sort of thing, many years ago before ESCs were as good as they are now (small, light, fairly inexpensive, good BECs and other features).

For 15 or 20A you can get away with a setup like that for some time. Sooner or later the switch will die. Been there, done that.

At 50A I'm surprised the switch doesn't weld itself together in the on position the first time you use it. A switch that's big enough to actually take that load and switch it safely (remember you WILL be switching the startup current of the motor) is large, heavy, and not cheap.

#13 Fred Bronk Feb 20, 2004 02:33 PM

"At 50A I'm surprised the switch doesn't weld itself together in the on position the first time you use it."

Get in, sit down and shut up, were going for a ride!!

I think we have stated our feelings about this very well. :D

#14 WingMan33 Feb 20, 2004 05:32 PM

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Wow a lot of Ideas Well it Handles 50 amps at 7.2 volts all day no problem it is rated at 5amps 250volts A.C. they bag a lot. as far as weight yes it is a disadvantage. it is cheap though 3bucks for the switch 14 for a micro servo. .Cheers

#15 rclark Feb 20, 2004 06:33 PM

Ummm, are you 'sure' your hitting 50 amps with that setup (measured) ???? That setup sure doesn't look like it will unless I am blind :) (could be I guess...) BTW just because you have a 50A ESC doesn't mean it will be pulling 50A. All it means is the ESC will 'handle' up to 50A.


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