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- Newsgroups: rec.models.rc
- Path: sparky!uunet!panther!mothost!lmpsbbs!bobwo
- From: bobwo@ecs.comm.mot.com (Bob Woodhouse)
- Subject: Re: Help on motors and speed controllers
- Organization: secure_comm
- Date: Mon, 9 Nov 1992 18:27:38 GMT
- Message-ID: <1992Nov9.182738.1032@lmpsbbs.comm.mot.com>
- References: <92311.002649U40348@uicvm.uic.edu>
- Sender: news@lmpsbbs.comm.mot.com (Net News)
- Nntp-Posting-Host: 145.1.147.44
- Lines: 82
-
- In article <92311.002649U40348@uicvm.uic.edu> U40348@uicvm.uic.edu (Jay Lorenzana) writes:
- >Dear Netters:
- >
-
- I am no expert, so I will only answer those questions that I am reasonably
- confident about.
-
- >I am trying to drive a basic rc electric motor,
- >Kyosho 24 degree timing, 27 turn motor.
- >
- >First of all:
- >
- >Is this some kind of stepper motor?
-
- No, it is not really a stepper motor -- you cannot step it by applying
- various voltages to various contacts. I believe that if you require
- a stepper motor, you may wish to look elsewhere. Keep in mind that I barely
- know what a stepper motor is.
-
- >
- >How much countinous current can this motor take (aprox.)?
- >
-
- Oh, you can momentarily get maybe 80 amps or so, I guess. I would guess that
- with 'average' ventilation and so forth that you might get up to 20 amps, but
- at some point you might have the brushes wear out if you're talking about several
- minutes or more at this current.
-
- >What is the 24 degree timing specification?
- >
-
- It indicates an amount of rotation that the brush and brush hood (holder) are
- in advance of the magnet positions in the motor can, I think. If this is not exactly
- correct, it does at least reflect the right idea.
-
- >Do I have to be concerned with timing when designing
- >a speed controller?
-
- I doubt it. Of course, a motor with 24 deg timing will have neg 24 deg timing while
- in reverse, if this matters to you.
- >
- >I want to make someting SIMPLE, can I just use a variable
- >resistor for a speed controller? Note, effeciancy is NOT
- >important.
-
- It is simplest to go out and buy a $50 ESC. You can use a pot in-line with
- the battery/motor.
-
- >
- >Why are some speed controllers rated at 100+ amps continous?
- >I can't imagine an 8.4V Nicad package delivering this kind
- >of power. I can see that 100+ amps can be present when the
- >motor is turned on and off. What am I overlooking?
- >
- This is a long story. It means if the FETs are full on, they could pass 100
- amps. You need this number of FETs in the first place to handle the half-throttle
- condition where the FET spends a lot of switching time in a high-power dissapation
- mode. So the ESC doesn't need to pass 100 amps at full throttle, but it could.
-
- >What does freq. have to do with speed controllers? Do they
- >convert the 8.4vdc to xxx volt ac? Therefore, can I drive
- >this motor with a direct dc source or must I convert?
- >
-
- Rather than dropping power across a pot, the battery energy is pulsed to the motor
- at about 2500 Hz, where the width of the pulse is correlated to the throttle.
- >
- >Thanks for any help you can provide. I am in a strange
- >university contest and am supplied with this motor.
-
- Sorry for the ragged explanations, but full ones would try my patience at typing.
- >
- >-Jay
- > Univeristy of Illinois
- > at Chicago
- >
-
- Bob Woodhouse
- > Internet: U40348@uicvm.uic.edu
- > Bitnet : U40348@uicvm.bitnet
-
-
-