Mail Archives: geda-user/2013/03/27/18:24:02
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You'd dissipate huge power in the coils trying to do it this way, I suspect.
Think of it more as an AC generator, you could use a full bridge
rectifier for three phase and a simple (albeit hefty) constant current
load, with a set point for the loading. Or if the analog CC load puts
you off, a big MOSFET to short the rectified output to provide load, PWM
drive this to vary the apparent load.
Either way, you have to get a good ratio to drive this, a few hundred
rpm will be a minimum.
Hope that helps,
Ed
On 27/03/2013 21:15, Rob Butts wrote:
>
> I got a stator and flywheel and my problem is that the stator has a 4
> wires coming from the stator and I don't have a schematic. There is a
> green wire which is screwed to ground. The rest, a yellow, a white and
> a red with blue stripped that all appear to go to different coils.
>
> I'm thinking these are three phases of an ac stator? My thought is to
> have the pedals spinning a shaft that the flywheel is tied to. Then
> I'd vary the votage going to each phase (dc voltage) which would
> produce a magnetic field and resistance to the pedaling.
>
> Any thoughts?
>
> Thanks,
>
> Rob
>
>
>
> On Tue, Mar 26, 2013 at 3:44 PM, Rob Butts <r DOT butts2 AT gmail DOT com
> <mailto:r DOT butts2 AT gmail DOT com>> wrote:
>
> I do understand how the magnetic field varies in the road bike
> trainer and kind of understand the eddy current braking theory. I
> did get an eight coil stator and flywheel that I thought I'd
> experiment with. In the see also section of the eddy current
> brake wiki page there is a link for Telma retarders and towards
> the bottom of that page a section describing an electric retarder
> which sounds exactly what I need and what I can use this $14
> stator and flywheel for. I think I just have to gear the speed of
> the flywheel as high as I can which at this point is 5 to 1.
>
>
> On Mon, Mar 25, 2013 at 10:13 AM, John Griessen
> <john AT ecosensory DOT com <mailto:john AT ecosensory DOT com>> wrote:
>
> On 03/24/2013 03:58 PM, Rob Butts wrote:
>
> One plastic disc is fixed and the opposing plastic disk is
> allowed to rotate 30 degrees providing the variable
> magnetic field and
> variable resistance. I have not been able to simulate the
> resistance I believe because I'm not providing the same
> rotational
> velocity of the aluminum disc.
>
>
> Sounds like the out of alignment of the discs makes the field
> vary from weak to strong.
> To have strong fields, each magnet needs to be straight
> across, (through the aluminum disc),
> from another with same polarity direction. Then induced
> currents flowing in circles around the strong field area
> counter subsequent motion by a force of their own. I've never
> quite grasped how that force stays local
> to any place in the aluminum plate though...perhaps inertia of
> electrons? Else moving the path of the high
> eddying current is more resistive than the eddy path? It's
> all so circular! I feel like researching
> and reading about it instead of doing my taxes...
>
> What do you mean by simulate? What velocity can you get?
>
> Some decent velocity is needed for small inexpensive magnets.
> I've seen a demo
> of eddy current braking done with a pendulum hung plate, then
> a slotted plate
> for comparison, where the opposing magnets were very massive
> and with iron looping
> around to make a complete magnetic circle path with two short
> gaps, ( where the aluminum
> plate moved). It would slow the pendulum in one stroke by
> 4/5ths. It must have weighed
> 80 lbs.
>
> An alternator will need velocity also. Bicycle gearing can
> get you velocity.
>
>
>
--
Ed Simmons
ed AT estechnical DOT co DOT uk
www.estechnical.co.uk
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<div class="moz-cite-prefix">You'd dissipate huge power in the coils
trying to do it this way, I suspect.<br>
<br>
Think of it more as an AC generator, you could use a full bridge
rectifier for three phase and a simple (albeit hefty) constant
current load, with a set point for the loading. Or if the analog
CC load puts you off, a big MOSFET to short the rectified output
to provide load, PWM drive this to vary the apparent load. <br>
<br>
Either way, you have to get a good ratio to drive this, a few
hundred rpm will be a minimum.<br>
<br>
Hope that helps,<br>
<br>
Ed<br>
<br>
On 27/03/2013 21:15, Rob Butts wrote:<br>
</div>
<blockquote
cite="mid:CALSZ9grq4mu78=xRroRPr7TM4Px_F5wByXZ28gPsiGf1E7+j=Q AT mail DOT gmail DOT com"
type="cite"><font face="Times New Roman" size="3">
</font>
<p><font size="3"><font face="Times New Roman">I got a stator and
flywheel and my problem is that the stator has a 4 wires
coming from the stator and I
don't have a schematic. There is a green wire which is
screwed to ground. The
rest, a yellow, a white and a red with blue stripped that
all appear to go to
different coils. </font></font></p>
<font face="Times New Roman" size="3">
</font>
<p><font size="3"><font face="Times New Roman">I'm
thinking these are three phases of an ac stator? My thought
is to have the pedals
spinning a shaft that the flywheel is tied to. Then I'd vary
the votage going
to each phase (dc voltage) which would produce a magnetic
field and resistance to the pedaling.</font></font></p>
<font face="Times New Roman" size="3">
</font>
<p><font size="3"><font face="Times New Roman">Any thoughts?</font></font></p>
<font face="Times New Roman" size="3">
</font>
<p><font size="3"><font face="Times New Roman">Thanks,</font></font></p>
<font face="Times New Roman" size="3">
</font>
<p><font size="3"><font face="Times New Roman">Rob</font></font></p>
<br>
<br>
<div class="gmail_quote">On Tue, Mar 26, 2013 at 3:44 PM, Rob
Butts <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:r DOT butts2 AT gmail DOT com" target="_blank">r DOT butts2 AT gmail DOT com</a>></span>
wrote:<br>
<blockquote style="margin:0px 0px 0px
0.8ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-left-width:1px;border-left-style:solid"
class="gmail_quote">I do understand how the magnetic field
varies in the road bike trainer and kind of understand the
eddy current braking theory. I did get an eight coil stator
and flywheel that I thought I'd experiment with. In the see
also section of the eddy current brake wiki page there is a
link for Telma retarders and towards the bottom of that page a
section describing an electric retarder which sounds exactly
what I need and what I can use this $14 stator and flywheel
for. I think I just have to gear the speed of the flywheel as
high as I can which at this point is 5 to 1.
<div class="HOEnZb">
<div class="h5"><br>
<br>
<div class="gmail_quote">On Mon, Mar 25, 2013 at 10:13 AM,
John Griessen <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:john AT ecosensory DOT com" target="_blank">john AT ecosensory DOT com</a>></span>
wrote:<br>
<blockquote style="margin:0px 0px 0px
0.8ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-left-width:1px;border-left-style:solid"
class="gmail_quote">
<div>On 03/24/2013 03:58 PM, Rob Butts wrote:<br>
<blockquote style="margin:0px 0px 0px
0.8ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-left-width:1px;border-left-style:solid"
class="gmail_quote">
One plastic disc is fixed and the opposing plastic
disk is allowed to rotate 30 degrees providing the
variable magnetic field and<br>
variable resistance. I have not been able to
simulate the resistance I believe because I'm not
providing the same rotational<br>
velocity of the aluminum disc.<br>
</blockquote>
<br>
</div>
Sounds like the out of alignment of the discs makes
the field vary from weak to strong.<br>
To have strong fields, each magnet needs to be
straight across, (through the aluminum disc),<br>
from another with same polarity direction. Then
induced currents flowing in circles around the strong
field area<br>
counter subsequent motion by a force of their own.
I've never quite grasped how that force stays local<br>
to any place in the aluminum plate though...perhaps
inertia of electrons? Else moving the path of the
high<br>
eddying current is more resistive than the eddy path?
It's all so circular! I feel like researching<br>
and reading about it instead of doing my taxes...<br>
<br>
What do you mean by simulate? What velocity can you
get?<br>
<br>
Some decent velocity is needed for small inexpensive
magnets. I've seen a demo<br>
of eddy current braking done with a pendulum hung
plate, then a slotted plate<br>
for comparison, where the opposing magnets were very
massive and with iron looping<br>
around to make a complete magnetic circle path with
two short gaps, ( where the aluminum<br>
plate moved). It would slow the pendulum in one
stroke by 4/5ths. It must have weighed<br>
80 lbs.<br>
<br>
An alternator will need velocity also. Bicycle
gearing can get you velocity.<br>
</blockquote>
</div>
<br>
</div>
</div>
</blockquote>
</div>
<br>
</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
Ed Simmons
<a class="moz-txt-link-abbreviated" href="mailto:ed AT estechnical DOT co DOT uk">ed AT estechnical DOT co DOT uk</a>
<a class="moz-txt-link-abbreviated" href="http://www.estechnical.co.uk">www.estechnical.co.uk</a></pre>
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