Re: (ET) Solid state controls

["goodguyforsure" <goodguyforsure hotmail com>]

Independent rear wheel braking: I am very interested in trying this. I am
planning a simple go cart method of a wide metal bar rubbing the tire. If
that works and gives me the turning that I want, I would proceed to use 
some
simple go-cart disc brakes on each hub. Does this bring any ideas?
John Briese
----- Original Message -----
From: "SteveS" <ssawtelle fcc net>
To: <elec-trak cosmos phy tufts edu>
Sent: Tuesday, July 23, 2002 4:23 PM
Subject: Re: (ET) Solid state controls


> I'm enjoying this thread, learning lots.
>
> Why would the E15 system be cheaper? On the E15 you are reversing heavy
> current loads, wouldn't the solenoids for that be much more expensive 
> than
> the relatively lightweight (though more complex)E12 relay?
>
> SteveS
>
>
>
> ----- Original Message -----
> From: "Christopher Zach" <czach computer org>
> To: "Pieter Litchfield" <plitch attglobal net>; <>
> Sent: Tuesday, July 23, 2002 4:38 PM
> Subject: Re: (ET) Solid state controls
>
>
> > Yeah, the E15 does things differently than the E20. On the E20, they
> reverse
> > the armature current using a pair of push-pull solenoids. On the E15,
they
> > reverse the field current using a DPDT relay.
> >
> > The problem is when you go from fwd to reverse in the E15, the back-emf
> from
> > the armature surges the contacts and burns the daylights out of them.
When
> > you go from fwd to reverse on the E20, the arc is absorbed by the (much
> > larger) solenoid breakers. Plus the field current is relatively weak
> anyway.
> >
> > But the E15 design is a lot less expensive; I guess that's why they
> migrated
> > to it.
> >
> > Chris
> >
> > ----- Original Message -----
> > From: "Pieter Litchfield" <plitch attglobal net>
> > To: <elec-trak cosmos phy tufts edu>
> > Sent: Tuesday, July 23, 2002 4:06 PM
> > Subject: RE: (ET) Solid state controls
> >
> >
> > > As the owner of the E-15 with bucket loader that loves to eat relays,
my
> > > suggestion would be that whatever controller is designed, be sure it
can
> > > withstand the abuse hard use will heap on it.  For example, my
tendency
> to
> > > rapidly shift from reverse to forward while using the bucket has had
> dire
> > > consequences for my relays.  A better design could improve on this
> > behavior,
> > > or at least prevent the idiot behind the wheel from making the quick
> shift
> > > ( a timer or charge-up delay circuit?)
> > >
> > > As a gross observation, my E-12 while not as elegant a control design
> > seems
> > > far more robust than the E-15.  At least I haven't cooked relays 
> > > there
> > yet.
> > > But this does suggest that a prime characteristic of a power control
> > system
> > > for an E-15 ought to be "robust-ness" and "fault tolerance."
> > >
> > >  -----Original Message-----
> > > From: owner-elec-trak cosmos phy tufts edu
> > > [mailto:owner-elec-trak cosmos phy tufts edu]On Behalf Of Bob Murcek
> > > Sent: Tuesday, July 23, 2002 2:11 PM
> > > To: elec-trak cosmos phy tufts edu; ssawtelle fcc net
> > > Subject: Re: (ET) Solid state controls
> > >
> > >
> > >   Steve,
> > >   No, reducing speed with a soild-state controller does not cause 
> > > loss
> of
> > > torque.  On an E12 at least the 1st and 2nd "speeds" are created by
> adding
> > > resistors in series with the armature circuit.  When the armature
> current
> > > tries to increase, say to go up a hill, the voltage drop across the
> > > resistors increases, causing the motor to slow down.  Since the power
> lost
> > > in the resistors is wasted, resistor-based speeds should only be used
to
> > get
> > > going smoothly.
> > >
> > >   Solid-state controllers turn the power in the armature circuit on
and
> > off
> > > rapidly (not sure of the rate, but it's apparently supersonic in
mine),
> > > varying the ratio of the on time to the off time to control the
average
> > > voltage seen by the motor.  There's very little waste since the
> > solid-state
> > > switch is either on or off.  When you go uphill with a solid-state
> > > controller and the armature current tries to increase, it's free to 
> > > do
> so
> > > during the times when the controller is in the on state, so a 
> > > slowdown
> > > doesn't occur.
> > >
> > >   Possibly the biggest advantage of a solid-state control in an ET is
> the
> > > extremely fine and smooth control at very low speeds, like when 
> > > taking
> up
> > a
> > > load or parking in a tight spot...Bob
> > >
> > >
> > >   >>> "SteveS" <ssawtelle fcc net> 7/23/2002 1:39:55 PM >>>
> > >   Ah, good explanation. I see now how it makes sense on an ICD mower.
> With
> > > my
> > >   E12S, with 'only' 3 speeds forward X 4 gears, I still have pretty
much
> > all
> > >   the control I need. I do find, however, that any speed less than
full
> > >   throttle has poor power. I can climb a hill in full throttle that
> stalls
> > > out
> > >   on lower settings (same gear). That seemed illogical at first, but 
> > > I
> > > assume
> > >   it's because the motor has less than full armature current. Does 
> > > the
> E20
> > >   have the same characteristic?
> > >
> > >   I presume a solid state control would have the same effect (lower
> > settings
> > >   for slower speed sacrifice power as well)?
> > >
> > >   SteveS
> > >   E12S
> > >
> > >
> > >   ----- Original Message -----
> > >   From: "Christopher Zach" <czach computer org>
> > >   To: "SteveS" <ssawtelle fcc net>; "Elec-trak" <>
> > >   Sent: Tuesday, July 23, 2002 12:49 PM
> > >   Subject: Re: (ET) Solid state controls
> > >
> > >
> > >   > Hydrostatics are nice on an ICE based mower because you usually
have
> > to
> > >   run
> > >   > the engine at full speed in order to keep the blades spinning.
> > >
> > >
> > >   -- snip snip snip
> > >
> > >
> > >
> > >
> >
> >
>