From: "David Roden (Akron OH USA)" <roden ald net>
To: elec-trak cosmos phy tufts edu
Subject: RE: (ET) RE: Alltrax DCX300 availability - Field current
Date: Thu, 27 Jan 2005 01:27:12 -0500
On 26 Jan 2005 at 15:33, john briese wrote:
> If I were doing it again, I would: 1) Install an inline fuse
> with the controler, which could be removed after successful install.
This is one of the changes I made to Steve's instructions - not without
spending a lot of time considering where the fuse should be located, and
what its effect might be if it opened. I didn't remove the fuse after a
successful installation though. I can't see any reason not to keep it
there
forever. I don't know how well it really protects the controller - too
often
silicon blows to protect the fuse <g> - but it's certainly better and safer
than
no fuse at all.
I put the fuse in the line which provides 36v for controller logic power,
and the
control voltage for the throttle and reverse switches. My old fuse panel
had
gotten pretty flaky anyway, so I just replaced it with one that had four
positions instead of three. I suppose one could fit an inline fuseholder
under
the instrument panel if that's easier.
I used a 7 amp instrumentation fuse. I'll probably replace it with
something
like 2 or 3 amps later, but 7 amps was what I had on hand.
I also connected the thermal breaker on the motor in series with the seat
switch and key switch, instead of in series with the armature, as Steve
suggested in the manual.
Finally, I retained the main disconnect (I think Steve junked his only
because
it was already broken). The typical failure mode for a transistor
controller is
full speed ahead. So even though there's a main contactor, I don't think
it's a
good idea to run without a redundant manual safety shutdown.
There are a few more things I still want to do as part of this upgrade when
the
weather warms up. One is a charging lockout. This may be a bit of a pain,
since I use three 12-volt chargers rather than the GE charger.
Another is a Sonalert or similar gadget that sounds when I get off the
tractor
but leave the key on, a bad habit that I have. I think I saw one of the
electronic seatbelt dingers (as used in cars) at one of the electronic
surplus
places once; that would be kind of cool.
The last and most important is a high pedal disable. This is a function
that
refuses to let the vehicle move if the accelerator pedal is already
depressed
when the key is turned on or the brake is released. It's standard on golf
car
and road EV controllers, and GE implemented it on the ET's original
controls.
I was surprised and disappointed to find that the high pedal disable on the
Alltrax ET controller is ... disabled! It's apparently included on their
golf car
controllers, and there's an option to enable it in the Alltrax software,
but
checking that option has no effect. The reason for omitting this feature
from
the ET version of the controller (at least the early one I have) is a
complete
mystery to me.
As a result, I can open the throttle pot all the way and turn on the key;
the
tractor will take off running. Or I can hit the brake while plowing; the
tractor
stops, but then when I release the brake the tractor starts right up again.
Some people will probably consider this a convenience, but I see it as a
hazard. So I plan to implement something externally, probably using the
potbox microswitch and an SCR or a small relay. (Suggestions welcome.)
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