Today's Message Index:
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1. 08:11 AM - Re: Re: Which Oil Pressure Switch? (Robert L. Nuckolls, III)
2. 04:38 PM - Overvoltage Protection for Rotax 9-Series Engines (Eric Page)
3. 06:50 PM - Re: Overvoltage Protection for Rotax 9-Series Engines (user9253)
Message 1
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| Subject: | Re: Which Oil Pressure Switch? |
At 04:30 PM 5/20/2023, you wrote:
>
>Thanks Bob.
>Sounds like your plan is exactly what I'm looking for. Not sure I
>fully understand what's going on though.
>You lost me at "I've sketched out an adapter circuit that would
>interface the square wave output of your
>tachometer pickup to the hour-meter." :) I can follow the diagrams basic
>wiring, but still need some time in a dark corner to figure out the rest.
>Slightly above my elctronical knowledge level.
>I would happily accept/appreciate whatever you could come up with out of
>your junkbox. Surely we can do some type of horse-trading to make it
>worth your while.
>Thanks again,
>Shawn
Very well sir. I'm mindful of the fact that
this forum is populated with a diversity
of experience and skills. It was not my wish
that you grasp the gritty details of my
proposal. But publishing the 'details'
affords opportunity for those interested
and willing to add the them to their
personal bag of tricks.
I'll scrape off a bit of space on the
workbench and hammer this thing together.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 2
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| Subject: | Overvoltage Protection for Rotax 9-Series Engines |
In a forum thread that I started in October 2021 about using a Rotax 912iS on my
Kitfox, there was some discussion about my use of crowbar overvoltage protection
(OVP). In that thread, Joe Gores asked, "Can it be designed to just open
the relay without blowing a 1 amp fuse?" It turns out that, yes, it can. After
several prototypes, I have a non-crowbar OVP Module for Rotax 9-series engines.
See the attached PDF document.
The oscilloscope screen capture shows its performance. Each horizontal division
is half a millisecond (0.0005 sec) and each vertical division is 10V. The yellow
trace is bus voltage (it starts at ~14.5V) and the purple trace is the output
driving the relay coils (this trace is inverted; the relays are closed when
the trace is at zero and open when it's above zero). When the bus voltage
jumps to 40V, there's a ~3 millisecond delay (a time lifted from Bob's design,
to prevent very short transients from causing nuisance trips), then the relay
coil drive drops out (purple trace rising). Once tripped, the module latches
in the tripped state, holding the relays open, which isolates the engine's stator
feed from the regulator input. The module also flashes an indicator LED
on the instrument panel and sends an alarm signal to an EFIS/EMS input. The
trip voltage is adjustable and is set at 16.3V (another value lifted from Bob's
design) but I used 40V for the test to demonstrate that the module can survive
an overvoltage event (it's designed to survive 60V).
The module adds pilot control of the charging system, a feature lacking in the
Rotax wiring diagrams. The 912/914 manuals specify a B-lead circuit breaker that
also feeds the regulator's Control terminal, but without a switch. On the
912iS/915iS engines, the regulators are exclusively controlled by the Rotax "Fuse
Box" and the only regulator terminals accessible to the installer are the
AC inputs. To provide pilot control, the module includes a latching PUSH ISOLATE
switch, allowing it to be held in the off state (e.g. in the event of smoke/fire)
or to be reset in the event of a nuisance trip.
I'd love to hear feedback on this design from anyone who cares to offer it. As
I've demonstrated repeatedly on this forum, I'm not an electrical engineer, so
I may have overlooked something.
Eric
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510846#510846
Attachments:
http://forums.matronics.com//files/ovp_module_oscilloscope_417.jpg
http://forums.matronics.com//files/ovp_module_rev_j_177.pdf
Message 3
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| Subject: | Re: Overvoltage Protection for Rotax 9-Series Engines |
Eric, your schematic is way over my head. Are you sure that you aren't an electronic
engineer. Good work.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510847#510847
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