Today's Message Index:
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1. 09:28 AM - Re: Integration of Rotax 912iS (Eric Page)
2. 10:26 AM - Re: Integration of Rotax 912iS (user9253)
3. 06:06 PM - Re: Integration of Rotax 912iS (Eric Page)
4. 07:03 PM - Re: Integration of Rotax 912iS (Eric Page)
5. 07:19 PM - Re: Integration of Rotax 912iS (user9253)
Message 1
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| Subject: | Re: Integration of Rotax 912iS |
Tundra10 wrote:
> 1) There is a 22AWG powering the endurance bus feed relay coil, direct from the
battery, but not marked *. Perhaps add a fuse?
That wire (and the one on the Airframe Bud Feed Relay) will be about an inch long,
just jumping between two pins of the relay. I've marked them with a *.
> 2) There does not appear to be a power feed to the relay coil of the airframe
bus feed relay.
Oops! Good catch. Fixed.
> 3) Perhaps add an indication of the start relay engaged, in case it sticks?
Good idea. That signal can be fed to a general purpose input on the Dynon EMS-221
for display on the EFIS. I've added that to the diagram.
> 4) Perhaps add a 15A fuse at the battery bus to the endurance bus feed (14AWG
not marked with *).
> 5) Perhaps add a 15A fuse at the battery bus to the airframe bus feed (14AWG
not marked with *).
Those 14AWG bus feeders are protected by 18AWG fusible links at the Battery Bus.
That's one of my questions: is this an appropriate use of fusible links?
> 6) I didn't find the backup battery anywhere, but perhaps it is fed from the
Rotax fuse box?
"Backup Battery" is the inelegant name that Rotax uses for the switch that provides
power from the Battery Bus to the ECU, via the Fuse Box, in the event that
both internal alternator/regulator systems fail. The electrical system has
only one battery.
> 7) I dislike inline fuses. There are two inline 1A fuses. Why not make just include
them in the fuse box for the battery bus?
Funny you should mention that, as I don't like them either. They're very difficult
to service, but I couldn't immediately think of a better solution. Unless
one of the experts here tells me that I'm abusing the purpose of fusible links,
the Battery Bus will be a stud block like this...
https://www.ebay.com/itm/151830064157
...to connect multiple ring terminals. Perhaps a small 4-position ATC fuse block
like this...
https://www.ebay.com/itm/314111877309
...mounted next to the Battery Bus would be a better option for those fuses. If
I am abusing fusible links, then the whole Battery Bus can be a fuse block.
> Nicely done diagram. Easy to follow with lots of good notes.
Thanks, Jeff! I appreciate you taking a look.
An updated diagram is attached to this post.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=508069#508069
Attachments:
http://forums.matronics.com//files/electrical_architecture__kitfox_5__rotax_912is__v2_209.pdf
Message 2
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| Subject: | Re: Integration of Rotax 912iS |
Eric,
I admire your ability to design your own over-voltage protection circuit. Can it
be designed to just open the relay without blowing a 1 amp fuse?
Your Skyview must not have a backup battery since there is a brownout booster.
Is the autopilot switch momentary in both directions, center off?
Airframe bus shed:
I believe that one of the 3 relays inside of the Rotax fuse box is used for that
function. No external control is necessary.
> Those 14AWG bus feeders are protected by 18AWG fusible links at the Battery Bus.
That's one of my questions: is this an appropriate use of fusible links?
Yes it is. Having fuses in series is not a good idea, even if they are different
sizes.
Big Mistake:
Regulator "B" ground lug should NOT be grounded to the airframe.
When running, the Rotax iS engine has an isolated ground.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=508070#508070
Attachments:
http://forums.matronics.com//files/rotax_912is_schematic_445.png
Message 3
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| Subject: | Re: Integration of Rotax 912iS |
user9253 wrote:
> I admire your ability to design your own over-voltage protection circuit. Can
it be designed to just open the relay without blowing a 1 amp fuse?
Oops, that's another mistake. I meant to power that module through a resettable
circuit breaker instead of an inaccessible fuse. I believe that's Bob's recommendation
anyway.
> Your Skyview must not have a backup battery since there is a brownout booster.
Correct. I don't want the expense or maintenance burden of a backup battery.
All I care about is keeping the EFIS alive during engine starts. It's a VFR-only
airplane.
> Is the autopilot switch momentary in both directions, center off?
Yes. That little circuit is lifted directly from one of Bob's designs: http://www.aeroelectric.com/Reference_Docs/Misc_Pdf/AP_Disconnect_B.pdf
> Airframe bus shed:
> I believe that one of the 3 relays inside of the Rotax fuse box is used for that
function. No external control is necessary.
Well, sort of. If the B alternator fails or is switched to engine duty to replace
a failed A alternator, the Fuse Box will cut power to the rest of the ship.
However, since the Airframe Bus can get electrons from the battery, the Fuse
Box switching won't cut it off.
>
> > That's one of my questions: is this an appropriate use of fusible links?
> Yes it is. Having fuses in series is not a good idea, even if they are different
sizes.
Excellent, thanks.
> Big Mistake:
> Regulator "B" ground lug should NOT be grounded to the airframe.
> When running, the Rotax iS engine has an isolated ground.
I think you might have the A & B regulators mixed up. The engine normally runs
on the A regulator. The Rotax diagram shows the "Regulator A Plate" tied to
"EMS Ground" and the "Regulator B Plate" tied to "Airframe Ground."
> Suggest that the battery bus and airframe bus be combined into one bus called
the MAIN BUS. Eliminate the relay. Replace the 12 position fuse block with
a 20 position.
I thought about that, but I designed the Airframe Bus to power everything that
I don't need to continue flight to a safe landing. By separating the buses, I
can maintain the Backup Battery function and feed the Endurance Bus, but I'm
able to shed all unnecessary items by throwing one switch.
> Two switches can be reduced to one. See attached picture.
Yeah, that would definitely work. From a human factors perspective (simplicity
and reduction of confusion), I'd prefer to keep the Backup Battery and Start
Power functions separate. Switches are cheap, and the odds of both failing on
the same flight are about nil.
Thank you, Joe!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=508072#508072
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| Subject: | Re: Integration of Rotax 912iS |
Diagram updated as follows:
- Added annotation describing two 30A fuses at Battery Bus (Littelfuse MIDI 498
bolt-mount).
- Removed 1A inline fuse to EMS voltage sense pin and replaced with 24AWG fusible
link and 20AWG wire.
- Removed 1A inline fuse to OVP Module and replaced with 24AWG fusible link and
20AWG wire to panel-mounted 1A circuit breaker, then 22AWG wire to OVP Module.
- Added OVER VOLT TRIP circuit breaker to switch panel depiction.
Posting this time without 2nd and 3rd pages to reduce file size.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=508073#508073
Attachments:
http://forums.matronics.com//files/electrical_architecture_rev_j_aec_181.pdf
Message 5
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| Subject: | Re: Integration of Rotax 912iS |
> I think you might have the A & B regulators mixed up. The engine normally runs
on the A regulator. The Rotax diagram shows the "Regulator A Plate" tied to
"EMS Ground" and the "Regulator B Plate" tied to "Airframe Ground."
OOPS, my Big Mistake. You are right.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=508074#508074
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