Today's Message Index:
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1. 05:20 AM - Re: Integration of Rotax 912iS (user9253)
2. 06:14 AM - Re: Re: Integration of Rotax 912iS (C&K)
3. 07:59 AM - Re: Integration of Rotax 912iS (Eric Page)
4. 10:40 AM - Re: Integration of Rotax 912iS (user9253)
Message 1
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| Subject: | Re: Integration of Rotax 912iS |
It looks like the relay will be energized whenever the engine is running. If the
engine quits, you will turn on the backup switch. So the relay will still
be energized and depleting the battery that is needed to keep the engine running.
Or is my reasoning wrong?
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503416#503416
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| Subject: | Re: Integration of Rotax 912iS |
Figure 3.18: Wiring Powerside (optional)
in the install manual shows backup power bypassing the battery contactor
which seems like the preferred architecture to me.
Interestingly I recently had a battery contactor go high resistance. It
would run the panel and lights but instantly went open circuit when the
starter was engaged. Looked like new except the internal copper parts
had a black coating.
Ken
On 05/10/2021 8:19 AM, user9253 wrote:
>
> It looks like the relay will be energized whenever the engine is running. If
the engine quits, you will turn on the backup switch. So the relay will still
be energized and depleting the battery that is needed to keep the engine running.
Or is my reasoning wrong?
>
> --------
> Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=503416#503416
>
>
Message 3
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| Subject: | Re: Integration of Rotax 912iS |
user9253 wrote:
> It looks like the relay will be energized whenever the engine is running.
Correct. As long as the Backup Battery switch is open, the P-channel MOSFET is
turned on by the pull-down resistor on its gate, allowing current to flow through
the relay coil.
> If the engine quits, you will turn on the backup switch. So the relay will still
be energized and depleting the battery that is needed to keep the engine
running. Or is my reasoning wrong?
No, turning on the Backup Battery switch applies ~12V to the MOSFET gate, turning
it off, which stops current flow to the relay coil. I've confirmed that there's
no current path from pin X3-3 (normal power input) to pin X3-1, so there's
no voltage on pin X3-1 in normal operation.
HOWEVER... It turns out that pins X3-1 and X3-2 are shorted inside the Fuse Box,
which makes sense given that the Backup Battery and Start Power switches do
essentially the same thing. This means that closing the Start Power switch will
open my relay, which is definitely not the behavior I want.
Thanks for making me think this through, Joe. VERY helpful!
Eric
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503425#503425
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| Subject: | Re: Integration of Rotax 912iS |
There might be voltage on X3-1 when the engine is running if using EMS Ground as
the reference point. That should not disable the transistor which uses airframe
ground. Isolated grounds make it confusing.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503432#503432
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