Today's Message Index:
----------------------
1. 08:18 AM - Re: Booster coil (HBaker)
2. 09:06 AM - Re: Tachometer (HBaker)
3. 09:49 AM - Re: Re: Tachometer (Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E)
Message 1
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| Subject: | Re: Booster coil |
Hi Mark
A picture is worth a thousand words!
Henry
--------
Currently building a Murphy Moose - any help would be appreciated.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=280362#280362
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Hi Mark
I have a electronics guy hooking up the Horizons tack that I purchased last year,
We were going to wire it into the avionics switch, to be turned on after we
have started the engine and have switched to mags, because he heard the booster
coil is hard on the micro-processor . any thoughts on this??
Henry
--------
Currently building a Murphy Moose - any help would be appreciated.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=280371#280371
Message 3
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I have no personal experience with problems in this regard. As in...
Booster coil energy damaging the Tach. No one that I know of who has
installed this Tach has EVER had this problem. But, he may know
something I do not! Who knows?
Keep this in mind if you will.
The electrical path of the energy supplied by the booster coil for
starting, follows a completely different path than the energy that comes
from the mag AFTER starting. This is important to understand, so let's
continue.
The very only things that are used during starting in the mag are:
1. A retarded rotor point that makes contact with the BOOST COIL energy
through a slip ring.
2. The mag cap, where the spark plug wires actually connect.
THAT IS IT! Nothing else in the mag is used during starting except for
the mechanical parts that make the thing rotate when the engine turns.
With a good system, you can actually start and run the engine with the
starting circuit alone. I am not recommending that you DO this,
although I have for testing purposes.
There is a very brief period of time during starting where the starter
button is pushed, the engine has started on the booster coil energy
firing the spark plugs, the mags are turned on (P LEADS BECOME
UN-GROUNDED) and there is spark energy from both the mag itself (going
to a DIFFERENT contact point on the rotor) AND the boost coil retarded
rotor point.
So how is this going to impact the P leads and damage a Horizon Tach? I
don't see any way that it could, except for one thing, shielding. More
on that in a moment.
Also, there is no electrical "surge" in these aircraft because there is
no collapsing inductive magnetic field pulse from an electrical starter.
But now we come to shielding.
If you have bad shielding in ANYTHING... That means Booster Coil High
Voltage, it is ....in theory .....possible that it could get into the
main 28 VDC power source and cause damage to any kind of Avionics.
That said, let's go in a different direction for a second. The Horizon
Tach hooks to the P leads. The P leads contain a TON of RF noise from
the mags. That is why they are shielded. However, the actual P leads
themselves... BOTH OF THEM... Run into this Tach. It is entirely
possible for this noise energy to go into the Tach, and come back out on
the main 28 volt wiring that POWERS this Tach. Now you have this crap
getting into everything. Especially if you connect these wires to the
exact same circuits that are powering your RADIOS.
I am not saying this will happen. The engineers who designed this TACH
just HAD to take great efforts to try and prevent this. But I am saying
that more than one person has had significant noise problems when using
a Horizon Tach, and most ESPECIALLY with Becker Radios. Not ALL mind
you, but some.
So, my thoughts are that if you are going to hook it up this way, it
would be wise to put an RF noise filter on the power leads to the
Horizon Tach. Not to keep outside stuff from getting into the Horizon,
but to keep stuff in the Horizon from getting out and onto main aircraft
power wiring.
This can be as simple as using a torroidal core with the power wires
wrapped through them several times. Can't find one of those? Go look
around for an old computer monitor. Not the flat screen type, the old
big ones with a CRT. Look at the cables going to it. One of them will
have a big BULGE in the cable. Chop this off and carefully slice it
apart. Inside you will find a torroidal core with the wires wrapped
through it. They put it there for the same reason I am suggesting
putting it on the Horizon Tach power leads. You can also wrap the P
leads through one too.
Mark
-----Original Message-----
From: owner-m14pengines-list-server@matronics.com
[mailto:owner-m14pengines-list-server@matronics.com] On Behalf Of HBaker
Sent: Wednesday, January 06, 2010 12:06 PM
Subject: M14PEngines-List: Re: Tachometer
--> <henry.baker@nf.sympatico.ca>
Hi Mark
I have a electronics guy hooking up the Horizons tack that I purchased
last year, We were going to wire it into the avionics switch, to be
turned on after we have started the engine and have switched to mags,
because he heard the booster coil is hard on the micro-processor . any
thoughts on this??
Henry
--------
Currently building a Murphy Moose - any help would be appreciated.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=280371#280371
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