Today's Message Index:
----------------------
1. 01:38 AM - Fuel Pump - dual switching (leckers)
2. 04:33 AM - Re: Fuel Pump - dual switching (Bruce Gray)
3. 06:49 AM - Fuel Pump - dual switching (ROGER & JEAN CURTIS)
4. 07:57 AM - Re: Fuel Pump - dual switching (Bill Bradburry)
5. 08:16 AM - Re: Peer Review of Schematic (rckol)
6. 11:09 AM - Re: Fuel Pump - dual switching (B Tomm)
7. 01:34 PM - Re: Fuel Pump - dual switching (ROGER & JEAN CURTIS)
8. 03:46 PM - Re: Peer Review of Schematic (user9253)
9. 04:31 PM - Re: Peer Review of Schematic (Noah)
10. 05:02 PM - Re: Peer Review of Schematic (Noah)
11. 05:14 PM - Re: Re: Peer Review of Schematic (Robert L. Nuckolls, III)
12. 05:18 PM - Re: Peer Review of Schematic (Noah)
13. 06:04 PM - Re: Peer Review of Schematic (user9253)
14. 08:06 PM - Re: Peer Review of Schematic (rckol)
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Subject: | Fuel Pump - dual switching |
I have the original panel mounted switch for the fuel pump on my Glasair - simple
'on/off'. On the copilot side I have the stock stick and only a single PTT
on the grip. On the pilot side, I have JD's Infinity grip with one of the switches
(at present it is a simple on/off) ear-marked to also operate the fuel pump.
I need to retain the panel switch capability so the copilot can operate the
pump if (s)he is flying.
My thoughts were along the lines of a switching system like the staircase example
of a switch at top and bottom being able to turn on or off the light from either
position. I would be quite happy to have a warning lamp to indicate the
pump is actually on/running. I need a different type of S700 switch (Which?) on
the panel, and also need to find a smaller equivalent type to fit in JD's grip
- both of which accomplish the necessary internal switching. (I definitely
need assistance with a simple wiring diagram too!). I don't see the necessity
for a relay set-up as I've used for the flaps with a similar scenario - normal
panel switch and JD's toggle switch on pilot's stick grip. I've been through
the chapter in Bob's book on switches a couple of times, but I can't find an applicable
example to help me on this - though it is, I have to say, that I may
be me missing the obvious - "can't see the wood for the trees" etc. etc.
This particular switching scenario must have been resolved many times before, and
I'd be most grateful if a member could point me in the right direction?
--------
IanL
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Subject: | Fuel Pump - dual switching |
Hi Ian,
Check a house wiring book.
Bruce
www.Glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
leckers
Sent: Saturday, April 10, 2010 4:35 AM
Subject: AeroElectric-List: Fuel Pump - dual switching
I have the original panel mounted switch for the fuel pump on my Glasair
- simple 'on/off'. On the copilot side I have the stock stick and only a
single PTT on the grip. On the pilot side, I have JD's Infinity grip
with one of the switches (at present it is a simple on/off) ear-marked
to also operate the fuel pump. I need to retain the panel switch
capability so the copilot can operate the pump if (s)he is flying.
My thoughts were along the lines of a switching system like the
staircase example of a switch at top and bottom being able to turn on or
off the light from either position. I would be quite happy to have a
warning lamp to indicate the pump is actually on/running. I need a
different type of S700 switch (Which?) on the panel, and also need to
find a smaller equivalent type to fit in JD's grip - both of which
accomplish the necessary internal switching. (I definitely need
assistance with a simple wiring diagram too!). I don't see the necessity
for a relay set-up as I've used for the flaps with a similar scenario -
normal panel switch and JD's toggle switch on pilot's stick grip. I've
been through the chapter in Bob's book on switches a couple of times,
but I can't find an applicable example to help me on this - though it
is, I have to say, that I may be me missing the obvious - "can't see the
wood for the trees" etc. etc.
This particular switching scenario must have been resolved many times
before, and I'd be most grateful if a member could point me in the right
direction?
--------
IanL
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=293734#293734
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Subject: | Fuel Pump - dual switching |
I have the original panel mounted switch for the fuel pump on my Glasair -
simple 'on/off'. On the copilot side I have the stock stick and only a
single PTT on the grip. On the pilot side, I have JD's Infinity grip with
one of the switches (at present it is a simple on/off) ear-marked to also
operate the fuel pump. I need to retain the panel switch capability so the
copilot can operate the pump if (s)he is flying.
IanL
Here is a simple circuit that requires using 2 single pole
double throw (on - on) switches. Hope this helps a bit.
Roger
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Subject: | Fuel Pump - dual switching |
IanL,
I doubt you will find a switch small enough to fit in JDs grip that will
carry the amps necessary for the fuel pump. If you already know how to do
this with a relay, I suggest you go ahead with that method. Or you can
stick a relay in the schematic that was provided by one of the readers.
Bill B
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of leckers
Sent: Saturday, April 10, 2010 4:35 AM
Subject: AeroElectric-List: Fuel Pump - dual switching
I have the original panel mounted switch for the fuel pump on my Glasair -
simple 'on/off'. On the copilot side I have the stock stick and only a
single PTT on the grip. On the pilot side, I have JD's Infinity grip with
one of the switches (at present it is a simple on/off) ear-marked to also
operate the fuel pump. I need to retain the panel switch capability so the
copilot can operate the pump if (s)he is flying.
My thoughts were along the lines of a switching system like the staircase
example of a switch at top and bottom being able to turn on or off the light
from either position. I would be quite happy to have a warning lamp to
indicate the pump is actually on/running. I need a different type of S700
switch (Which?) on the panel, and also need to find a smaller equivalent
type to fit in JD's grip - both of which accomplish the necessary internal
switching. (I definitely need assistance with a simple wiring diagram too!).
I don't see the necessity for a relay set-up as I've used for the flaps with
a similar scenario - normal panel switch and JD's toggle switch on pilot's
stick grip. I've been through the chapter in Bob's book on switches a couple
of times, but I can't find an applicable example to help me on this - though
it is, I have to say, that I may be me missing the obvious - "can't see the
wood for the trees" etc. etc.
This particular switching scenario must have been resolved many times
before, and I'd be most grateful if a member could point me in the right
direction?
--------
IanL
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=293734#293734
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Subject: | Re: Peer Review of Schematic |
Noah,
I don't see any wiring errors.
I am planning to use the same architecture but with a couple of different details
you might consider.
1. I am going to eliminate the two shunts and run both alternator B leads through
one Hall Effect transducer. This eliminates the need to add switching for
the shunts. The AFS manual that I have (about 2 years old) shows provisions for
only one shunt.
2. I am going to use an LR3C regulator instead of the SB1B. With the install kit,
the SB1B is $308 more than the LR3C and the I don't see that the extra features
it has add any value in this application.
You will have a main alt out annunciator light, plus voltage and current reading
on the AFS, plus you can probably program alarms for a low voltage condition
in the AFS, so the automatic turn on feature is not adding any value in my opinion.
You will also be able to read the voltage and standby alt current on the AFS, so
the blinking current warning light is also redundant.
Great features for adding to an old TC aircraft, but you already have their functions
well covered.
Just my 2 cents.
Dick Kaehler
--------
rck
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Subject: | Fuel Pump - dual switching |
While the schematic in the drawing will work, I wouldn't use that
architecture because it will be confusing. Sometimes switch toggle up will
be on and sometimes switch down will be on, depending on the position of the
other switch. That drawing is OK for light switches at home or for
pushbutton latching switches.
I would just wire both switches in parallel so that either one can turn the
pump on, but both must be off to turn pump off. I think this would be best
and satisfy 99% of your flying needs without confusion.
My $.02 worth.
Bevan
> _____________________________________________
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of ROGER
> & JEAN CURTIS
> Sent: Saturday, April 10, 2010 6:47 AM
> To: aeroelectric-list@matronics.com
> Subject: AeroElectric-List: Fuel Pump - dual switching
>
>
>
> I have the original panel mounted switch for the fuel pump on my Glasair -
> simple 'on/off'. On the copilot side I have the stock stick and only a
> single PTT on the grip. On the pilot side, I have JD's Infinity grip with
> one of the switches (at present it is a simple on/off) ear-marked to also
> operate the fuel pump. I need to retain the panel switch capability so the
> copilot can operate the pump if (s)he is flying.
> IanL
>
>
> Here is a simple circuit that requires using 2 single pole double
> throw (on - on) switches. Hope this helps a bit.
>
> Roger
>
> << File: Dual switch fuel pump.pdf >>
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Subject: | Fuel Pump - dual switching |
While the schematic in the drawing will work, I wouldn't use
that architecture because it will be confusing. Sometimes switch toggle up
will be on and sometimes switch down will be on, depending on the position
of the other switch.
When the light is on the pump is on, flip
either switch and it is off. I personally would not find this confusing.
If up, down is confusing, mount the switch for left, right.
I would just wire both switches in parallel so that either
one can turn the pump on, but both must be off to turn pump off. I think
this would be best and satisfy 99% of your flying needs without confusion.
If both switches are on they must both be
turned off to shut down the pump.
If you are going this route, might I suggest
that you put a switch on the panel within ease reach of either pilot, fewer
parts, fewer single points of failure.
There are other ways of accomplishing this,
but this is simple and will work.
Roger
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Subject: | Re: Peer Review of Schematic |
Noah,
Here are some suggestions for weight savings.
12AWG (or maybe 14) is big enough for the aux alternator and E-Bus.
Have you done a load analysis on the E-Bus, adding the actual amperage of individual
loads (not individual fuse sizes)?
The main power bus feed is not normally protected by a fuse. If you want to, that
is OK. But one ANL60 can protect both the alternator B lead and the main
power bus feed wire from excessive battery current. The alternator can not put
out much more than 60amps, so it is not necessary to use a fuse between the
alternator and main power bus.
6AWG is big enough for the main alternator unless you expect that the aircraft
load will continuously draw 60amps.
Joe
--------
Joe Gores
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Subject: | Re: Peer Review of Schematic |
rckol wrote:
> Noah,
>
> I don't see any wiring errors.
>
> I am planning to use the same architecture but with a couple of different details
you might consider.
>
> 1. I am going to eliminate the two shunts and run both alternator B leads through
one Hall Effect transducer. This eliminates the need to add switching for
the shunts. The AFS manual that I have (about 2 years old) shows provisions
for only one shunt.
>
> 2. I am going to use an LR3C regulator instead of the SB1B. With the install
kit, the SB1B is $308 more than the LR3C and the I don't see that the extra features
it has add any value in this application.
>
> You will have a main alt out annunciator light, plus voltage and current reading
on the AFS, plus you can probably program alarms for a low voltage condition
in the AFS, so the automatic turn on feature is not adding any value in my
opinion.
>
> You will also be able to read the voltage and standby alt current on the AFS,
so the blinking current warning light is also redundant.
>
> Great features for adding to an old TC aircraft, but you already have their functions
well covered.
>
> Just my 2 cents.
>
> Dick Kaehler
Appreciate the comments Dick.
#1 is a good idea. I actually meant to show a 2nd hall effect sensor on the aux
B-Lead vice a shunt. You're right that AFS does not have provision for two
shunts, but they do have provision for a shunt and a HE sensor. I have struggled
with how much instrumentation on current is enough or too much. I debated
having a single current sensor at the battery ground cable. AFS' software can
not presently deal with negative current flow signals (battery charging) so
this is why I ended up with this configuration. Never thought of having two alternator
B-Leads going thru one HE sensor. I like this. But if you have two
LR3 regulators, doesn't that mean they will both be online simultaneously (load
sharing)? Or are you dialing the voltage setting down on one of them so that
it only comes alive in case of failure of the primary? Or, are you keeping
the aux alternator field switch normally open, and only switching the aux alt
on in case of primary alt failure?
One thing I should have mentioned is that standard operating procedure is to have
both bus switches in the full on position during flight (both alternators available).
One thing I like about this is that no pilot action is required in
case of a primary alternator failure - the aux alternator just comes online and
no switching is immediately required. You might want to eventually turn off
the main bus / battery contactor depending on loads.
Anyway, some thought provoking comments so thank you.
--------
Highest Regards,
Noah Forden
RV-7A
Rhode Island
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Subject: | Re: Peer Review of Schematic |
user9253 wrote:
> Noah,
> Here are some suggestions for weight savings.
> 12AWG (or maybe 14) is big enough for the aux alternator and E-Bus.
> Have you done a load analysis on the E-Bus, adding the actual amperage of individual
loads (not individual fuse sizes)?
> The main power bus feed is not normally protected by a fuse. If you want to,
that is OK. But one ANL60 can protect both the alternator B lead and the main
power bus feed wire from excessive battery current. The alternator can not
put out much more than 60amps, so it is not necessary to use a fuse between the
alternator and main power bus.
> 6AWG is big enough for the main alternator unless you expect that the aircraft
load will continuously draw 60amps.
> Joe
Thanks for the input, Joe.
I am in process of sizing wires, fuses, and breakers so what is listed is preliminary.
I was under the impression that separate ANL fuses were used on both the B-lead
and the bus feed so that a short in either would not take down the other?
Although now that I think about it some more, if configured as you indicate, a
significant enough fault in either the primary B-lead or main bus feed would open
the single ANL fuse, which would take both the primary alternator and the
main bus offline. But the E-bus would not be affected, so maybe this is a good
trade off. Those ANL carriers ARE large and heavy. Why bother carrying the
weight?
I'm gonna have to sleep on this one.
Thanks again for your comments Joe.
--------
Highest Regards,
Noah Forden
RV-7A
Rhode Island
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Subject: | Re: Peer Review of Schematic |
>
> > What drove the decision to use an SD-20 in lieu
> > of the lighter and much less expensive SD-8?
> >
> > Bob . . .
>
>
>Bob, didn't we already hash these questions out?
Sorry. I have so many conversations going I have trouble
keeping track of them. Ignore all the above.
Bob . . .
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Subject: | Re: Peer Review of Schematic |
I should have posted some notes along with the schematic. Most have been covered.
One that has not involves the E-bus feed diode. I selected a Power Schottky
from Ixys. Cheapest outlet I found was Future Electronics:
http://ixdev.ixys.com/DataSheet/l227.pdf
The forward voltage drop for this diode is quite low, 0.29V at 20A, so the power
dissipated is also low, only
--------
Highest Regards,
Noah Forden
RV-7A
Rhode Island
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Subject: | Re: Peer Review of Schematic |
Noah,
You pointed out a good reason not to connect the main power bus to the same
fuse as the alternator. I do not think that any of the Z-drawings have a fuse
in the wire supplying power to the main bus. The theory is that a short circuit
in the wire will burn away the aluminum sheet metal and thus electrically
isolate the heavy copper wire once again. If you do a good job of wiring, and
I am sure you will, then the likelihood of a short circuit is remote, especially
if the wire is double insulated where it passes through the firewall or bulkheads.
The main purpose of the ANL fuse is to protect the battery and wires in case
the alternator shorts out (a rare occurrence). But if it does short out, one
would not want 400 amps draining the battery and heating wires.
> Second, to reduce current (and therefore overall voltage drop) across the diode(s).
That is true, but not by a significant amount. Diode redundancy and heat dissipation
are good reasons for using both diodes in the package, IMHO. Heat conducting
grease should be used between the diode and heatsink.
I do not see a problem with always having the E-bus alternate feed turned on.
You might consider having the aux-alternator on a separate switch so that you
can control it independently of the E-bus. If I remember correctly, Bob N.
said that connecting two alternators in parallel causes problems unless the voltage
regulator for the aux unit is set well below the set point of the main alternator.
Joe
--------
Joe Gores
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Subject: | Re: Peer Review of Schematic |
Noah,
If you use an LR3C instead of the SB1B, the normal operating condition would be
with the Aux alternator and alt battery feed off. You would be feeding the E-bus
through the diode under normal conditions.
With your scheme using the SB1B and the associated switch always on, I think your
E-bus would end up getting most of its power back through the relay, since
that will be the lower resistance path. I don't think the diode would be doing
much of anything unless the main contactor is on and the alt-feed relay is
off.
I think the auto-on feature of the SB1B would be a great thing on an aircraft with
a volt or ammeter stuck down on the bottom of the panel where you might not
notice the problem until it manifested itself after the battery had run down
and the gizmos started going on the fritz. I heard one such first hand dark
and stormy night story from my CFII. With all the low voltage signaling you
have, I would personally not be worried about missing the event or having to throw
the switch(s).
Dick
--------
rck
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