---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 01/06/14: 8 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:49 AM - Re: Illuminated Rocker switches - revisited (Carlos Trigo) 2. 12:58 AM - Re: Illuminated Rocker switches - revisited (Carlos Trigo) 3. 06:02 AM - Re: Proposed new Z diagram? (Robert L. Nuckolls, III) 4. 09:16 AM - Re: Proposed new Z diagram? (Dj Merrill) 5. 02:55 PM - Re: Illuminated Rocker switches - revisited (Bill Watson) 6. 05:17 PM - Re: Proposed new Z diagram? (user9253) 7. 06:23 PM - Re: Illuminated Rocker switches - revisited (Bob McCallum) 8. 07:01 PM - Re: Proposed new Z diagram? (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 12:49:17 AM PST US From: "Carlos Trigo" Subject: RE: AeroElectric-List: Illuminated Rocker switches - revisited Bob I am probably asking for too much, but my idea is: - To have the switch lamp as a "normal" illumination feature, which lits together with the Panel lights, and is dimmed by the Panel lights dimmer - To have the switch lamp as a warning feature, which lits whenever I turn On that particular circuit, and - be able to dim the lamp, in both ocasions. Independently of this being or not a good operation choice, how can this be achieved? What changes should I make in circuit B or C to achieve the features above? Thanks Carlos From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Bob McCallum Sent: domingo, 5 de Janeiro de 2014 16:48 Subject: RE: AeroElectric-List: Illuminated Rocker switches - revisited Not quite sure what it is you're trying to achieve. Circuit "A" gives night time illumination of the switch controlled by the dimmer but no indication if the switch is on or off. Circuit "B" gives full brightness indication of whether the switch is on or off but no night time illumination to identify the switch if it's off. Circuit "C" (with the addition of the diode) gives night time identification of the switch controlled by the dimmer and also full brightness indication of the on/off state day or night. (basically the functionality of both "A" & "B" combined) Are you asking for "C" to give night time illumination of the switch controlled by the dimmer, day time ONLY indication of the on/off state at full brightness and no indication of the on/off state at night???? This seems a bit odd as the illumination of the switch would indicate different things at different times depending upon the position of other switches. Could be confusing??? OR Are you asking that the "ON" condition of the switch is indicated by illumination of the lamp but also dimmed by the dimmer???? If this is the case then use circuit "B" but supply the lamp power from the dimmer circuit rather than B+ as you've shown. Bob McC _____ From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Carlos Trigo Sent: Sunday, January 05, 2014 9:54 AM Subject: RE: AeroElectric-List: Illuminated Rocker switches - revisited Thanks Bob McC So, in version "C", what changes should I make in the circuits, if I want the panel lights dimmer to dim the switch lamp whenever the switch is "On"? Carlos From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Bob McCallum Sent: domingo, 5 de Janeiro de 2014 14:13 Subject: RE: AeroElectric-List: Illuminated Rocker switches - revisited Simply place a diode in the lead from the dimmer to avoid back feeding the rest of the dimmed lamps. (This circuit "C" will illuminate the switch at full brightness whenever the switch is "on" regardless of dimmer position.) Bob McC _____ From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Carlos Trigo Sent: Sunday, January 05, 2014 7:00 AM Subject: AeroElectric-List: Illuminated Rocker switches - revisited Guys You remember my before-Christmas query about those Honeywell illuminated rocker switches. They are DPST switches, and with your help I came to the conclusion that the 2 upper vertical tabs are the 2 (independent) lamp contacts. So, I just have to use one pair of the lower horizontal tabs (one pole) to control the circuits I need, and the 2 upper vertical tabs to illuminate the lamp. Right! Now, the reason why I am now posting again about these switches is the way I am going to use them. Apologizing for the quality of the drawing, I designed the circuits in 3 versions: I have no doubt that version A and version B above are going to do what they are supposed to (explained below each version). My problem is version C, if I want the switch lamp to lit in both situations : - In night operation, the switch lamp will illuminate when I turn On the Panel Lights (through the Dimmer), and/or - Whenever I turn On the switch itself (for example, when I turn On the Landing Light in day operation, and want the switch lamp to be lit to warn me the LND Light is On when taxiing) I suppose that the version C above will give a nice short-circuit .. L So I need you electron experts to help me design the correct circuits for version C. Thanks Carlos ________________________________ Message 2 _____________________________________ Time: 12:58:29 AM PST US From: "Carlos Trigo" Subject: RE: AeroElectric-List: Illuminated Rocker switches - revisited Bill Thank you for all your comments, and information on your experience. It's always important to be aware of everyone's "hands on" experience, which helps in making decisions. For sure I will take it in consideration. Nevertheless, even being only a theoretical knowledge, I would like to know how could I achive my initial idea . Carlos "thru year 2 building the -10" Trigo -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Bill Watson Sent: domingo, 5 de Janeiro de 2014 19:42 Subject: Re: AeroElectric-List: Illuminated Rocker switches - revisited --> < Mauledriver@nc.rr.com> Carlos, based on my experience with these switches (350+ hours, <10% @night), I'd suggest taking a different approach to using the lights. I know you aren't necessarily looking for a different approach so I'll first mention 2 problems with using the lights to indicated on/off functionality: 1) The lights at full brightness are blinding at night. I'd suggest that they must be (adjustably) dimmed in all modes unless they are intended to signify a fault of some sort. I think that's what you are trying to accomplish in Version C. In that case, I'm not sure how you would accomplish full bright during daytime versus on and dimmed at night. Additionally, the dimmer would need to be setup so that at it's lowest setting, it would still be visible during day and night (difficult). 2) The switch lights are subject to a high frequency of failure. If the application was for gear retract and 'light-on' meant 'all green', I'm sure one would want to use a Honeywell series with an integrated lamp wired to indicate on/off status. What's the problem with this series? Well, once you've switched to LEDs, you've eliminated incandescent bulb failures and that's good. None of my LED bulbs have failed. But the bulbs do not seat reliably in these switches, at least not reliably enough on our vibrating panels . If used for landing gear status - you'd end up aborting the occasional landing for lamp socket unseats. They may be okay for indicating a landing light is on but my experience is that they will occasionally unseat. In my case, I use some un-switched indicators with the same lamp socket. For my low oil fault indicator, I glued the lamp in place to prevent unseats and avoid missing a fault indication. That said, I'm very happy with my panel switches but I took a slightly different approach that aligns well with the switches' characteristics. On my panel, the occasional bulb unseat is just a nuisance that is easily detected and corrected. The lighting on these switches are just 'back lighting' on my panel. At night, their backlighting completely eliminates the need for post lights or map lights to find, monitor and operate switches. At high intensity, they look great in full daylight though they are not really needed. Dimmed at night they are simply GREAT! The key point is that the labeling on the switches makes each switch's function and status clearly visible, day or night. When 'off', the word 'off' appears at the top of the switch. When 'on', only the function label is visible on the switch. There's no real need to have a light come on or off to indicate status. The status is visible and 'touchable'. The backlighting combined with the switch design and switch labeling make it east to find, monitor and operate each switch. And when a bulb unseats, I can easily see that one of my switches is unlit and needs to be tweaked. But otherwise, the (mal)functioning of the back light is meaningless. So, to anyone using this good looking series of Honeywell rockers, I suggest the following: - Using the lamps only for backlighting the switch top. It must be dimmable. Use LEDs with integral resistors. - Get custom labeling for each switch top. For simple on/off function, put 'off' at the top of each switch. - Consider using the good looking AML41 series of indicators for indicator lamps. They visually match the AML34 switch series, use the same lamps, etc. The indicator tops are available in colors (green, yellow, red). A two bulb model can be used for stuff like "Door L/R" open indications. For 'Door' and 'Oil Pressure', I used red tops, left the indicators undimmed and glued the LED bulbs in place. For 'Master Warn', 'Low Voltage', and 'Boost Pump', I used yellow and green indicator tops and made them dimmable since they may come on and stay on at night. Sources for these switches, indicators, LED bulbs, and labeling have all been listed on this forum. I had to do some additional searching for the switch models I needed for AP Nav Source switching and Flaps. Having the Flap switch physically resemble all my other switches looks good, but some will prefer a different type of switch. Works well for me though. Carlos, I know you weren't necessarily looking for that much input but hope it's useful. Bill "N215TG is halfway thru year 3" Watson www.buildersbooks.com www.homebuilthelp.com http://www.matronics.com/contribution http://www.matronics.com/Navigator?AeroElectric-List ________________________________ Message 3 _____________________________________ Time: 06:02:55 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Proposed new Z diagram? > An interesting and unexpected side effect - I've received > emails direct from others that say they are also interested in this > type of architecture, specifically the automatic "redundant" bus > feature for critical devices to get power from either the primary > or secondary power buses. Not sure what the term "automatic redundant" feature is all about . . . for what kind of failure is there value in offering an 'automatic' response? Let's try another tack . . . You said you wanted dual batteries and no always hot busses. Okay. Consider this variant on the Z07 work-in-process . . . http://tinyurl.com/mevf3n8 What failures in this architecture pose any unacceptable/unmanageable risks? In what way are your design goals yet to be realized? Bob . . . ________________________________ Message 4 _____________________________________ Time: 09:16:06 AM PST US Subject: Re: AeroElectric-List: Proposed new Z diagram? From: Dj Merrill Hi Bob McC, Thank you for looking things over and offering feedback. You make a very good point, and I'll have to think about this for a bit. The original intent was to have a system that could run specific critical equipment from either of two completely redundant power buses and battery power sources, and that both batteries would be charging when the alternator is enabled. Recently on the list we've been talking about running in an alternator-only mode, and I thought it a nice feature that my proposed architecture would allow this. However, I missed the fact that in doing so I now had no way to disable each of the separate buses if the alternator were running. Thank you for highlighting that! :-) Bob M offered a new dual battery Z-7 diagram this morning that offers more food for thought. I haven't had time to look at it with any detail, but I look forward to doing so later. If I am reading it correctly, at first glance it also seems to share a similar characteristic whereas both the main power bus and the endurance bus are always powered if the alternator is powered, with no way to individually remove power from each bus separately. A difference is that there is a single switch that controls the alternator and main battery contactor, and is wired such that the alternator will always be turned off first before the main battery contactor is turned off (ie, no alternator-only mode). With either the aux or main contactors on, both power buses will be enabled and there is no independent control to turn each bus off individually. Dual-Bat Z-7 requires two switches to shut down all power, and mine requires three, as you indicate. I could replace the alternator and main switches with a combined switch similar to Z-7, removing the alternator-only mode, which may be a good thing to do and simplifies the user experience, as well as allowing for each power bus to be separated and powered independently. I think the chances of both batteries failing and requiring an alternator-only mode are so remote that it is not worth worrying about. Thank you! -Dj On 01/05/2014 10:06 PM, Bob McCallum wrote: > > First; it would appear that what you have drawn will function. > > Is that function what you intend?? Or expect?? I'm not sure. It will power > the components you mention from either of two sources redundantly, but is it > what you want?? My second point below may be the gotcha you're alluding to > and may not have considered but I don't know. > > Second; turning off either the primary or secondary power (master?) switch, > as the circuit is drawn, will not turn off the respective primary or > secondary buss so long as the alternator is functioning. The alternator will > support the buss directly without benefit of the corresponding battery. The > master switches only serve to disconnect the batteries not turn off the > buss. If this is your desired goal then it will work. > This is not necessarily any sort of functional problem, just that you may > turn off one of these two master switches expecting the corresponding buss > to shut down and it won't. As long as you know that this is "normal" for the > way you've wired the circuit and are expecting this result then all is well. > Is there any conceivable instance when you would wish to shut down a buss > utilizing the corresponding master switch?? I so, then you need to be aware > that for this to happen you must also shut down the alternator. > > The down side is that in the case (heaven forbid) of a "crash" or "accident" > turning off the master switches does not "kill all power" as the electrical > system is still kept alive by the alternator if it is functioning and the > engine is turning. (even wind milling). Your wiring requires the > manipulation of three switches to fully shut down electrical power. > > Bob McC -- Dj Merrill - N1JOV - VP EAA Chapter 87 Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/ Glastar Flyer N866RH - http://deej.net/glastar/ ________________________________ Message 5 _____________________________________ Time: 02:55:51 PM PST US From: Bill Watson Subject: Re: AeroElectric-List: Illuminated Rocker switches - revisited Theoretically, I think the only way to get the logic you describe is with 2 lamps. That is, use the AML24G series instead of the AML24F that I assume you are looking at now. The 'G' has two lamps. Additionally you would need to two separate dimmers, one for each lamp circuit. I in fact have 3 dimmers on my panel - one for switches, one for indicators and one for the map light. You would in effect have the same configuration of dimmers. Interestingly enough, Perihelion Design sells the dimmers individually or as a discounted pack of 3 as I recall. Bill On 1/6/2014 3:57 AM, Carlos Trigo wrote: > > Bill > > Thank you for all your comments, and information on your experience. > > It's always important to be aware of everyone's "hands on" experience, > which helps in making decisions. For sure I will take it in consideration. > > Nevertheless, even being only a theoretical knowledge, I would like to > know how could I achive my initial idea ... > > Carlos "thru year 2 building the -10" Trigo > > -----Original Message----- > From: owner-aeroelectric-list-server@matronics.com > [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of > Bill Watson > Sent: domingo, 5 de Janeiro de 2014 19:42 > To: aeroelectric-list@matronics.com > Subject: Re: AeroElectric-List: Illuminated Rocker switches - revisited > > > --> > > > Carlos, based on my experience with these switches (350+ hours, <10% > @night), I'd suggest taking a different approach to using the lights. > > I know you aren't necessarily looking for a different approach so I'll > first mention 2 problems with using the lights to indicated on/off > > functionality: > > 1) The lights at full brightness are blinding at night. I'd suggest > that they must be (adjustably) dimmed in all modes unless they are > intended to signify a fault of some sort. I think that's what you are > trying to accomplish in Version C. In that case, I'm not sure how you > would accomplish full bright during daytime versus on and dimmed at > night. Additionally, the dimmer would need to be setup so that at > it's lowest setting, it would still be visible during day and night > (difficult). > > 2) The switch lights are subject to a high frequency of failure. If > the application was for gear retract and 'light-on' meant 'all green', > I'm sure one would want to use a Honeywell series with an integrated > lamp wired to indicate on/off status. What's the problem with this > series? > > Well, once you've switched to LEDs, you've eliminated incandescent > bulb failures and that's good. None of my LED bulbs have failed. But > the bulbs do not seat reliably in these switches, at least not > reliably enough on our vibrating panels . If used for landing gear > status - you'd end up aborting the occasional landing for lamp socket > unseats. > > They may be okay for indicating a landing light is on but my > experience is that they will occasionally unseat. In my case, I use > some un-switched indicators with the same lamp socket. For my low oil > fault indicator, I glued the lamp in place to prevent unseats and > avoid missing a fault indication. > > That said, I'm very happy with my panel switches but I took a slightly > different approach that aligns well with the switches' characteristics. > > On my panel, the occasional bulb unseat is just a nuisance that is > easily detected and corrected. > > The lighting on these switches are just 'back lighting' on my panel. > At night, their backlighting completely eliminates the need for post > lights or map lights to find, monitor and operate switches. At high > intensity, they look great in full daylight though they are not really > needed. > > Dimmed at night they are simply GREAT! > > The key point is that the labeling on the switches makes each switch's > function and status clearly visible, day or night. When 'off', the > word 'off' appears at the top of the switch. When 'on', only the > function label is visible on the switch. There's no real need to have > a light come on or off to indicate status. The status is visible and > 'touchable'. The backlighting combined with the switch design and > switch labeling make it east to find, monitor and operate each switch. > > And when a bulb unseats, I can easily see that one of my switches is > unlit and needs to be tweaked. But otherwise, the (mal)functioning of > the back light is meaningless. > > So, to anyone using this good looking series of Honeywell rockers, I > suggest the following: > > - Using the lamps only for backlighting the switch top. It must be > dimmable. Use LEDs with integral resistors. > > - Get custom labeling for each switch top. For simple on/off > function, put 'off' at the top of each switch. > > - Consider using the good looking AML41 series of indicators for > indicator lamps. They visually match the AML34 switch series, use the > same lamps, etc. The indicator tops are available in colors (green, > yellow, red). A two bulb model can be used for stuff like "Door L/R" > > open indications. For 'Door' and 'Oil Pressure', I used red tops, > left the indicators undimmed and glued the LED bulbs in place. For > 'Master Warn', 'Low Voltage', and 'Boost Pump', I used yellow and > green indicator tops and made them dimmable since they may come on and > stay on at night. > > Sources for these switches, indicators, LED bulbs, and labeling have > all been listed on this forum. I had to do some additional searching > for the switch models I needed for AP Nav Source switching and Flaps. > > Having the Flap switch physically resemble all my other switches looks > good, but some will prefer a different type of switch. Works well for > me though. > > Carlos, I know you weren't necessarily looking for that much input but > hope it's useful. > > Bill "N215TG is halfway thru year 3" Watson > > www.aeroelectric.com > > www.buildersbooks.com > > www.homebuilthelp.comwww.mypilotstore.com > > www.mrrace.comhref="http://www.matronics.com/contribution">http://www.matronics.com/contribution > > http://www.matronics.com/Navigator?AeroElectric-List > > http://forums.matronics.com > > * > > * > > No virus found in this message. > Checked by AVG - www.avg.com > ________________________________ Message 6 _____________________________________ Time: 05:17:21 PM PST US Subject: AeroElectric-List: Re: Proposed new Z diagram? From: "user9253" Attached is one more recipe to help fill the 1000 page cookbook of electrical architectures. :-) To keep it simple, this schematic has only one bus which is fed from both ends. The failure of any one wire or terminal or switch or relay will not interrupt power to the bus. In the event of low voltage, the pilot should shut off master switch #1. Doing so will shut off power to the alternator field and master contactor coil, thus conserving battery energy. It is up to the pilot to shut off any other unnecessary loads. Although this architecture is intended for a simple aircraft, the single bus could supply power to an IFR instrument panel or to an electrically dependent engine without danger of power loss due to the failure of any one component. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=416653#416653 Attachments: http://forums.matronics.com//files/simple_elect_system_102.pdf ________________________________ Message 7 _____________________________________ Time: 06:23:07 PM PST US From: Bob McCallum Subject: RE: AeroElectric-List: Illuminated Rocker switches - revisited Carlos; The simplest way to achieve what you're asking would be to use version "C" with the diode in the lead coming from the panel light dimmer then add another dimmer between your B+ supply at the bottom of the switch and the switch also through a diode to prevent back feed between the two dimmers. This way your panel light dimmer will control the intensity of the identification illumination and the dimmer in the B+ supply will control the intensity of the "on" indication. These two uses of the lamp will however lead to uncertainty as to what the lamp indicates because there will no way to differentiate between background illumination and "on" indication. Depending on the relative dimmer settings the brightness might change between the two functions but either function could override the other in terms of brightness. This will function as you've asked, but not too useful in my humble opinion because of the uncertainty in what is being indicated. Bob McC _____ From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Carlos Trigo Sent: Monday, January 06, 2014 3:48 AM Subject: RE: AeroElectric-List: Illuminated Rocker switches - revisited Bob I am probably asking for too much, but my idea is: - To have the switch lamp as a "normal" illumination feature, which lits together with the Panel lights, and is dimmed by the Panel lights dimmer - To have the switch lamp as a warning feature, which lits whenever I turn On that particular circuit, and - be able to dim the lamp, in both ocasions. Independently of this being or not a good operation choice, how can this be achieved? What changes should I make in circuit B or C to achieve the features above? Thanks Carlos From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Bob McCallum Sent: domingo, 5 de Janeiro de 2014 16:48 Subject: RE: AeroElectric-List: Illuminated Rocker switches - revisited Not quite sure what it is you're trying to achieve. Circuit "A" gives night time illumination of the switch controlled by the dimmer but no indication if the switch is on or off. Circuit "B" gives full brightness indication of whether the switch is on or off but no night time illumination to identify the switch if it's off. Circuit "C" (with the addition of the diode) gives night time identification of the switch controlled by the dimmer and also full brightness indication of the on/off state day or night. (basically the functionality of both "A" & "B" combined) Are you asking for "C" to give night time illumination of the switch controlled by the dimmer, day time ONLY indication of the on/off state at full brightness and no indication of the on/off state at night???? This seems a bit odd as the illumination of the switch would indicate different things at different times depending upon the position of other switches. Could be confusing??? OR Are you asking that the "ON" condition of the switch is indicated by illumination of the lamp but also dimmed by the dimmer???? If this is the case then use circuit "B" but supply the lamp power from the dimmer circuit rather than B+ as you've shown. Bob McC _____ From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Carlos Trigo Sent: Sunday, January 05, 2014 9:54 AM Subject: RE: AeroElectric-List: Illuminated Rocker switches - revisited Thanks Bob McC So, in version "C", what changes should I make in the circuits, if I want the panel lights dimmer to dim the switch lamp whenever the switch is "On"? Carlos From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Bob McCallum Sent: domingo, 5 de Janeiro de 2014 14:13 Subject: RE: AeroElectric-List: Illuminated Rocker switches - revisited Simply place a diode in the lead from the dimmer to avoid back feeding the rest of the dimmed lamps. (This circuit "C" will illuminate the switch at full brightness whenever the switch is "on" regardless of dimmer position.) Bob McC _____ From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Carlos Trigo Sent: Sunday, January 05, 2014 7:00 AM Subject: AeroElectric-List: Illuminated Rocker switches - revisited Guys You remember my before-Christmas query about those Honeywell illuminated rocker switches. They are DPST switches, and with your help I came to the conclusion that the 2 upper vertical tabs are the 2 (independent) lamp contacts. So, I just have to use one pair of the lower horizontal tabs (one pole) to control the circuits I need, and the 2 upper vertical tabs to illuminate the lamp. Right! Now, the reason why I am now posting again about these switches is the way I am going to use them. Apologizing for the quality of the drawing, I designed the circuits in 3 versions: I have no doubt that version A and version B above are going to do what they are supposed to (explained below each version). My problem is version C, if I want the switch lamp to lit in both situations : - In night operation, the switch lamp will illuminate when I turn On the Panel Lights (through the Dimmer), and/or - Whenever I turn On the switch itself (for example, when I turn On the Landing Light in day operation, and want the switch lamp to be lit to warn me the LND Light is On when taxiing) I suppose that the version C above will give a nice short-circuit .. :-( So I need you electron experts to help me design the correct circuits for version C. Thanks Carlos ________________________________ Message 8 _____________________________________ Time: 07:01:58 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Proposed new Z diagram? > the alternator will always be turned off first >before the main battery contactor is turned off (ie, no alternator-only >mode). With either the aux or main contactors on, both power buses will >be enabled and there is no independent control to turn each bus off >individually. Assuming that the Viking engine with the as- proposed alternator does run gracefully in an alternator only mode, then the whole inter-linked switch philsosopy for battery and alternator is moot. This figure illustrates the opptions for being relieved of that constraint . . . http://tinyurl.com/mhblorq > Dual-Bat Z-7 requires two switches to shut down all power, and mine >requires three, as you indicate. I could replace the alternator and >main switches with a combined switch similar to Z-7, removing the >alternator-only mode, which may be a good thing to do and simplifies the >user experience, as well as allowing for each power bus to be separated >and powered independently. I think the chances of both batteries >failing and requiring an alternator-only mode are so remote that it is >not worth worrying about. How does a battery fail? If such a failure occurs in flight, how do you know it has happened? What light comes on to say, "Battery X Fail"? You have articulated some goals for addressing a constellation of failures as yet not clearly defined. When conducting an FMEA on a system or product the following questions are posed and answers sought: How might this part fail? How will I know that it failed? Can the effects of the failure be immediately known and dealt with in a simple, prescribed manner? Is the failure pre-flight detectable? If not can it be made detectable. I that's not possible/ practical . . . what sort of testing is called for and at what intervals? How does any particular failure impact probability of comfortable termination of a flight? (a) Will any identified failure produce an immediate risk to ship's systems? (b) Will any identified failure over-tax my abilities to manage the event while maintaining competent control of the airplane? I have split the DC POWER MASTER into two switches which increases the number of power management controls to a total of 6. That gives you 36 possible combinations of switch positions some small number of which will result in the engine stopping . . . so those are easy to eliminate. Of the remaining combinations, what are the criteria for selecting/rejecting any combination that keeps the engine running and at least some stuff lit on the panel? At some point, after all the colors are laid down with the favorite brush strokes, you need to craft the pilot's operating handbook for how the switches are used. Do all those options serve a predictable, useful purpose? It's one thing to have so many options and control over those options . . . consider that each option should be deduced and prescribed in advance. Lots of options can work against you should one become reduced to a game of "flipping switches until things work better" while distracting concentration from your duties as a pilot. 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