---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 10/06/03: 18 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:21 AM - Re: Re: Rrelay diagram for Microair PTT (Jeff Hottle) 2. 07:22 AM - Re: Re: Rrelay diagram for Microair PTT (Jeff Hottle) 3. 08:58 AM - Re: Re: Rrelay diagram for Microair PTT (Mark Phillips) 4. 10:04 AM - Re: Re: Rrelay diagram for Microair PTT (Jeff Hottle) 5. 10:48 AM - Re: Re: Relay diagram for Microair PTT (Robert L. Nuckolls, III) 6. 11:43 AM - Alternator Noise in Headset (Pete Waters) 7. 11:48 AM - Re: Re: Rrelay diagram for Microair PTT (Mark Phillips) 8. 03:39 PM - Re: Fuse Blocks, fuses, fusible links and CBs (Chris Good) 9. 04:44 PM - Switched gnd? (Larry Bowen) 10. 05:29 PM - Re: Switched gnd? (Robert L. Nuckolls, III) 11. 07:14 PM - Re: Switched gnd? (Robinson, Chad) 12. 09:01 PM - Re: Switched gnd? (Lyle Peterson) 13. 09:01 PM - Re: Re: Relay diagram for Microair PTT (Sigma Eta Aero) 14. 09:01 PM - Battery Contactor vibration problem (Vince Ackerman) 15. 09:04 PM - Re: Switched gnd? (Larry Bowen) 16. 09:11 PM - Re: Switched gnd? (Larry Bowen) 17. 09:56 PM - Re: Switched gnd? (Lyle Peterson) 18. 11:00 PM - Re: Switched gnd? (Robinson, Chad) ________________________________ Message 1 _____________________________________ Time: 07:21:35 AM PST US From: "Jeff Hottle" Subject: Re: AeroElectric-List: Re: Rrelay diagram for Microair PTT --> AeroElectric-List message posted by: "Jeff Hottle" Don't lose your hair, Mark :) Bob's drawing is good EXCEPT you need to run the red wires to the opposite relays. >--> AeroElectric-List message posted by: Mark Phillips > >Ooops- sorry, my screw-up----I meant the Pilot Mic Hi & Co-pilot Mic Hi, not Mic Lo- from the >drawing it appears that when the mic is keyed , which if I understand this, the coil in the >relay is grounded, switching the contacts from the position shown, and the respective circuit >from the radio to the mic will OPEN or am I that electrically challenged? 8-) > >Not meaning to pester, but I'm getting a bald spot from all the head-scratchin'! >Mark do not archive > >> on the Mic relay circuit cited below, should not the Mic Hi & Mic >> >Lo connections to the radio be made to the NO contacts of the relays? >> >> don't know why. you described the operation you wanted and I believe >> the circuit I drew will do that. I didn't take time to noodle out >> Microair's circuit . . . it probably does work as they intended >> but I didn't have time to wade through their schematic and erratic >> font displays. >> Bob . . . ________________________________ Message 2 _____________________________________ Time: 07:22:55 AM PST US From: "Jeff Hottle" Subject: Re: AeroElectric-List: Re: Rrelay diagram for Microair PTT --> AeroElectric-List message posted by: "Jeff Hottle" Oops, that should be the BLUE wires. I didn't have my morning coffee yet. ________________________________ Message 3 _____________________________________ Time: 08:58:46 AM PST US From: Mark Phillips Subject: Re: AeroElectric-List: Re: Rrelay diagram for Microair PTT --> AeroElectric-List message posted by: Mark Phillips Interesting- that would also work, sharing the three functions between the two relays (mic signal on one, PTT operate and opposite mic disable on the other). Can you confirm that relocating the red and blue wires from the radio from the NC contact to the adjacent NO contact would also work, using one relay for each separate mic? Mark - do not archive Jeff Hottle wrote: > --> AeroElectric-List message posted by: "Jeff Hottle" > > Oops, that should be the BLUE wires. I didn't have my morning coffee yet. > ________________________________ Message 4 _____________________________________ Time: 10:04:14 AM PST US From: "Jeff Hottle" Subject: Re: AeroElectric-List: Re: Rrelay diagram for Microair PTT --> AeroElectric-List message posted by: "Jeff Hottle" I believe the idea behind Bob's schematic is to disconnect the opposite mic when one of the PTT buttons is pressed. If you want to use the built-in intercom you need the mic signals when you're not transmitting, so they need to be on the NC side. A while back I drew a similar schematic using double-pole relays and a 3-position toggle for pilot only, pilot priority, or first-come first-served. Jeff Mark Phillips wrote: >Interesting- that would also work, sharing the three functions between the two >relays (mic signal on one, PTT operate and opposite mic disable on the other). >Can you confirm that relocating the red and blue wires from the radio from the >NC contact to the adjacent NO contact would also work, using one relay for each >separate mic? > >Mark - do not archive ________________________________ Message 5 _____________________________________ Time: 10:48:14 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Relay diagram for Microair PTT --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 03:47 PM 10/5/2003 -0500, you wrote: >--> AeroElectric-List message posted by: Mark Phillips > >Ooops- sorry, my screw-up----I meant the Pilot Mic Hi & Co-pilot Mic Hi, >not Mic Lo- from the >drawing it appears that when the mic is keyed , which if I understand >this, the coil in the >relay is grounded, switching the contacts from the position shown, and the >respective circuit >from the radio to the mic will OPEN or am I that electrically challenged? 8-) > >Not meaning to pester, but I'm getting a bald spot from all the >head-scratchin'! >Mark do not archive Some folks spotted an error I introduced while "prettying up" the drawing . . . got the relay pull-down leads reversed to their respective microphone jacks. Thank's for the sharp eyes guys! The corrected last page for instructions can be accessed at: http://www.aeroelectric.com/Catalog/avionics/fcfs_ptt.pdf The whole instruction manual with corrections incorporated is available at: http://www.aeroelectric.com/Catalog/avionics/760imB.pdf Bob . . . ________________________________ Message 6 _____________________________________ Time: 11:43:21 AM PST US From: Pete Waters Subject: AeroElectric-List: Alternator Noise in Headset --> AeroElectric-List message posted by: Pete Waters --0-1011535678-1065465776=:8230 Bob, I'm starting to develop an electrical problem in my RV-4 and I'm hoping you can help me diagnose it. I bought the RV-4 (completed) last year. It was built in 1988 and I'm the fourth owner. It's a solid airplane, but the documentation is thin and from the logbooks it appears that the electrical stuff (lights, radios) were added piecemeal over the plnae's first few years, so the electrical system is a bit tangled. For example, my nav light circuit breaker kept popping. I finally figured out that the builder / modifier has three 2-amp bulbs (6 amps) going through a 5-amp CB. So I replaced the 5A CB with a 10A CB. Worked great. However, on my next flight, I started hearing a whine in my headset. More of a tone, actually, sounding a lot like Morse from an VOR. Originally intermittent, and as I returned from a cross country it became almost constant. The whine / tone is present with the radios off, strobes off, and alternator off, although I didn't think to pull the breakers on those circuits. I can hear it in the background during intercom and radio reception. It disappears briefly after a radio transmission and then returns after a few seconds. The plane has a voltmeter, no ammeter, and I immediately noticed that the voltage was increasing to about 15.5 V and fluctuating there for a while. Then it settled down to 14.5 V. The problem comes and goes and is not entirely repeatable. Also, perhaps related and perhaps not, the LORAN stopped working a few weeks back. I had thought it had just died due to age, and I was buying a GPS anyway, so I've just left it off since and plan to remove it. I'm thinking the obvious thought that the alternator's going. Because the plane has so little documentation, I don't know the specifics of the alternator at all or how old it is, just that it's been working so far. My A&P found nothing wrong with it at the last annual 60 hours ago. I'm wondering if the impending alternator failure is putting out RF that's getting into the headset and was jamming the LORAN. Also, I've noticed that with the electrical system fully loaded up, the voltmeter needle also starts rapidly fluctuating at 14.5-15.5V. I see this when I turn on the landing light. Due to the lack of documentation I have no idea how many total amps are actually flowing through the system, so I'm wondering if turning on the landing lights actually puts the plane's total current draw above the rated output of the alternator. Is fluctuating system voltage a sign of that? If you could offer any thoughts on this, I'd appreciate it. Best, Pete Waters (registered for your class in Watsonville) --------------------------------- --0-1011535678-1065465776=:8230
Bob,
 
  I'm starting to develop an electrical problem in my RV-4 and I'm hoping you can help me diagnose it.
  I bought the RV-4 (completed) last year.  It was built in 1988 and I'm the fourth owner. It's a solid airplane, but the documentation is thin and from the logbooks it appears that the electrical stuff (lights, radios) were added piecemeal over the plnae's first few years, so the electrical system is a bit tangled.  For example, my nav light circuit breaker kept popping.  I finally figured out that the builder / modifier has three 2-amp bulbs (6 amps) going through a 5-amp CB.  So I replaced the 5A CB with a 10A CB.  Worked great. 
  However, on my next flight, I started hearing a whine in my headset.  More of a tone, actually, sounding a lot like Morse from an VOR.  Originally intermittent, and as I returned from a cross country it became almost constant.  The whine / tone is present with the radios off, strobes off, and alternator off, although I didn't think to pull the breakers on those circuits.  I can hear it in the background during intercom and radio reception. It disappears briefly after a radio transmission and then returns after a few seconds.  The plane has a voltmeter, no ammeter, and I immediately noticed that the voltage was increasing to about 15.5 V and fluctuating there for a while.  Then it settled down to 14.5 V.  The problem comes and goes and is not entirely repeatable.  Also, perhaps related and perhaps not, the LORAN stopped working a few weeks back.  I had thought it had just died due to age, and I was buying a GPS anyw ay, so I've just left it off since and plan to remove it.
  I'm thinking the obvious thought that the alternator's going.  Because the plane has so little documentation, I don't know the specifics of the alternator at all or how old it is, just that it's been working so far.  My A&P found nothing wrong with it at the last annual 60 hours ago.  I'm wondering if the impending alternator failure is putting out RF that's getting into the headset and was jamming the LORAN.
  Also, I've noticed that with the electrical system fully loaded up, the voltmeter needle also starts rapidly fluctuating at 14.5-15.5V.  I see this when I turn on the landing light.  Due to the lack of documentation I have no idea how many total amps are actually flowing through the system, so I'm wondering if turning on the landing lights actually puts the plane's total current draw above the rated output of the alternator.  Is fluctuating system voltage a sign of that?
  If you could offer any thoughts on this, I'd appreciate it.
 
Best,
Pete Waters
(registered for your class in Watsonville)

--0-1011535678-1065465776=:8230-- ________________________________ Message 7 _____________________________________ Time: 11:48:36 AM PST US From: Mark Phillips Subject: Re: AeroElectric-List: Re: Rrelay diagram for Microair PTT --> AeroElectric-List message posted by: Mark Phillips ah HA! Intercom function! Now I see it- thanks! Mark do not archive Jeff Hottle wrote: > --> AeroElectric-List message posted by: "Jeff Hottle" > > I believe the idea behind Bob's schematic is to disconnect the opposite > mic when one of the PTT buttons is pressed. > > If you want to use the built-in intercom you need the mic signals when > you're not transmitting, so they need to be on the NC side. > > A while back I drew a similar schematic using double-pole relays and a > 3-position toggle for pilot only, pilot priority, or first-come > first-served. > > Jeff > > Mark Phillips wrote: > > >Interesting- that would also work, sharing the three functions between the two > >relays (mic signal on one, PTT operate and opposite mic disable on the other). > >Can you confirm that relocating the red and blue wires from the radio from the > >NC contact to the adjacent NO contact would also work, using one relay for each > >separate mic? > > > >Mark - do not archive > ________________________________ Message 8 _____________________________________ Time: 03:39:26 PM PST US From: "Chris Good" Subject: Re: AeroElectric-List: Fuse Blocks, fuses, fusible links and CBs --> AeroElectric-List message posted by: "Chris Good" Greg, As far as the flap motor goes, I've got a note that it takes 5 amps, although I don't remember where I found that. In any case, I used 16 awg wire & a 10 amp fuse. It's operated perfectly for 600 hrs with no nuisance fuse trips. Regards, Chris Good, http://rv.supermatrix.com West Bend, WI RV-6A 86CG, flying 600 hrs BTW, I'm expecting to be in Honolulu for Thanksgiving. Maybe I'll get a chance to see your project. -- --------- Original Message --------- DATE: Fri, 3 Oct 2003 18:24:59 From: Greg Grigson >--> AeroElectric-List message posted by: Greg Grigson > >--0-361577249-1065230699=:58092 > >Bob, > I am using a derivative of Figure Z-11 architecture for an RV6. I want to feed the electronic ignition from a hot battery bus. The LSE installation instructions say to use a "pullable" 5 amp breaker. The Aeroelectric connection mentions use of a fusible link in this application. I would much prefer a fusible link with an on/off switch over a CB. Do these electronic ignition systems nuisance trip in general? I thought they were supposed to be incredibly reliable (That's why I bought it!!). > > What would you suggest for a feed to the flap motor. I thought I read something about this is one particular animal that can nuisance trip. If you were to recommend a CB application how would you power that off say the main bus/fuse block? I would prefer to keep the ALT FLD CB the only breaker on the panel, if practical. > > I haven't seen listed the expected current draw for the flap motor. Can anybody help me out here? > >Thanks. >Greg Grigson >Honolulu > > ________________________________ Message 9 _____________________________________ Time: 04:44:06 PM PST US From: "Larry Bowen" Subject: AeroElectric-List: Switched gnd? --> AeroElectric-List message posted by: "Larry Bowen" The rule of thumb seems to be to switch the positive line rather than the negative/ground for a typical circut. I have the need to break this rule and wire my fuel pump positve with no switch and switch the ground to turn it on/off. Is this a huge no-no? Bad style? No big deal? Why does it matter? Thanks, - Larry Bowen Larry@BowenAero.com http://BowenAero.com ________________________________ Message 10 ____________________________________ Time: 05:29:27 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Switched gnd? --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 07:45 PM 10/6/2003 -0400, you wrote: >--> AeroElectric-List message posted by: "Larry Bowen" > >The rule of thumb seems to be to switch the positive line rather than >the negative/ground for a typical circut. I have the need to break this >rule and wire my fuel pump positve with no switch and switch the ground >to turn it on/off. Is this a huge no-no? Bad style? No big deal? Why >does it matter? > >Thanks, It doesn't. Control circuitry aboard aircraft are done both ways. I'm unaware of any such rule-of-thumb . . . Bob . . . -------------------------------------------- ( Knowing about a thing is different than ) ( understanding it. One can know a lot ) ( and still understand nothing. ) ( C.F. Kettering ) -------------------------------------------- ________________________________ Message 11 ____________________________________ Time: 07:14:42 PM PST US Subject: RE: AeroElectric-List: Switched gnd? From: "Robinson, Chad" --> AeroElectric-List message posted by: "Robinson, Chad" > The rule of thumb seems to be to switch the positive line rather than > the negative/ground for a typical circut. I have the need to break this > rule and wire my fuel pump positve with no switch and switch the ground > to turn it on/off. Is this a huge no-no? Bad style? No big deal? Why > does it matter? This sounds like more of an issue in high voltage AC electrical wiring such as you have in your home. There you want to switch the "hot" side so that when the switch is off, there is mains voltage reaching the device/circuit. Otherwise, if the device (say, a lamp) was on, the white (neutral/return) wire would be hot, which can create a dangerous situation for anybody mucking with the wires. It's a safety issue, with lots of ramifications for both electricians and product designers. But for a 12V circuit? My car has several circuits wired this way. I can't see why it would be a problem in a plane. Maybe Bob has some guidance here? Regards, Chad ________________________________ Message 12 ____________________________________ Time: 09:01:06 PM PST US From: "Lyle Peterson" Subject: RE: AeroElectric-List: Switched gnd? --> AeroElectric-List message posted by: "Lyle Peterson" I for one would want to switch the positive side of the circuit. If the device being controlled by the switch failed in a shorted mode, there would still be positive voltage to it. The switch would not save the device as it is grounded to the frame of the vehicle, airplane. In a composite airframe this may not be a concern. In a metal airplane I would definitely not switch the negative side of the circuit. My milli pennies worth. Gee, opinions are depreciating rather rapidly, aren't they? Lyle -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robinson, Chad Subject: RE: AeroElectric-List: Switched gnd? --> AeroElectric-List message posted by: "Robinson, Chad" --> > The rule of thumb seems to be to switch the positive line rather than > the negative/ground for a typical circut. I have the need to break > this rule and wire my fuel pump positve with no switch and switch the > ground to turn it on/off. Is this a huge no-no? Bad style? No big > deal? Why does it matter? This sounds like more of an issue in high voltage AC electrical wiring such as you have in your home. There you want to switch the "hot" side so that when the switch is off, there is mains voltage reaching the device/circuit. Otherwise, if the device (say, a lamp) was on, the white (neutral/return) wire would be hot, which can create a dangerous situation for anybody mucking with the wires. It's a safety issue, with lots of ramifications for both electricians and product designers. But for a 12V circuit? My car has several circuits wired this way. I can't see why it would be a problem in a plane. Maybe Bob has some guidance here? Regards, Chad == direct advertising on the Matronics Forums. == http://www.matronics.com/trouble-report == == ________________________________ Message 13 ____________________________________ Time: 09:01:06 PM PST US From: Sigma Eta Aero Subject: Re: AeroElectric-List: Re: Relay diagram for Microair PTT --> AeroElectric-List message posted by: Sigma Eta Aero --0-1904218001-1065499228=:60162 Good stuff, thanks Bob. Now if you'll hold my hand just a minute longer and suggest the "perfect" DigiKey diodes to go with both the OV disconnect relay and these relays I would be grateful. The pic on your site shows a 1N4005 but there are about a dozen of these that show up in the DigiKey website. Also, where are the red and white connectors that come with the B&C OV module kit best used? Joa --------------------------------- --0-1904218001-1065499228=:60162
Good stuff, thanks Bob.  Now if you'll hold my hand just a minute longer and suggest the "perfect" DigiKey diodes to go with both the OV disconnect relay and these relays I would be grateful.  The pic on your site shows a 1N4005 but there are about a dozen of these that show up in the DigiKey website. 
 
Also, where are the red and white connectors that come with the B&C OV module kit best used?
 
Joa

--0-1904218001-1065499228=:60162-- ________________________________ Message 14 ____________________________________ Time: 09:01:37 PM PST US Subject: AeroElectric-List: Battery Contactor vibration problem From: Vince Ackerman --> AeroElectric-List message posted by: Vince Ackerman I installed a battery master switch with contactor (one or the 3 terminal ones sold by Aircraft Spruce) on my Rotorway 162f project. For reasons of space I installed it upside down. While testing out the electrical system I noticed that tapping with a small rubber mallet on the bracket that it's mounted to will cause it to interrupt the power momentarily. It doesn't matter if I tap from top or bottom, it seems to disconnect for a split second. I know it's disconnecting because my rotor tach goes through it's initialization test on first power up, and it's doing that every time. Also, other indicator lights flicker, so it's not just the tach, nor loose battery leads, etc. You can understand my hesitation about using this since it's a helo (they aren't the smoothest) with two FADEC's that can't be electrically interrupted. Are there any stronger or more reliable contactors, perhaps even solid state? Any suggestions for how to fix this? Thanks Vince Ackerman N777FB ________________________________ Message 15 ____________________________________ Time: 09:04:06 PM PST US From: "Larry Bowen" Subject: RE: AeroElectric-List: Switched gnd? --> AeroElectric-List message posted by: "Larry Bowen" That's good news. I guess I just developed that impression during my miniscule electrical experience. I know some light-weight circuits switch the ground, i.e. for enunciator lights, etc -- but I thought bigger 'appliances' had to have the + switched. Glad to hear that's not always the case. Thanks. - Larry Bowen Larry@BowenAero.com http://BowenAero.com > -----Original Message----- > From: Robert L. Nuckolls, III [mailto:bob.nuckolls@cox.net] > Sent: Monday, October 06, 2003 8:29 PM > To: aeroelectric-list@matronics.com > Subject: Re: AeroElectric-List: Switched gnd? > > > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > --> > > At 07:45 PM 10/6/2003 -0400, you wrote: > >--> AeroElectric-List message posted by: "Larry Bowen" > >--> > > > >The rule of thumb seems to be to switch the positive line > rather than > >the negative/ground for a typical circut. I have the need to break > >this rule and wire my fuel pump positve with no switch and > switch the > >ground to turn it on/off. Is this a huge no-no? Bad style? No big > >deal? Why does it matter? > > > >Thanks, > > It doesn't. Control circuitry aboard aircraft are done > both ways. I'm unaware of any such rule-of-thumb . . . > > Bob . . . > > -------------------------------------------- > ( Knowing about a thing is different than ) > ( understanding it. One can know a lot ) > ( and still understand nothing. ) > ( C.F. Kettering ) > -------------------------------------------- ________________________________ Message 16 ____________________________________ Time: 09:11:31 PM PST US From: "Larry Bowen" Subject: RE: AeroElectric-List: Switched gnd? --> AeroElectric-List message posted by: "Larry Bowen" The fuse/breaker would provide protection. Would it not? - Larry Bowen Larry@BowenAero.com http://BowenAero.com > -----Original Message----- > From: Lyle Peterson [mailto:lyleap@access4less.net] > Sent: Tuesday, October 07, 2003 12:01 AM > To: aeroelectric-list@matronics.com > Subject: RE: AeroElectric-List: Switched gnd? > > > --> AeroElectric-List message posted by: "Lyle Peterson" > --> > > I for one would want to switch the positive side of the > circuit. If the device being controlled by the switch failed > in a shorted mode, there would still be positive voltage to > it. The switch would not save the device as it is grounded > to the frame of the vehicle, airplane. In a composite > airframe this may not be a concern. In a metal airplane I > would definitely not switch the negative side of the circuit. > > My milli pennies worth. > > Gee, opinions are depreciating rather rapidly, aren't they? > > Lyle > > -----Original Message----- > From: owner-aeroelectric-list-server@matronics.com > [mailto:owner-aeroelectric-list-server@matronics.com] On > Behalf Of Robinson, Chad > To: aeroelectric-list@matronics.com > Subject: RE: AeroElectric-List: Switched gnd? > > > --> AeroElectric-List message posted by: "Robinson, Chad" > --> > > > The rule of thumb seems to be to switch the positive line > rather than > > the negative/ground for a typical circut. I have the need to break > > this rule and wire my fuel pump positve with no switch and > switch the > > ground to turn it on/off. Is this a huge no-no? Bad > style? No big > > deal? Why does it matter? > > This sounds like more of an issue in high voltage AC > electrical wiring such as you have in your home. There you > want to switch the "hot" side so that when the switch is off, > there is mains voltage reaching the device/circuit. > Otherwise, if the device (say, a lamp) was on, the white > (neutral/return) wire would be hot, which can create a > dangerous situation for anybody mucking with the wires. It's > a safety issue, with lots of ramifications for both > electricians and product designers. > > But for a 12V circuit? My car has several circuits wired this > way. I can't see why it would be a problem in a plane. Maybe > Bob has some guidance here? > > Regards, > Chad > > > == > direct advertising on the Matronics Forums. > == > http://www.matronics.com/trouble-report > == > == > > > ============ > Matronics Forums. > ============ > http://www.matronics.com/trouble-report > > ============ > http://www.matronics.com/FAQ/AeroElectric-List.htm > Search Engine: http://www.matronics.com/search > ============ > > > > > > ________________________________ Message 17 ____________________________________ Time: 09:56:56 PM PST US From: "Lyle Peterson" Subject: RE: AeroElectric-List: Switched gnd? --> AeroElectric-List message posted by: "Lyle Peterson" Depends on which side is fused or breakered (is that a word?) If the postive side is fused it would protect it. If the problem is one of wiring the switch only to the negative side for some reason, I am guessing that the same reasons apply to the fuse or breaker. That means the fuse would be in the negative side and little or no protection. Another 2 mils worth of opinion. Lyle -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Larry Bowen Subject: RE: AeroElectric-List: Switched gnd? --> AeroElectric-List message posted by: "Larry Bowen" --> The fuse/breaker would provide protection. Would it not? - Larry Bowen Larry@BowenAero.com http://BowenAero.com ________________________________ Message 18 ____________________________________ Time: 11:00:22 PM PST US Subject: RE: AeroElectric-List: Switched gnd? From: "Robinson, Chad" --> AeroElectric-List message posted by: "Robinson, Chad" > > Larry Bowen wrote: > > > > The fuse/breaker would provide protection. Would it not? > > Lyle Peterson wrote: > > Depends on which side is fused or breakered (is that a word?) If the > postive side is fused it would protect it. If the problem is one of > wiring the switch only to the negative side for some reason, I am > guessing that the same reasons apply to the fuse or breaker. > That means the fuse would be in the negative side and little or no > protection. On the other hand, one would probably not be wiring a negative-switched device into one's standard fuse panel, that being a 12V source itself. So Larry, unless you're looking to create a separate fuse panel of all NEGATIVE switched devices, I assumed you meant that you'd have an inline fuse or breaker upstream of this negative-switched device (that is, on the supply side). Is this the case? Because Lyle is right - wherever you put the switch, the FUSE should be on the supply side no matter what. And if your breaker IS your switch, then this is not a great idea. However, I'd like to restate my point that switch/breaker location is a bigger issue in systems where the voltage is not so fun to touch - a human can die from mains voltage without ever tripping a standard 20A breaker. Therefore, you always want a way to cut off the supply side as close to the source as possible, and so the breaker is ALWAYS on the hot side. My $0.00002c. =) Regards, Chad PS - None of my dictionaries (all relatively new, FWIW) contain "breakered" as an acceptable form of "breaker". However, LOTS of electrical supply and products companies like to use it, so I say what the heck, if the people you're talking to understand what you mean...