---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 12/16/11: 12 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:27 AM - Re: Purpose of Diodes on Relays (Robert L. Nuckolls, III) 2. 07:11 AM - Re: Use of non-aviation Ford-style regulators (Robert L. Nuckolls, III) 3. 09:22 AM - Relay protection diodes. (Victor Menkal) 4. 09:22 AM - Re: Re: Auto Aux Fuel Pump Circuit Idea (Robert L. Nuckolls, III) 5. 10:42 AM - Re: Purpose of Diodes on Relays (rayj) 6. 11:22 AM - Vans 35A alternator - Nippondenso 14184 (Peter Mather) 7. 11:31 AM - Re: Purpose of Diodes on Relays (Noel Loveys) 8. 01:32 PM - Re: Purpose of Diodes on Relays (Robert L. Nuckolls, III) 9. 01:43 PM - Re: Auto Aux Fuel Pump Circuit Idea (Fred Stucklen) 10. 01:49 PM - Re: Vans 35A alternator - Nippondenso 14184 (Robert L. Nuckolls, III) 11. 02:02 PM - Re: Purpose of Diodes on Relays (Robert L. Nuckolls, III) 12. 02:52 PM - Re: Vans 35A alternator - Nippondenso 14184 (Peter Mather) ________________________________ Message 1 _____________________________________ Time: 06:27:54 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Purpose of Diodes on Relays At 11:26 PM 12/15/2011, you wrote: I noted that the manufacturer of my ignition switch requests a diode across the between the excitation (low current start switch) input and ground. Also noted that Bob calls out diodes on fig Z-16 wiring diagram for the Rotax 912. Can anyone provide a simple explanation of reason for these? As well Bob did not call out the diode on Z-16 but assume its the same as the other drawings which calls for a 1N5400 diode. Capacitors and inductors are both capable of 'storing energy'. Capacitors store charge as a voltage which manifests when electrons pile up in the insulating space between two conductors. Discharging a capacitor offers potential for a very high current event. Inductors store a charge in their magnetic fields. While current is flowing from external sources, a field is generated within the core of the inductor. When that external source is removed, the magnetic field collapses rapidly. Voltage generated in the windings of the inductor is proportional to the number of turns, strength of the field and RATE OF CHANGE for the collapse of that field. The diodes shown wired in parallel with the coils of relays and solenoids to effect an orderly management of that stored energy. See . . . http://www.aeroelectric.com/articles/spikecatcher.pdf We've had some past discussions here on the List about the 'optimal' choice of components for managing this energy. The confusion has been compounded by erroneous notions published over the signatures of people who should have known better. Suffice it to say that for OUR purposes in the crafting systems with exceedingly low service cycles . . . the plain vanilla diode approach illustrated in my drawings suffices nicely. Here's a capture of one such discussion thread where I attempted to apply some simple-ideas in physics with practical recipes for success in the art of 'spike management' . . . http://www.aeroelectric.com/articles/spike.pdf Know also that good management of this energy does NOT go to the PROTECTION of solid state devices in the ship's systems. It's for protection of service life on the controlling device. I.e., diode on the battery contactor improves on the service life of the battery master switch. Suppression of this transient also goes to minimizing the probability of interference with other systems . . . which is a transient performance event, not a destructive event. ANY diode is capable of doing the job electrically. I recommend the 1N5400 series devices for their robust MECHANICAL qualities. But the actual part number is electrically non-critical. I really like Bob's crow bar over voltage module and alternator disconnect relay which is not included in the standard Rotax wiring schematic. Low cost and easy to install (following Bob's schematic of course) and covers off one problem area which a number of Rotax owners have identified with the standard wiring system and rectifier. Best part is that my ALT switch on the panel is now gainfully employed (not used following standard Rotax diagram). Over voltage protection option is also highly recommended by the Rotax guru's at Rotec Research Canada. I have not been made aware of any runaway alternator situations with the PM alternators. A rectifier/regulator is: (1) an electrical device that HAS runaway failure modes and(2) is highly stressed - runs hotter than !@#$@#. OV protection seems a prudent addition to the stock drawings supplied by engine manufacturers which never seem to include OV protection recommendations. We theorized here on the List that the public relations types for the various engine suppliers would be embarrassed to admit that their product offering could fail in a very unhappy manner. Hence, "let us not admit it by recommending ov protection." Bob . . . ________________________________ Message 2 _____________________________________ Time: 07:11:04 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Use of non-aviation Ford-style regulators Paul Millner wrote: Note that it can be dangerous to use non-aviation Ford-type regulators in our airplanes. When the alternator half of the master switch is turned off, the regulator will allow the alternator to go into a voltage runaway mode, and that overvoltage will not be controlled by your overvoltage relay (since the field current is flowing via a separate path, directly from the alternator). The overvoltage condition can cook your avionics and battery. Even if you don't turn off the alternator half of the master switch, if your separate overvoltage relay trip for any reason with such a regulator installed, that, ironically, will trigger the voltage runaway scenario. Paul At 07:02 PM 12/15/2011, you wrote: Uh oh. What's the protection for this? I'm using not a Ford, but a smaller, denser, lighter Japanese alternator with same output. David Merchant Man! I've not had occasion to lift the lid on this pot of stew since I owned the Benton Airpark (1K1) 22 years ago. Paul's admonition arises from the fact that SOME solid state replacements for the original Ford electromechanical regulators do not conform to the form, fit and function of those regulators. As installed first on automobiles the Ford style regulator was configured thusly: Emacs! The regulator contained two "relay" like devices wherein one relay was the voltage regulator and the second was used as an ON-OFF control of field excitation. The field relay sensed a DC voltage on the alternator's "N" terminal (y-wound stator center tap) and would automatically excite an alternator as soon as the engine was started and the alternator was demonstrated to be in motion. This all happened through a tiny excitation current that would flow through the alternator warning light bulb into the regulator's "I" or indicator terminal. Failure of this light bulb led to a lot of regulators and alternators being swapped out as mechanics who did not understand the system tried to get their customer's car back on the road. Later systems added a resistor across the lamp to make sure that the alternator would still come on line even if the bulb were burned out. This is the root-system from which Cessna's alternators evolved. Cessna chose to run their field supply voltage right into the "A" terminal and control the field supply relay directly with alternator field switch controlling the "S" terminal. In later years, the OV protection module (first proposed by yours truly) was inserted between the alternator field switch and the "S" terminal. Emacs! So much for the history. In later years, solid state replacements with the same A, S, I and F terminal markings were crafted where the S-terminal was no longer used for field control but for BUS VOLTAGE SENSING. When one drops one of these regulators into an automobile, the system still performs in a useful manner. When dropped into a Cessna, opening the field control side of the split master switch deprived the regulator of control information causing the alternator to full-field . . . i.e. OV runaway. I'm not sure that ALL solid state drop-ins for a Ford regulator behave in this manner . . . but some do. Been there, done that on one of my rental fleet airplanes. But if "Ford-style" regulators are wired per recommendations in the Z-figures (A and S terminals tied together) there is no risk for experiencing the design induced runaway condition. Bob . . . ________________________________ Message 3 _____________________________________ Time: 09:22:19 AM PST US From: Victor Menkal Subject: AeroElectric-List: Relay protection diodes. Thanx David. I think I found the reason for the diodes is to protect electronics from the brief high voltage spike created in the relay coils when the relay is switched off. Appreciate advice if a 1N5400 diode (3A 100V) is ok for the master relay. Thanx Vic Vic Menkal CH750 Rotax 912ULS Whitehorse Yukon ________________________________ Message 4 _____________________________________ Time: 09:22:19 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Auto Aux Fuel Pump Circuit Idea At 09:59 PM 12/15/2011, you wrote: > > >I've given some more thought and testing on the Auto Aux Fuel Pump >idea that I originally posted. I've attached a schematic of a >circuit I've bread boarded and tested. Seems to to work. > The idea/implementation is to automatically turn the pump ON for > as long as the fuel pressure is below a set limit, and don't turn > it off until the pressure has been above that limit for at least 10 > seconds. If the pressure go low again, the process is repeated. > I'm planning on making up a hardwired proto board and actually > testing in my RV-7A, but probably not until after the new year..... The circuit yields well to critical review but it took me a bit of feather-sorting to understand application of the power FET as drawn. You your schematic has the bulk connection tied to the drain terminal and the thing that jumped off the page at me was an N-channel FET. But after sorting out the S-G-D labels and application in the circuit, the real P-channel device emerged. Another approach worth considering is use of an N-Channel device as a pull-down switch. You'd need to do some re-wiring to make the pump's manual ops be pull-to-ground too. The N-channel offers potentially 1/10th the on-resistance of a P-channel. Heat sinking of the device becomes much easier and performance goes up with the reduced voltage drop. Bob . . . ________________________________ Message 5 _____________________________________ Time: 10:42:19 AM PST US From: rayj Subject: Re: AeroElectric-List: Purpose of Diodes on Relays On 12/16/2011 08:23 AM, Robert L. Nuckolls, III wrote: > > > Capacitors and inductors are both capable of 'storing > energy'. Capacitors store charge as a voltage which > manifests when electrons pile up in the insulating > space between two conductors. Discharging a capacitor > offers potential for a very high current event. Greetings, It's my understanding that the electrons accumulate in the conductor on one side of the insulating space while "holes" accumulate in the conductor on the other side of the insulating space. Clarification? Raymond Julian Kettle River, MN "And you know that I could have me a million more friends, and all I'd have to lose is my point of view." - John Prine > > Inductors store a charge in their magnetic fields. > While current is flowing from external sources, a > field is generated within the core of the inductor. > When that external source is removed, the magnetic > field collapses rapidly. Voltage generated in the > windings of the inductor is proportional to the number > of turns, strength of the field and RATE OF CHANGE > for the collapse of that field. > > The diodes shown wired in parallel with the coils > of relays and solenoids to effect an orderly management > of that stored energy. See . . . > > http://www.aeroelectric.com/articles/spikecatcher.pdf > > We've had some past discussions here on the List > about the 'optimal' choice of components for managing > this energy. The confusion has been compounded by > erroneous notions published over the signatures of > people who should have known better. Suffice it to > say that for OUR purposes in the crafting systems > with exceedingly low service cycles . . . the plain > vanilla diode approach illustrated in my drawings > suffices nicely. > > Here's a capture of one such discussion thread where > I attempted to apply some simple-ideas in physics > with practical recipes for success in the art > of 'spike management' . . . > > http://www.aeroelectric.com/articles/spike.pdf > > Know also that good management of this energy does > NOT go to the PROTECTION of solid state devices in > the ship's systems. It's for protection of service > life on the controlling device. I.e., diode on the > battery contactor improves on the service life of > the battery master switch. Suppression of this transient > also goes to minimizing the probability of interference > with other systems . . . which is a transient > performance event, not a destructive event. > > ANY diode is capable of doing the job electrically. > I recommend the 1N5400 series devices for their > robust MECHANICAL qualities. But the actual > part number is electrically non-critical. > > I really like Bob's crow bar over voltage module and alternator > disconnect relay which is not included in the standard Rotax wiring > schematic. Low cost and easy to install (following Bob's schematic of > course) and covers off one problem area which a number of Rotax owners > have identified with the standard wiring system and rectifier. Best part > is that my ALT switch on the panel is now gainfully employed (not used > following standard Rotax diagram). Over voltage protection option is > also highly recommended by the Rotax guru's at Rotec Research Canada. > > I have not been made aware of any runaway alternator > situations with the PM alternators. A rectifier/regulator > is: (1) an electrical device that HAS runaway failure > modes and(2) is highly stressed - runs hotter than !@#$@#. > OV protection seems a prudent addition to the stock > drawings supplied by engine manufacturers which never > seem to include OV protection recommendations. > > We theorized here on the List that the public relations > types for the various engine suppliers would be > embarrassed to admit that their product offering could > fail in a very unhappy manner. Hence, "let us not > admit it by recommending ov protection." > > > Bob . . . > > ________________________________ Message 6 _____________________________________ Time: 11:22:02 AM PST US From: "Peter Mather" Subject: AeroElectric-List: Vans 35A alternator - Nippondenso 14184 Can anyone tell me the purpose of the third wire on the connector of this alternator? The cable supplied by Vans has Black - ground; green - field; white - not connected. I'm looking at using a regulator that has a stator connection which it uses to drive an ignition light - is the white connection to the stator? Thanks in advance Peter ________________________________ Message 7 _____________________________________ Time: 11:31:15 AM PST US From: "Noel Loveys" Subject: RE: AeroElectric-List: Purpose of Diodes on Relays A starting motor is essentially a coil. When you activate the starter (read coil) draws down on the current of the battery. The more load on the starter the greater the current drawn by the starter. When you release the starter button, key or whatever, all the energy stored up in the coil (or starter motor) is immediately dumped into the circuit, with extremely high voltage in reverse polarity. The diode allows this reverse potential to be drained off safely without frying all your expen$ive avionics and other digital equipment on the buss. Clear as mud? Noel From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Victor Menkal Sent: December 16, 2011 1:56 AM Subject: AeroElectric-List: Purpose of Diodes on Relays I noted that the manufacturer of my ignition switch requests a diode across the between the excitation (low current start switch) input and ground. Also noted that Bob calls out diodes on fig Z-16 wiring diagram for the Rotax 912. Can anyone provide a simple explanation of reason for these? As well Bob did not call out the diode on Z-16 but assume its the same as the other drawings which calls for a 1N5400 diode. I really like Bob's crow bar over voltage module and alternator disconnect relay which is not included in the standard Rotax wiring schematic. Low cost and easy to install (following Bob's schematic of course) and covers off one problem area which a number of Rotax owners have identified with the standard wiring system and rectifier. Best part is that my ALT switch on the panel is now gainfully employed (not used following standard Rotax diagram). Over voltage protection option is also highly recommended by the Rotax guru's at Rotec Research Canada. Thanx Vic CH750 Rotax 912ULS-2 Whitehorse Yukon ________________________________ Message 8 _____________________________________ Time: 01:32:25 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Purpose of Diodes on Relays > >Greetings, > >It's my understanding that the electrons accumulate in the conductor >on one side of the insulating space while "holes" accumulate in the >conductor on the other side of the insulating space. > >Clarification? That's a good a analogy. Here are some explanations with a lot of mathematical description but one can clean the simple-ideas of the physics . . . http://en.wikipedia.org/wiki/Dielectric http://www.physics.sjsu.edu/becker/physics51/capacitors.htm Bob . . . ________________________________ Message 9 _____________________________________ Time: 01:43:17 PM PST US Subject: AeroElectric-List: Re: Auto Aux Fuel Pump Circuit Idea From: "Fred Stucklen" nuckolls.bob(at)aeroelect wrote: > At 09:59 PM 12/15/2011, you wrote: > > Bob, > > Yep, I guess I drew the MOSFET incorrectly. It is a "P" channel device. Power dissipation on this .02 ohm ON device should be minimal. So far testing has show that it can draw 10 amps with no heatsink.... I will heatsink it in the prototype. > I'd rather test the concept in a way that involves little change to the existing wiring in the plane. I currently have the circuit wired to switch the positive side, so the "P" Channel device works better for me. Very easy to change it to a pull down circuit if some one else wanted that method. > I think the next step is to prototype it, bench check it using an actual pump (instead of the halogen bulb I'm currently using for a load)and then begin actual flight testing of the timed concept. If this works out OK, it might be lower cost to implement the design using the PIC processor. > By the way, thanks for the proto board idea. I might use that in the future... > > Fred Stucklen > RV-7A N924RV 650 Hrs > > > The circuit yields well to critical review but it took me a bit of feather-sorting to understand application of the power FET as drawn. You your schematic has the bulk connection tied to the drain terminal and the thing that jumped off the page at me was an N-channel FET. But after sorting out the S-G-D labels and application in the circuit, the real P-channel device emerged. Another approach worth considering is use of an N-Channel device as a pull-down switch. You'd need to do some re-wiring to make the pump's manual ops be pull-to-ground too. The N-channel offers potentially 1/10th the on-resistance of a P-channel. Heat sinking of the device becomes much easier and performance goes up with the reduced voltage drop. Bob . . .[/quote] Read this topic online here: http://forums.matronics.com/viewtopic.php?p=361068#361068 ________________________________ Message 10 ____________________________________ Time: 01:49:11 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Vans 35A alternator - Nippondenso 14184 At 01:17 PM 12/16/2011, you wrote: > >Can anyone tell me the purpose of the third wire on the connector of this >alternator? > >The cable supplied by Vans has Black - ground; green - field; white - not >connected. > >I'm looking at using a regulator that has a stator connection which it uses >to drive an ignition light - is the white connection to the stator? Does Van's alternator REQUIRE an external regulator? Last time I looked, their offerings were internally regulated. Can you post an excerpt of the schematic . . . or point us to a link where your applicable schematic is visible? Trying to give useful advise based on numbers of pins and colors of wires is risky. The SCHEMATICS associated with the products being explored are necessary for offering well considered advice. Bob . . . ________________________________ Message 11 ____________________________________ Time: 02:02:43 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Purpose of Diodes on Relays At 01:28 PM 12/16/2011, you wrote: >A starting motor is essentially a coil. When you activate the >starter (read coil) draws down on the current of the battery. The >more load on the starter the greater the current drawn by the >starter. When you release the starter button, key or whatever, all >the energy stored up in the coil (or starter motor) is immediately >dumped into the circuit, with extremely high voltage in reverse >polarity. The diode allows this reverse potential to be drained off >safely without frying all your expen$ive avionics and other digital >equipment on the buss. A few years back (about 11) when we were exploring the behavior of energy stored on inductive devices, we discovered (and demonstrated on the bench) that un-suppressed spikes from inductive devices are almost totally dissipated across the spreading contacts of the switching device. For example, here's one of many plots we gathered while stirring the Contactor-Spike- Stew pot: http://www.aeroelectric.com/Pictures/Curves/CH_Bus_Noise_w_0p1_Cap.gif There are two traces. The top one shows voltage developed across the contacts of the controlling switch . . . the lower trace shows voltage that made it out to the bus . . . barely perceptible. Know that electronic devices designed to run directly from the bus of any vehicular DC system is (1) easily designed to stand off the (2) minuscule packet of energy that makes it across the opening switch. In short, there is no risk of "frying" anything. The major risk is shortened service life of the switch that controls the contactor. The same conditions apply to energy dumped from a starter motor . . . it's the starter contactor that takes the hit, not electro whizzies running off the bus. One might think that an inductor charged to hundreds of amps represents the grand dragon of spike generators. Motors have a unique feature called counter-emf. A 12v motor really runs on the DIFFERENCE voltage between applied voltage (battery) and counter-emf due to rotation. The real free inductance model of a motor is rather small in comparison with contactor coils having hundreds of turns of wire. This is why you never see spike suppressors on a motor . . . they're just not a potential threat. Bob . . . ________________________________ Message 12 ____________________________________ Time: 02:52:58 PM PST US From: "Peter Mather" Subject: RE: AeroElectric-List: Vans 35A alternator - Nippondenso 14184 Bob The alternator is one Vans were selling back in 04. It is externally regulated and Vans then recommended a VR-1751 or MS-150A regulator but always said to leave the white lead "unconnected" I can't see what else the third wire could be except a stator connection but any suggestions or test ideas would be appreciated. Best Regards Peter -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: 16 December 2011 21:42 Subject: Re: AeroElectric-List: Vans 35A alternator - Nippondenso 14184 --> At 01:17 PM 12/16/2011, you wrote: >--> > >Can anyone tell me the purpose of the third wire on the connector of >this alternator? > >The cable supplied by Vans has Black - ground; green - field; white - >not connected. > >I'm looking at using a regulator that has a stator connection which it >uses to drive an ignition light - is the white connection to the stator? Does Van's alternator REQUIRE an external regulator? Last time I looked, their offerings were internally regulated. Can you post an excerpt of the schematic . . . or point us to a link where your applicable schematic is visible? Trying to give useful advise based on numbers of pins and colors of wires is risky. The SCHEMATICS associated with the products being explored are necessary for offering well considered advice. 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