---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 04/04/06: 9 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:42 AM - Re: OVM nuisance trips during engine start (Ken) 2. 07:10 AM - Re: Z-13 Component Locations for RV-7 (Robert L. Nuckolls, III) 3. 12:03 PM - Re: Why use starter contactor? (Robert L. Nuckolls, III) 4. 12:56 PM - intercom ground loop? (Mickey Coggins) 5. 01:45 PM - Re: OVM nuisance trips during engine start (Robert L. Nuckolls, III) 6. 05:19 PM - B&C SD 8 alternator (Chris Hukill) 7. 07:39 PM - Re: power for headsets (James Freeman) 8. 08:00 PM - Re: power for headsets (Alan K. Adamson) 9. 08:28 PM - Re: B&C SD 8 alternator (Hinde, Frank George (Corvallis)) ________________________________ Message 1 _____________________________________ Time: 06:42:23 AM PST US From: Ken Subject: Re: AeroElectric-List: OVM nuisance trips during engine start --> AeroElectric-List message posted by: Ken Thank you for your thoughts Bob. I considered adding a diode in series with the 392 R resistor to pull up the reference voltage quicker but discarded the idea. I was thinking that while the voltage was rising immediately after cranking, such a diode would give the trigger voltage a 0.6 volt headstart so to speak. As you point out though that doesn't matter if the reference voltage doesn't sag in the first place. Have to check again but I think I'm just barely seeing over 12 volts at the time that I start cranking so not much headroom to bring the ref. voltage up to 12 volts before cranking. Maybe there's a schottky type diode in my junk pile... er..parts bin. This is an EFI engine so it does not normally need much cranking. I will try this diode on one of the OVM's this morning but it will take awhile before I know whether it does the trick. My analog scope is not the greatest tool for capturing one shot transients. I've been searching for a low cost portable or laptop DSO for the last couple of days as I'd also like some proof that my ignition is not occasionally missing a beat. There are a couple of offerings that seem like they might be useful in the $200 to $400. range. The megasquirt backup fuel injection that I'm using has datalog capability to a laptop and that is opening my eyes a bit to how useful digital recording can be. Ken Robert L. Nuckolls, III wrote: >--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > >At 12:23 PM 4/3/2006 -0400, you wrote: > > > >>--> AeroElectric-List message posted by: Ken >> >>Well now that I also have some hours on the engine and am on record as >>saying that nuisance OVM trips should not be tolerated, I must report >>that I am experiencing an OVM crowbar trip about every 10 th start or >>start attempt. This is a 12 volt Z-14 with small AGM batteries that >>parallel during cranking. Usually both homebuilt OVM's trip. If they >>trip it is usually on the first start (or start attempt) of the day and >>then no more on that day. >> >>My theory is that the cranking voltage is sagging way below the 12 volt >>zener and dragging the reference voltage down faster than it is dragging >>down the trigger voltage. (The time constant of the trigger circuit is >>higher than the time constant of the RC reference filter) My first >>inclination was to just add a lot of capacitance across the zener, >>especially since I haven't upgraded my 4.7 uF cap there to the 22 uF >>that is shown on the latest revision. However that would mean that after >>cranking ceases, the rising voltage would drive up the trigger voltage >>faster than the reference voltage and again possibly cause a trip. I am >>planning to try an intermediate experiment with a 68uF cap just for love >>of an experiment on one of the OVMs. >> >> > > Ken, thank you for sharing this with us. Another thing to > consider is putting a diode in series with the 392 ohm > resistor. This will keep the momentary brown-out spike from > pulling down on the capacitor during the transient. > > > > >>I think the best solution however is to use a lower voltage zener >>perhaps 8 or 9 volts and adjust the appropriate resistor values. I >>believe that would tend to make the circuit imune to low 8 or 9 volt >>cranking voltages and still retain acceptable accurancy. After all the >>24 volt version uses a 12 volt zener and I suspect it is imune to this >>type of tripping?? I plan to do that on at least one of my OVM's and >>will report the results. The engine cranks briskly and has fairly short >>starter wires. The cranking voltage does drop enough to cause my EIS4000 >>engine monitor to reset however. >> >> > > Have you ever put a 'scope on it to find out how low it > goes? It would be interesting to know. Also, since I'm > phasing out the MBS4991 trigger diode for all future > production, I have an inventory that I'm going to offer > for those who would like to fabricate the original circuit > that was not plagued with the phenomenon you've identified. > > In any case, I think your analysis has merit and adding the > diode would break the pull-down path during brownout time. > > Bob . . . > > > ________________________________ Message 2 _____________________________________ Time: 07:10:43 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Z-13 Component Locations for RV-7 --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 08:01 PM 3/27/2006 -0800, you wrote: >--> AeroElectric-List message posted by: "PIAVIS" > >I'm starting to figure out where all the components for the Z-13 system get >located in my RV-7. I'm tempted to have everything except the main current >limiter and the battery/starter contactors on the hot side of the firewall, >with everything else on the cold side. Is this how most have installed the >system? Not sure what you mean by "everything" . . . As a general rule, battery contactors mount as close as practical to batteries. Starter contactors as close as practical to starters. Place other equipment items so as to minimize the numbers of wires passing through the firewall. Bob . . . < What is so wonderful about scientific truth...is that > < the authority which determines whether there can be > < debate or not does not reside in some fraternity of > < scientists; nor is it divine. The authority rests > < with experiment. > < --Lawrence M. Krauss > ________________________________ Message 3 _____________________________________ Time: 12:03:49 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: Why use starter contactor? --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 11:18 AM 1/27/2006 -0600, you wrote: >--> AeroElectric-List message posted by: "Dave Morris \"BigD\"" > > >At 09:59 AM 1/27/2006, you wrote: > > > >If you > >get in a crash and the engine is ripped off, I don't think the battery > >cable will be you only problem. George > > > >It may not be, but it could mean the difference between walking away doused >in gasoline, and walking away on fire, hoping somebody can get to you >quickly enough to put out the flames. > >This happened to a friend of mine who would have walked away from a crash >if it had not been for that one little spark. I'm putting a starter >contactor on the firewall to absolutely shut off any possibility of the fat >wire going to the starter chafing against baffling material or anything >else in the event the engine decides to leave its normal upright, and >locked position. > >What's a few bucks, guys? My experience with this friend of mine has made >me a believer in steel braided fuel hose, Earl's fittings, Nomex clothing, >and a lot of other things that may cost a few dollars extra, but could >avoid years of skin graft surgery. The external contactor has nothing to do with crash safety. We recommended an external starter contactor for use with ALL starters having modern automotive style contactor/engagement solenoids. This policy was adopted by B&C from day-one in spite of the fact that their new light-weight offering already had a "useful" contactor built in. The reasoning was based on starter's need for a low impedance path between battery and the solenoid winding for energetic engagement of pinion gear and max performance closure of the built in contactor mechanism. The reason for this is explained at: http://aeroelectric.com/articles/strtctr.pdf The external contactor recommended is MUCH less abusive of the starter switch. Failure of many starter manufacturers to recognize this stress is root cause of premature failures of the ACS off-l-r-both-start ignition switch of some years back when an AD was issued to replenish the start switch contacts within the switch and to add a diode across the switch to mitigate inductive effects for breaking the circuit. The original AD placed the diode in the wrong place as I've described in . . . http://aeroelectric.com/articles/spikecatcher.pdf A later edition of the AD corrected the error and repositioned the diode. The diode only mitigates the switch-break-spike condition, not the switch-make-inrush condition. The larger than usual inrush is still present and is still a life limiting effect on the ACS or any other style switch. When PM starters came along, the wiring techniques recommended by B&C and the 'Connection were not compatible with starter motors which generated strong energies during wind-down and caused undesirable delays in pinion gear engagement. This is what prompted Figure Z-22 of http://aeroelectric.com/articles/Rev11/AppZ_R11F.pdf where a boost relay is used to relived panel mounted starter switches of the stresses cited. Reasoning was that I'd much rather replace a $5 relay under the cowl than ANY switch on the panel, especially an off-l-r-both-start keyswitch. I'll stand by the recommendations for wiring as show in either Z-22 (boost relay) or any other Z-figure where and external contactor is shown. It's a system performance, service life and cost of ownership consideration. ------------------------------ Here's an excerpt from an earlier post . . . I am designing my electrical system very similar to Z-11 with the exception of the essential bus and a keyed starter. My new Lycoming engine came with an SkyTec starter so I assume I'll need to use a relay as shown in Z-14. Does this mean I don't need a starter contactor? Does this relay replace the contactor or is it additional to it? Thanks Matt A problem arises when the starter utilizes a permanent magnet motor. These motors are also efficient generators During spin-down of the motor after the starter is de-energized, the motor puts out a substantial amount of power sufficient to KEEP the pinion gear solenoid ENGAGED for several seconds after you release the pushbutton. The technique described in our wiring diagrams was developed as a compromise between maintaining good starter solenoid/contactor performance with a variety of starter switches. Problems with the philosophy didn't arise until the permanent magnet motor showed up. Again, we sought a solution that maintained performance of the starter's built in solenoid/contactor system that did not transfer the system's unique loads to the circuitry that controls the starter. Hence, the "boost" relay described in Figure Z-22. One COULD choose to use the boost relay with ANY of the modern, lightweight starters that feature electro-mechanically engaged pinion gears. This would move the ideal alternator b-lead feedpoint from a contactor on the firewall down to the main power terminal of the starter solenoid/ contactor assembly. ----------------------------------------- Bob . . . ________________________________ Message 4 _____________________________________ Time: 12:56:09 PM PST US From: Mickey Coggins Subject: AeroElectric-List: intercom ground loop? --> AeroElectric-List message posted by: Mickey Coggins My flightcom 403 intercom has a ground wire, and the case itself is grounded. Will I be creating a ground loop if the case itself is grounded to the airframe via the panel? Should I try to isolate the intercom from the panel? Thanks, -- Mickey Coggins http://www.rv8.ch/ #82007 finishing do not archive ________________________________ Message 5 _____________________________________ Time: 01:45:50 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: OVM nuisance trips during engine start --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 09:14 AM 4/4/2006 -0400, you wrote: >--> AeroElectric-List message posted by: Ken > > Thank you for your thoughts Bob. > >I considered adding a diode in series with the 392 R resistor to pull up >the reference voltage quicker but discarded the idea. I was thinking >that while the voltage was rising immediately after cranking, such a >diode would give the trigger voltage a 0.6 volt headstart so to speak. >As you point out though that doesn't matter if the reference voltage >doesn't sag in the first place. Have to check again but I think I'm just >barely seeing over 12 volts at the time that I start cranking so not >much headroom to bring the ref. voltage up to 12 volts before cranking. >Maybe there's a schottky type diode in my junk pile... er..parts bin. >This is an EFI engine so it does not normally need much cranking. I will >try this diode on one of the OVM's this morning but it will take awhile >before I know whether it does the trick. I don't think there's an issue with how fast the ref voltage comes up, we just want to keep it from being pulled down during the locked-rotor inrush current that every starter imposes on a battery for the first few milliseconds while the motor is spinning up. See: http://www.aeroelectric.com/Pictures/Curves/99_Saturn_SL1.jpg Here we see bus voltage dipping to 7.5 volts and it takes about 600 mS before the voltage rises above 12v. All during this time, vref in the ov module is going to be something lower than 12v. 392 ohms and 22uf has a time constant of 8.6 milliseconds; the brownout interval is significantly longer. http://www.aeroelectric.com/Pictures/Curves/99_Saturn_SL1_2.gif This is a tighter view that shows the slope of the voltage during starter spin-up. There's no 'load' on Vref, it's a sinking reference that's keeping the ref point from rising at trip time. The only reason for the 392 resistor is to bias the zener into a low impedance region of relatively stable voltage. You could replace the 392 ohm resistor with something much higher and also make the 'problem' go away . . . but Vref will fall slightly with the lower bias current and have a slight effect on setpoint stability. I think the diode in series is the best bet. A 1N4000 series would be fine . . . or a 1N4148/914 would work good too. What ever you can put your hands on easiest. >My analog scope is not the greatest tool for capturing one shot >transients. I've been searching for a low cost portable or laptop DSO >for the last couple of days as I'd also like some proof that my ignition >is not occasionally missing a beat. There are a couple of offerings that >seem like they might be useful in the $200 to $400. range. The >megasquirt backup fuel injection that I'm using has datalog capability >to a laptop and that is opening my eyes a bit to how useful digital >recording can be. You got that right. I beat that drum every chance I get at RAC. We've been able to walk up to a $30,000 car for 20 years, plug in and have it spill it's guts. We STILL can't do that on a $5-$20 million bizjet's systems. Keep an eye on ebay for a TDS-210 scope. GREAT value. Even at new prices, the TDS-210 cost 1/2 of the first good scope I ever owned and it does 10 times as much. If the tornado sirens go off while I'm at the bench, the TDS-210 goes with me to the 'fraid-hole with me. Bob . . . ________________________________ Message 6 _____________________________________ Time: 05:19:23 PM PST US From: "Chris Hukill" Subject: AeroElectric-List: B&C SD 8 alternator --> AeroElectric-List message posted by: "Chris Hukill" Has anyone installed the B&C SD8 alternator on the RV10? I am trying to determine if there is any interference problems with the firewall. Thanks for any info. Chris Hukill ________________________________ Message 7 _____________________________________ Time: 07:39:36 PM PST US From: James Freeman Subject: Re: AeroElectric-List: power for headsets --> AeroElectric-List message posted by: James Freeman On Apr 1, 2006, at 8:33 AM, Mickey Coggins wrote: > --> AeroElectric-List message posted by: Mickey Coggins matronics@rv8.ch> > > I'm about to install the headset and mic jacks, and I'm > wondering if there is an "industry standard" way to > provide power for ANR type headsets. I've got the > Bose, and they want USD 31 for a special jack, and > USD 195 for the new headset cord. That would buy > a lot of batteries. > > Is there a better way? > > Thanks! > -- > Mickey Coggins > http://www.rv8.ch/ > #82007 finishing > Mickey--the Bose (a.k.a. "Redel") connectors are rapidly becoming a de facto standard in new factory GA aircraft. I have flown or ridden on four fixed-wing aircraft and two helicopters built since '03 and all had the "bose" connectors paralleled to the old standard headset jacks. They work fine in parallel, and you can mix and match headsets on then intercom. When I fly the Cirrus, I use Telex ANR headsets with the new connector, and I usually use an old Bose headset in the RV with a battery pack. As I type this, I have two of the Bose connectors sitting on my desk, waiting for a rainy day to install them in the RV-8. All of the headset manufacturers (Bose, Telex, Lightspeed, and Peltor at least) will sell a headset wired this way. If you can build an airplane, you can install the connector yourself. You could also buy a female plug like the one in the battery pack for your Bose and wire that for power (If you have the old ones with a separate battery pack) James ________________________________ Message 8 _____________________________________ Time: 08:00:19 PM PST US From: "Alan K. Adamson" Subject: RE: AeroElectric-List: power for headsets --> AeroElectric-List message posted by: "Alan K. Adamson" one note on this. I believe the DC also uses a similar jack - HOWEVER, there are 8 pin and 6 pin. To my knowledge, only DC uses the 8. Everyone else uses the 6 (better known as the Bose connector). Alan -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of James Freeman Sent: Tuesday, April 04, 2006 10:34 PM Subject: Re: AeroElectric-List: power for headsets --> AeroElectric-List message posted by: James Freeman On Apr 1, 2006, at 8:33 AM, Mickey Coggins wrote: > --> AeroElectric-List message posted by: Mickey Coggins matronics@rv8.ch> > > I'm about to install the headset and mic jacks, and I'm wondering if > there is an "industry standard" way to provide power for ANR type > headsets. I've got the Bose, and they want USD 31 for a special jack, > and USD 195 for the new headset cord. That would buy a lot of > batteries. > > Is there a better way? > > Thanks! > -- > Mickey Coggins > http://www.rv8.ch/ > #82007 finishing > Mickey--the Bose (a.k.a. "Redel") connectors are rapidly becoming a de facto standard in new factory GA aircraft. I have flown or ridden on four fixed-wing aircraft and two helicopters built since '03 and all had the "bose" connectors paralleled to the old standard headset jacks. They work fine in parallel, and you can mix and match headsets on then intercom. When I fly the Cirrus, I use Telex ANR headsets with the new connector, and I usually use an old Bose headset in the RV with a battery pack. As I type this, I have two of the Bose connectors sitting on my desk, waiting for a rainy day to install them in the RV-8. All of the headset manufacturers (Bose, Telex, Lightspeed, and Peltor at least) will sell a headset wired this way. If you can build an airplane, you can install the connector yourself. You could also buy a female plug like the one in the battery pack for your Bose and wire that for power (If you have the old ones with a separate battery pack) James ________________________________ Message 9 _____________________________________ Time: 08:28:42 PM PST US Subject: RE: AeroElectric-List: B&C SD 8 alternator From: "Hinde, Frank George (Corvallis)" --> AeroElectric-List message posted by: "Hinde, Frank George (Corvallis)" It works on the 7 and come to think of it, as this is where you would fit the standard (read God awful) vacuum pump I can't see why it would not fit. Frank Do not archive -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Chris Hukill Sent: Tuesday, April 04, 2006 5:14 PM Subject: AeroElectric-List: B&C SD 8 alternator --> AeroElectric-List message posted by: "Chris Hukill" --> Has anyone installed the B&C SD8 alternator on the RV10? I am trying to determine if there is any interference problems with the firewall. Thanks for any info. Chris Hukill