AeroElectric-List Digest Archive

Sun 08/24/08


Total Messages Posted: 7



Today's Message Index:
----------------------
 
     1. 07:22 AM - Re: Re: Tachometer Noise (Robert L. Nuckolls, III)
     2. 08:05 AM - Re: Printed circuits (Steve Stearns)
     3. 09:54 AM - Re: Printed circuits (Robert L. Nuckolls, III)
     4. 10:05 AM - Z diagram notes (rocket2man)
     5. 11:07 AM - Re: Z diagram notes (Robert L. Nuckolls, III)
     6. 11:16 AM - Re: Printed circuits (FOOEY) (Robert L. Nuckolls, III)
     7. 11:41 PM - Re: Search for Gremlins (F. Tim Yoder)
 
 
 


Message 1


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    Time: 07:22:56 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    Subject: Re: Tachometer Noise
    At 10:33 PM 8/23/2008 -0700, you wrote: > >The earlier Jabirus used a magnetic pickup at the ringear driving a VDO >tach / digital hourmeter and they later changed to the same pickup placed >near metal tabs on the flywheel (and different rpm calibration setting for >this) This is the normal way for larger diesel engines and the like. > >You are likely to have trouble using the alternator wires as source >because none of them connect to ground and the regulator will cause extra >pulses on the lines as it does its job. I do connect across the windings >and use a digital frequency counter for calibration of my other system, >and that works OK > >Ralph An excellent response Ralph. I've always been a bit mystified by some system designer's decisions to attempt a stable deduction of alternator fundamental frequencies when combined with a horrid mix of strong components of other noises! Then one must deal with belt/gearing ratios to scale the resulting signal to some number that represents real crankshaft RPM. The next worse signal source is magneto p-leads, but we've learned to deal with those to a reasonably successful degree. Mike, there ARE some things that could be tried which are something of a shot-in-the-dark. Without doing a lucid examination of the signals the tachometer is attempting to resolve, it's difficult to offer you a high-probability "fix". The absolutely best signal for tachometer success comes from some form of dedicated sensor. Magnetic, optical, closed contacts, etc. etc. But of course, these need to be added to an existing engine and one would really LIKE to get say 20 pulses per engine revolution for the easiest crafting of supporting electronics. The instability might be a function of levels, or as Ralph mentioned, the effects of extraneous stimulus from the voltage regulator. The fact that your instability happens at the higher RPMs suggest these causes as good candidates. If I were to take a 95% probability shot as suggesting some signal conditioning, I'd go for a band-pass filter (op amp and hand-full of jelly-bean parts) combined with a squaring section (over-driven op amp) as a means by which undesirable signals can be filtered out from the signal-of-interest. However, it MAY be that simple combinations of resistors, capacitors and perhaps some zener diodes would make your present combination useable using some parts from Radio Shack. Question: How much $time$ do you want or are willing to spend? We KNOW that your present system can be made to function as needed . . . but it MIGHT evolve into quite a 'science project'. If you're interested in expanding your knowledge base . . . particularly with a goal of sharing your discoveries with others and don't mind the $time$, I'm sure that I and others her on the List would be glad to give you suggestions. On the other hand, if you're driving toward first-light-under-the-wheels, perhaps a more conservative approach is indicated . . . an alternate pick-off scheme would be quick and a sure bet. Continue to search the web for situations where others have encountered the same problem and have discovered a 'fix'. If you don't get some encouragement from that effort, make the choice between doing a low-risk change of technologies -OR- exploring signal conditioning alternatives with the present setup. Are you an electron-chaser of any degree? Do you own or have access to a bench power supply, and perhaps a 'scope? Do you know from the VDO data what kind of signal the instrument expects to see? Since this system runs from a undetermined belt or gear ratio, does the instrument have some form of calibration pot? We'll need to know a lot more about the instrument itself to narrow down the range of techniques that could be applied to the problem. What's the VDO part number? Perhaps I or someone else can discover some useful things about this critter. One thing that would help is for me (or perhaps Ralph) to put our hands on the instrument. A few minutes on the bench would tell us what kind of pristine signal the tach likes to see and would put some bounds on the approach to crafting a useful filter. There's NOTHING that replaces NUMBERS to design to. I (and perhaps others on the List) have an interest in deducing a filter that would make your system work. But we could spend a lot of YOUR $time$ to make that happen and we're 100.0% sure of success. Only you are in a position to make the well considered choice. Bob . . .


    Message 2


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    Time: 08:05:40 AM PST US
    From: Steve Stearns <steve@tomasara.com>
    Subject: Re: Printed circuits
    Bob and group, Questions follow my personal experiences below: I've had good results with both 99% Rubbing Alcohol and commercial spray-on flux remover on common rosin flux. Whenever I use a traditional rosin flux solder (or solder wick for that matter) I clean it off completely. I've had bad experiences with water-soluble fluxes in the past and so avoid them like the plague (except, obviously, where mandated by a client's manufacturing operations). Although they may have gotten better in the recent years (to be replaced with problems related to RoHS, no doubt). In the past they were very demanding of very complete cleaning and, if not cleaned completely, tended to enable the slow "growth" (metallurgically speaking, not biologically speaking) of a white fuzz the was conductive and which resulted in field failures one or more years after ship (this is going back to the late eighties, however, and may be irrelevant with todays products). I'm dreading the re-appearance of this kind of problem with tin growth once our solder and parts have been purged of the dreaded lead that was so helpful in controlling this problem. My current flux-of-choice is Kestor's No-Clean flux and, per Kestor, I don't remove it. However, I have found if I try to remove it with the same chemicals used for rosin flux, I can get white residue (which I view with great suspicion). Last I looked (a couple of years ago) Kestor's web-site had a white paper on this issue which (as I remember) basically concluded by not recommending any flux remover for this flux and by recommending re-fluxing and re-heating to get rid of the white stuff. In conclusion, I pay great attention to which flux I wish was removed before deciding on a course of action. My questions: How do other's in this group deal with "no-clean" fluxes? How important is it to clear-coat boards (I assume this greatly helps when in a condensing atmosphere but I don't have experience with this process)? Can you clear-coat over "no-clean" flux or must it be removed? Thanks in advance for your thoughts, Steve Stearns Boulder/Longmont, Colorado CSA,EAA,IAC,AOPA,PE,ARRL,BARC (but ignorant none-the-less) Restoring (since 1/07): N45FC O235 Longeze Cothern/Friling CF1 (~1000 Hrs) Flying (since 9/86): N43732 A65 Taylorcraft BC12D


    Message 3


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    Time: 09:54:27 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    Subject: Re: Printed circuits
    At 09:04 AM 8/24/2008 -0600, you wrote: > >Bob and group, > >Questions follow my personal experiences below: > >I've had good results with both 99% Rubbing Alcohol and commercial >spray-on flux remover on common rosin flux. Whenever I use a traditional >rosin flux solder (or solder wick for that matter) I clean it off completely. Yes, those are what I've referred to as "plastic" fluxes. Originally real tree-rosin, modern encarnations are synthetic but no less messy when the hard work (make it function) is done. >I've had bad experiences with water-soluble fluxes in the past and so >avoid them like the plague (except, obviously, where mandated by a >client's manufacturing operations). Although they may have gotten better >in the recent years (to be replaced with problems related to RoHS, no >doubt). In the past they were very demanding of very complete cleaning >and, if not cleaned completely, tended to enable the slow "growth" >(metallurgically speaking, not biologically speaking) of a white fuzz the >was conductive and which resulted in field failures one or more years >after ship (this is going back to the late eighties, however, and may be >irrelevant with todays products). I'm dreading the re-appearance of this >kind of problem with tin growth once our solder and parts have been purged >of the dreaded lead that was so helpful in controlling this problem. Right on. My all time favorite solder is Kester Resin 44 that I've stockpiled to a lifetime supply. It flows well, fluxes well, and yes . . . it demands some attention to cleaning when you're all done. >My current flux-of-choice is Kestor's No-Clean flux and, per Kestor, I >don't remove it. However, I have found if I try to remove it with the >same chemicals used for rosin flux, I can get white residue (which I view >with great suspicion). Last I looked (a couple of years ago) Kestor's >web-site had a white paper on this issue which (as I remember) basically >concluded by not recommending any flux remover for this flux and by >recommending re-fluxing and re-heating to get rid of the white stuff. Interesting! I've not experienced this stuff first hand. I think one of my clients uses it on their hand-assembly line. I'll inquire as to their post- assy processes. The flux used on their pick-n-place line is water soluble. This stuff is removed by an expensive "dish washer" with some kind of proprietary surfactants (probably dish soap). They DO come out very clean and read to conformal coat. >In conclusion, I pay great attention to which flux I wish was removed >before deciding on a course of action. Sounds like a folk who's been-there-done-that. >My questions: How do other's in this group deal with "no-clean" fluxes? >How important is it to clear-coat boards (I assume this greatly helps when >in a condensing atmosphere but I don't have experience with this process)? I've never been tasked with crafting that process but I'll ask around. I don't think anyone in production uses a no-clean flux. There are just too many contaminant and surface prep issues for coating that make post-solder cleaning a really big issue. I was told by a Kester rep many moons ago that the whole idea behind no-clean flux was that it didn't leave reactive contaminants behind . . . at least reactive at normal operating temperatures and humidity. Obviously, to be a good flux it had to be very reactive at solder temperatures. >Can you clear-coat over "no-clean" flux or must it be removed? That's what they told me . . . but it still LOOKED like @!#@@#@$. That's why I've never embraced these materials personally. Good ol' "44" and some moderately strong solvents have served me and my sense of craftsmanship well for decades. >Thanks in advance for your thoughts, You've raised some interesting questions. I'll see what my friends in the industry can offer. In the mean time, check out this resource at: http://www.kester.com/en-us/datasheets/ds_dirdetail.aspx?location=Fluxes This suite of products goes back at least 50 years and includes the present offerings from Kester. Bob . . .


    Message 4


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    Time: 10:05:36 AM PST US
    From: rocket2man <rocket2man@isp.com>
    Subject: Z diagram notes
    Bob - I'm working to provide more details for my RV8 electrical issue. The "Z wiring diagram" I have for my airplane have "notes" indicated on the drawing. Where do I find these? Thank you. JBB


    Message 5


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    Time: 11:07:43 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    Subject: Re: Z diagram notes
    At 10:04 AM 8/24/2008 -0700, you wrote: > >Bob - >I'm working to provide more details for my RV8 electrical issue. The "Z >wiring diagram" I have for my airplane have "notes" indicated on the >drawing. Where do I find these? Thank you. JBB http://aeroelectric.com/articles/Rev11/AppZ_R11M.pdf Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ----------------------------------------


    Message 6


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    Time: 11:16:22 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    Subject: Re: Printed circuits (FOOEY)
    At 11:52 AM 8/24/2008 -0500, you wrote: > You've raised some interesting questions. I'll see > what my friends in the industry can offer. In the > mean time, check out this resource at: > >http://www.kester.com/en-us/datasheets/ds_dirdetail.aspx?location=Fluxes > > This suite of products goes back at least 50 years > and includes the present offerings from Kester. Correction. I did find some posted data sheets on Resin "44" as a flux . . . thought it was Kester's site but I guess not. The link posted above is for current production offerings only. Still a good reference for how "water soluble", "no-clean" etc should perform. Bob . . .


    Message 7


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    Time: 11:41:48 PM PST US
    From: "F. Tim Yoder" <ftyoder@yoderbuilt.com>
    Subject: Re: Search for Gremlins
    With the success of the test of running a new ground wire from the oil pressure gauge to the engine case, that removed the wiggle when I activated the Alt., I did as you suggested and ran a new fat - ground wire (8 gauge) from the engine case to the ground block. I then removed the original engine to motor mount jumpers and temporary oil pressure ground wire. I started the engine and wiggle came back. DRATS! I then removed all the ground wires from the ground block, cleaned the blocks and re installed the grounds. O/P needle still wiggles in the same way. The only part of the system I haven't checked is the battery which is located behind the baggage compartment, I planed to do that this week. If this report leads you to any other suggestions I will certainly appreciate them. Tim ---- Original Message ----- From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net> Sent: Monday, August 18, 2008 7:17 AM Subject: Re: AeroElectric-List: Search for Gremlins <nuckolls.bob@cox.net> > > At 11:47 PM 8/17/2008 -0400, you wrote: > > > >8/17/2008 > > > >To reply to the author, write to "F. Tim Yoder" <ftyoder@yoderbuilt.com> > > > >Report on this weekends search for Gremlins; > > > >I spent several hours under the panel checking all the ground buss > >connections, breaker and switch grounds. I loosened the connections to the > >amp, volt, oil temp and oil pressure gauges, wiggled the terminals and re > >tightened. I did the same thing to the alternator and removed the regulator > >spades and replaced them.I removed the radio, cleaned the connectors and re > >installed it. I checked the ground straps from the engine to the motor > >mount. I spent some time looking for something,anything wrong. > > There should be no ground straps from engine to motor mount. Only > one fat-wire jumper from crankcase to your single-point ground on > the firewall. > > > >I started the plane and found that I had not ran off any Gremlins. When I > >turn on the Alt. the oil pressure dropped from 75# to 60# then settled on > >70#, this takes about one second. As soon as I turn off the Alt. the oil > >pressure goes back to 75#. With the radio and Alt. on the oil pressure > >needle drops a needle width when I key the radio. Again, with the Alt. off > >keying the radio does not effect the oil pressure gauge which was back to > >75#. > > > >I did not fly so I didn't have any radio issues. I think I need to find the > >cause of the apparent load on the oil pressure gauge first. > > It sounds like a ground loop issue driven by too much resistance > between crankcase and the oil pressure instrument ground. Try > removing the existing ground wire for the instrument and > grounding the instrument directly to the crankcase. > > If this makes the wiggle go away, I'll suggest you remove all > jumpers from engine to mount and add one fat-jumper between > crankcase and ground block. > > > >Oh, the Amp. meter is a little positive at idle and the voltage is showing > >a charge of about 14.4V and 13.5V with at Alt. off. > > Those numbers are right in the ballpark. > > > >I'll appreciate any suggestions. > > > >Thanks again, Tim > > Bob . . . > > ----------------------------------------) > ( . . . a long habit of not thinking ) > ( a thing wrong, gives it a superficial ) > ( appearance of being right . . . ) > ( ) > ( -Thomas Paine 1776- ) > ---------------------------------------- > >




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