Matronics Email Lists :: View topic - Dan's Jabiru 3300 Wiring Schematic

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Dan's Jabiru 3300 Wiring Schematic
Goto page Previous 1, 2

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Aug 25, 2009 8:11 am Post subject: Dan's Jabiru 3300 Wiring Schematic

 	  Quote: 	
		  

Although the manual lists the magneto kill switch as a possible tach 

signal source, any fault in the signal wire would short out the 

magneto.  Who knows what affect the 10K ohm impedance of the RDAC VD 

would have on the ignition system?  Since the dynamo is integrated 

with the flywheel and generates AC voltage, it should provide the 

RPM signal.  It is worth a try.


	


   Resistances as low as a few hundred ohms will probably

   have no effect on ignition performance . . . the kill

   switch on magneto-type ignition systems generally places

   a dead short on a few turns of the spark voltage coil

   thus killing it's ability to function. This is a rather

   low impedance energy source and not easily "loaded"

   to the extent that the ignition fails. The biggest

   problem with getting tach data from ignition sources

   is the very trashy waveform that CAN be easily signal

   conditioned if the tach designer is aware of the

   signal's characteristics.



 	  Quote: 	
		  Bob said:

 > You show a tach signal off the AC widings of the altenrator.

 > This will not be useful with the alternator disconnect relay

 > open.

Bob, I do not understand this, since the tach signal wire is 

connected to the alternator side of the disconnect relay.  Doesn't 

the alternator continue to generator voltage whether there is a load 

on it or not?  Or does the regulator open the grounded alternator lead?


	


   The alternator leads go to a bridge rectifier's AC

   input poles . . . neither goes to ground.

   Availability of a predictable signal from the

   AC windings assumes that the system is producing

   power normally.  Now, there is SOME sort of signal

   present with the relay open . . . but its characteristics

   are different that for normal operation. The

   designer of the tachometer probably wasn't tasked

   with covering this case so useful operation becomes

   problematic.

        Bob . . .



         ---------------------------------------

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

messydeer

Joined: 13 Feb 2006
Posts: 214
Location: Bellingham, WA

Posted: Tue Aug 25, 2009 8:27 am Post subject: Re: Dan's Jabiru 3300 Wiring Schematic

Thanks, Joe 



I'd heard of getting a tach signal from the P-leads. This must be the same as what they talk about with the mags. And would have the same risks of grounding, I would think.



 	  Quote: 	
		  You show a tach signal off the AC widings of the altenrator. 

This will not be useful with the alternator disconnect relay 

open. 	




Here's my understanding: the alternator has two leads of AC coming out. With AC, one lead will have current go out, while the other has it come in (like a ground?). The leads switch every 180. So opening just one of the leads kills output, just like breaking a ground connection in a DC circuit.



It also seems that if I did get the tach signal here, then I would have a defacto open alternator disconnect relay alarm: no tach would mean relay open.

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

_________________
Dan

user9253

Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan

Posted: Thu Aug 27, 2009 6:46 pm Post subject: Re: Dan's Jabiru 3300 Wiring Schematic

I have taken a portion of Dan's schematic that pertains to the dynamo, regulator, and tachometer and simplified it in an attempt to better understand it.  I moved the bridge rectifier outside of the regulator.  And I added one more diode in series with the tach so that the tach only sees half of the dynamo waveform.  By adding this extra diode, I believe that the tach will see the same signal whether the alternator relay is pulled in or not, since the tach is connected in parallel with the dynamo through two diodes.  The dynamo frequency is dependent upon the engine speed since it is mounted onto the flywheel.  The output voltage will vary depending of the state of the disconnect relay and aircraft load.  However, the voltage should not affect the tach unless it drops below the minimum (2.5 to 5 volts) required.

   Bob, what do you think?  Will Dan's tach work as connected in his schematic if a diode is added in series with it?  Or do I have it all wrong?  And that could be, because I do not know what is inside of the regulator case.

Joe

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

tach.jpg

Description:

Filesize:

47.82 KB

Viewed:

4324 Time(s)

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Aug 28, 2009 6:54 am Post subject: Dan's Jabiru 3300 Wiring Schematic

At 09:46 PM 8/27/2009, you wrote:

 	  Quote: 	
		  



I have taken a portion of Dan's schematic that pertains to the 

dynamo, regulator, and tachometer and simplified it in an attempt to 

better understand it.  I moved the bridge rectifier outside of the 

regulator.  And I added one more diode in series with the tach so 

that the tach only sees half of the dynamo waveform.  By adding this 

extra diode, I believe that the tach will see the same signal 

whether the alternator relay is pulled in or not, since the tach is 

connected in parallel with the dynamo through two diodes.  The 

dynamo frequency is dependent upon the engine speed since it is 

mounted onto the flywheel.  The output voltage will vary depending 

of the state of the disconnect relay and aircraft load.  However, 

the voltage should not affect the tach unless it drops below the 

minimum (2.5 to 5 volts) required.

    Bob, what do you think?  Will Dan's tach work as connected in 

 his schematic if a diode is added in series with it?  Or do I have 

 it all wrong?  And that could be, because I do not know what is 

 inside of the regulator case.


	


   Good question. You know what you do not know.

   Similarly, I know that I know nothing about

   the functional requirements for any particular

   tachometer. It's unwise for me to suggest that

   modification of the tachometer's signal path (by

   breaking one AC lead from the alternator) will

   not have a deleterious  effect on its performance.



   You're on the right track for the crafting an

   experiment and verifying the significance of

   results before you fly the airplane. But the

   "2.5 to 5.0 volts minimum" requirement does

   not speak to distortions of waveform.



   I'm in CA right now sorting out the simple-ideas

   for the outcome of an experiment that was not conducted

   to a useful and significant conclusion before

   flight.



   The short answer to your question is hook it

   up, give it a try. It wouldn't hurt to take some

   'scope waveform data on the relay-open and

   relay-closed conditions. Then share those pictures

   with the the folks who built the tach. It's

   a sure bet that they did not anticipate a need

   to remain functional with one of the AC power

   leads from the dynamo disconnected from the

   rectifier/regulator.

        Bob . . .



         ---------------------------------------

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

user9253

Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan

Posted: Fri Aug 28, 2009 8:59 am Post subject: Re: Dan's Jabiru 3300 Wiring Schematic

Thanks for the reply Bob.  Unfortunately I live a long way from Dan.  Perhaps he will let us know how he connected his tachometer to make it work to his satisfaction.

Joe

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

_________________
Joe Gores

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours Goto page Previous 1, 2
Page 2 of 2

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum