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More MGL Enigma issues

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rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Sat Jun 28, 2014 5:21 pm Post subject: More MGL Enigma issues

To avoid brownout during start up we installed a Mitchell oil pressure gauge as a supplement to the MGL. The tech folks at Mitchell helped us get the right gauge for the VDO single wire pressure sender (VDO p/n 360-004) and everything seemed to be working fine until they weren't. We traced the problem to a failed sender and installed a new one today. Per VDO the sender was installed dry to ensure it has a good ground. It seems to work fine with the Mitchell gauge, but won't produce a steady reading on the MGL. I've tried every setting in the setup menu for the oil pressure sender and the only one that works is for a 0 to 5 volt sender (the other three options are for automotive resistance style, Rotax 5 to 20 mA, and .5 to 4.5 volt). All the others lock up at somewhere between 133 and 139 PSI. With the menu set for the 0 to 5 volt sender the pressure varies between 62 and 80 PSI at 2200 RPM. When I go into the menu that allows me to see the raw data coming into the RADC unit it shows the sender is putting out .32 to .39 volts at 2200 RPM. If I decrease the RPM to 1850 the sender output goes up to .35 to .41 volts. This corresponds to 65 to 85 PSI on the Enigma. The part that truly makes my head hurt is that at VDO's website;

http://www.vdo-instruments.com/sensors/pressure-sensors-switches/pressure-sender-150-psi-1-8-27npt-29-12.html

 The sender is described as sending a signal from 10 to 180 ohms yet, as I said, using the automotive resistance style setting in the setup menu causes the Enigma reading to lock up at 133 PSI.

Last, does anyone know where to get current documentation on the Enigma? What the owner has appears to be an early revision that bears little resemblance to the current software version installed in the EFIS. On MGL's website I get a 404, page not found error when I try the documentation page.

 



Rick Girard



It isn't necessary to have relatives in Kansas City in order to be unhappy.



   - Groucho Marx

 



  [quote][b]

_________________
The smallest miracle right in front of you is enough to make you happy....

user9253

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

Posted: Sun Jun 29, 2014 4:49 am Post subject: Re: More MGL Enigma issues

The VDO 360-004 is a resistance type sender.  It can NOT output a voltage.  The voltage is coming from the Mitchell oil pressure gauge.  Ideally the MGL and Mitchell gauge should each have its own sensor.  But that might not be practical.  It seems that some type of buffer is needed to convert the voltage from the Mitchell to a signal that the MGL can use.

_________________
Joe Gores

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Sun Jun 29, 2014 10:31 am Post subject: More MGL Enigma issues

Joe, all, we tried every possible combination of sensor hook up to the Mitchell and MGL, both together and each alone. Even when the MGL was the only thing hooked up to the sensor the output on the raw data showed the pressure sender between .31 and .41 volts. In the end we left the MGL disconnected and are only driving the Mitchell gauge so the owner can fly while we attempt to figure it out.

Thanks,

Rick

 

On Sun, Jun 29, 2014 at 7:49 AM, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:

 	  Quote: 	
		   --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

 

 The VDO 360-004 is a resistance type sender.  It can NOT output a voltage.  The voltage is coming from the Mitchell oil pressure gauge.  Ideally the MGL and Mitchell gauge should each have its own sensor.  But that might not be practical.  It seems that some type of buffer is needed to convert the voltage from the Mitchell to a signal that the MGL can use.

  

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=425709#425709

 

 

 

 

 

 

 

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-- 

Zulu Delta

Mk IIIC

Thanks, Homer GBYM

It isn't necessary to have relatives in Kansas City in order to be unhappy.

   - Groucho Marx

 

  [quote][b]

_________________
The smallest miracle right in front of you is enough to make you happy....

user9253

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

Posted: Sun Jun 29, 2014 11:34 am Post subject: Re: More MGL Enigma issues

Have you measured the voltage at the instrument-panel end of the sender wires with nothing connected at all?  Or measure the voltage between the sender case and instrument panel ground?  This measurement should be taken with everything electrical turned on.  Maybe there is a poor ground connection someplace.

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jun 29, 2014 1:37 pm Post subject: More MGL Enigma issues

At 01:30 PM 6/29/2014, you wrote:

 	  Quote: 	
		  Joe, all, we tried every possible combination of sensor hook up to 

the Mitchell and MGL, both together and each alone. Even when the 

MGL was the only thing hooked up to the sensor the output on the raw 

data showed the pressure sender between .31 and .41 volts.

In the end we left the MGL disconnected and are only driving the 

Mitchell gauge so the owner can fly while we attempt to figure it out.


	


   Are you using the same 'sender' for both the

   steam gage AND trying to read it with the

   EIS?



   Bob . . .

pestar

Joined: 11 Apr 2007
Posts: 61
Location: Auckland, New Zealand

Posted: Sun Jun 29, 2014 1:42 pm Post subject: Re: More MGL Enigma issues

Join http://www.mglavionicsusers.org/forum/index.php and ask your questions there.  You will get lots of support.



Cheers Peter

_________________
Peter Armstrong
Auckland, New Zealand
DynAero MCR-4S (Do not shoot me Smile

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jun 29, 2014 1:45 pm Post subject: More MGL Enigma issues

At 07:49 AM 6/29/2014, you wrote:

 	  Quote: 	
		  



The VDO 360-004 is a resistance type sender.  It can NOT output a 

voltage.  The voltage is coming from the Mitchell oil pressure 

gauge.  Ideally the MGL and Mitchell gauge should each have its own 

sensor.  But that might not be practical.  It seems that some type 

of buffer is needed to convert the voltage from the Mitchell to a 

signal that the MGL can use.


	


   Opps . . . perhaps this is the answer to my

   recent question. Joe is right, a variable

   resistance transducer must be powered up from

   the companion instrument . . . I presume the

   Mitchell gage has power, ground and transducer

   connectors.



   Once biased up by the Mitchell gage internals,

   there WILL be a variable voltage across the

   transducer terminals that represents the

   MITCHELL gage expectations . . . but since

   the EIS is not privy to exactly what that

   excitation is, it cannot properly interpret

   the voltage.



   If you want BOTH instruments then you'll

   need to set up the EIS to work with a 3-wire,

   linear voltage transducer . . . then add

   an instrument set up to read THAT same

   voltage.



   It's not hard to do if you are handy with

   a soldering iron and a few chips.



   Bob . . .

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Mon Jun 30, 2014 6:26 pm Post subject: More MGL Enigma issues

Thanks Peter.



Rick Girard

do not archive



On Sun, Jun 29, 2014 at 4:42 PM, pestar <peter(at)reivernet.com (peter(at)reivernet.com)> wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "pestar" <peter(at)reivernet.com (peter(at)reivernet.com)>

  

 Join http://www.mglavionicsusers.org/forum/index.php and ask your questions there.  You will get lots of support.

 

 Cheers Peter

 

 Peter Armstrong

 Auckland, New Zealand

 

 --------

 Peter Armstrong

 Auckland, New Zealand

 DynAero MCR-4S (Do not shoot me  ).

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=425741#425741

 

 

 

 

 

 

 

 ===========

  -

 ric-List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

 ===========

 MS -

 k">http://forums.matronics.com

 ===========

 e -

           -Matt Dralle, List Admin.

 t="_blank">http://www.matronics.com/contribution

 ===========

 

 

 

 	




-- 

Zulu Delta

Mk IIIC

Thanks, Homer GBYM

It isn't necessary to have relatives in Kansas City in order to be unhappy.

   - Groucho Marx

 

  [quote][b]

_________________
The smallest miracle right in front of you is enough to make you happy....

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Tue Jul 01, 2014 8:10 am Post subject: More MGL Enigma issues

The MGL was the ONLY thing connected to the sender and the data still said that the sender was reading .31 to .41 volts. Any voltage would have been supplied by the MGL's RADC box. The output to the Enigma EFIS is through a proprietary cable, only the input cables from the various senders are user supplied. Going into the RADC to attempt adaptation or a fix is above my pay grade. :-} 



Rick Girard



On Sun, Jun 29, 2014 at 4:45 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>

  



 At 07:49 AM 6/29/2014, you wrote:

  	  Quote: 	
		   --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

 

 The VDO 360-004 is a resistance type sender.  It can NOT output a voltage.  The voltage is coming from the Mitchell oil pressure gauge.  Ideally the MGL and Mitchell gauge should each have its own sensor.  But that might not be practical.  It seems that some type of buffer is needed to convert the voltage from the Mitchell to a signal that the MGL can use.

  	
 

   Opps . . . perhaps this is the answer to my

   recent question. Joe is right, a variable

   resistance transducer must be powered up from

   the companion instrument . . . I presume the

   Mitchell gage has power, ground and transducer

   connectors.

 

   Once biased up by the Mitchell gage internals,

   there WILL be a variable voltage across the

   transducer terminals that represents the

   MITCHELL gage expectations . . . but since

   the EIS is not privy to exactly what that

   excitation is, it cannot properly interpret

   the voltage.

 

   If you want BOTH instruments then you'll

   need to set up the EIS to work with a 3-wire,

   linear voltage transducer . . . then add

   an instrument set up to read THAT same

   voltage.

 

   It's not hard to do if you are handy with

   a soldering iron and a few chips.

 

 

 

   Bob . . . 

 

 ====================================

  -

 ric-List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

 ====================================

 MS -

 k">http://forums.matronics.com

 ====================================

 e -

           -Matt Dralle, List Admin.

 t="_blank">http://www.matronics.com/contribution

 ====================================

 

 

 

 



	




-- 

Zulu Delta

Mk IIIC

Thanks, Homer GBYM

It isn't necessary to have relatives in Kansas City in order to be unhappy.

   - Groucho Marx

 

  [quote][b]

_________________
The smallest miracle right in front of you is enough to make you happy....

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Tue Jul 01, 2014 8:14 am Post subject: More MGL Enigma issues

Missed a thought. So, if I understand this, the gauge and RADC send a voltage through the VDO sender that varies its resistance with pressure and changes the voltage. This voltage change is then either converted to a meter reading or a digital output that goes to the EFIS. Yesno? 



Rick



On Tue, Jul 1, 2014 at 11:09 AM, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:

  	  Quote: 	
		  The MGL was the ONLY thing connected to the sender and the data still said that the sender was reading .31 to .41 volts. Any voltage would have been supplied by the MGL's RADC box. The output to the Enigma EFIS is through a proprietary cable, only the input cables from the various senders are user supplied. Going into the RADC to attempt adaptation or a fix is above my pay grade. :-}  



Rick Girard



On Sun, Jun 29, 2014 at 4:45 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

   	  Quote: 	
		  --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>

   



 At 07:49 AM 6/29/2014, you wrote:

  	  Quote: 	
		   --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

 

 The VDO 360-004 is a resistance type sender.  It can NOT output a voltage.  The voltage is coming from the Mitchell oil pressure gauge.  Ideally the MGL and Mitchell gauge should each have its own sensor.  But that might not be practical.  It seems that some type of buffer is needed to convert the voltage from the Mitchell to a signal that the MGL can use.

   	
 

   Opps . . . perhaps this is the answer to my

   recent question. Joe is right, a variable

   resistance transducer must be powered up from

   the companion instrument . . . I presume the

   Mitchell gage has power, ground and transducer

   connectors.

 

   Once biased up by the Mitchell gage internals,

   there WILL be a variable voltage across the

   transducer terminals that represents the

   MITCHELL gage expectations . . . but since

   the EIS is not privy to exactly what that

   excitation is, it cannot properly interpret

   the voltage.

 

   If you want BOTH instruments then you'll

   need to set up the EIS to work with a 3-wire,

   linear voltage transducer . . . then add

   an instrument set up to read THAT same

   voltage.

 

   It's not hard to do if you are handy with

   a soldering iron and a few chips.

 

 

 

   Bob . . . 

 

 ====================================

  -

 ric-List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

 ====================================

 MS -

 k">http://forums.matronics.com

 ====================================

 e -

           -Matt Dralle, List Admin.

 t="_blank">http://www.matronics.com/contribution

 ====================================

 

 

 

 



	




-- 

Zulu Delta

Mk IIIC

Thanks, Homer GBYM

It isn't necessary to have relatives in Kansas City in order to be unhappy.

    - Groucho Marx

 

 	




-- 

Zulu Delta

Mk IIIC

Thanks, Homer GBYM

It isn't necessary to have relatives in Kansas City in order to be unhappy.

   - Groucho Marx

 

  [quote][b]

_________________
The smallest miracle right in front of you is enough to make you happy....

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jul 01, 2014 12:53 pm Post subject: More MGL Enigma issues

At 11:13 AM 7/1/2014, you wrote:

  	  Quote: 	
		  Missed a thought. So, if I understand this, the gauge and RADC send a voltage through the VDO sender that varies its resistance with pressure and changes the voltage. This voltage change is then either converted to a meter reading or a digital output that goes to the EFIS. Yesno?



 Rick 	


    Yes . . . but EACH readout EXPECTS to see

    a voltage/pressure signature that is consistent

    with the BIAS current supplied by that readout.



    The bias currents from TWO readouts will add

    together and produce voltage/pressure values

    that makes sense to neither instrument.



    Theoretically, you might get away with installing

    the VDO/Mitchell sensor/gage combination. Then

    set up the 'smart' display look at the voltage

    and then program the display to accommodate the SAME

    voltage/pressure curve that operates the Mitchell

    gage.



 



 

   Bob . . .    [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jul 01, 2014 2:02 pm Post subject: More MGL Enigma issues

At 11:09 AM 7/1/2014, you wrote:

  	  Quote: 	
		  The MGL was the ONLY thing connected to the sender and the data still said that the sender was reading .31 to .41 volts. Any voltage would have been supplied by the MGL's RADC box. The output to the Enigma EFIS is through a proprietary cable, only the input cables from the various senders are user supplied. Going into the RADC to attempt adaptation or a fix is above my pay grade. :-} 	


   Under what conditions were these two voltages being measured?



   The variable resistance pressure transducer is rated to present

   a terminal to ground value of 10-184 ohms. 



   Here's a thread describing a builder's efforts to adapt

   a VDO 10-180 ohm transducer to an MGL instrumentation

   package.



  http://tinyurl.com/pavxyb4



 [img]cid:.0[/img]



    Data acquired by the builder shows that sender resistance

    is 10 ohms at zero pressure and builds to 180 ohms

    a rated pressure of 10 Bar or 150 PSI. It also

    paints a rather linear transfer function.



    Here's a pdf that describes one builder's approach

    to converting the variable resistance VDO transucer

    into a variable voltage.



  http://tinyurl.com/oc54e9e



    A 300 ohm resistor in series with the gage to a 5-volt

    supply will produce  5 x 10/(300+10) = 160 mV at

    zero pressure and 5 x 100/(300+100) = 1.25 V at

    75 PSI.



    In your case, you're wanting the Mitchell gage to

    take the place of the 300 ohm resistor.  The MGL

    display of .31 to .41 volts as the ONLY excitation

    to the sensor suggests a bias current on the order

    of (0.36/10) = 0.036A or 36 milliamps. If this is

    a constant current, then the voltage would rise to

    (100 x 0.036) = 3.6 volts at 75 PSI. But these are

    things you would need to tell the MGL system to

    read the VDO sensor.



    Hook up the Mitchell gage as the bias source and

    read the zero-pressure voltage value at the transducer. Then

    put shop air to the transducer at about 75 PSI and

    get a new voltage.



    From these two values, you can advise the MGL system

    as to offset and scale factors are for converting

    Mitchell-volts to MGL display in response to VOLTAGE;

    NOT as an interpreter of VDO sensor output.



 

   Bob . . .

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