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G3X Garmin EFIS

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fedico94(at)mchsi.com
Guest

Posted: Thu Jun 14, 2012 2:48 pm Post subject: G3X Garmin EFIS

need advice

I want to test the hall effect sensor wire input to the G3X (Slick Mag sensor from UMA).  I have never gotten the rpm sensor to test as one would a cam shaft hall effect sensor on a car with an analogue voltmeter.    According to Klaus Savier's instructions the input signal from his device will record on the G3X

His signal from the Plasma II puts out a square wave (rather than sine wave) at 10V amplitude and 

0.3me ? width.  2 pulses per revolution so about so for 2k rpm need 4K pulses per min.

Is there a reasonably priced pulse generator that will send out a signal like this or is there place to get it locally like radio shack ?



The flap indicator does not work.  it is dependent upon a slde potentiometer from Ray Allen

Is there a way to build a device to send a signal down the input wire to the G3X that varies voltage ? The G3X displays 0.3 V on the flap panel but no chage as I run the flaps up and down. I assume the max voltage going in is 0.3V.  I thought of using a 9 V battery with a potentiometer and this may be useful for the fuel senders as well. 



I have yet to test the fuel tank senders to see if they work.  Very disappointed that this professionally assembled suite of Garmin equipment has some major problems in receiving a signal.

Hard to tell if it is the senders or the LSU computer brain.  So far the senders all check out as working properly.  My main problem is getting access to data to safely test the input signal wires for the RPM sensor, but Klaus Savier has some information on his Plasma II device for electronic signal to the input of the RPM of the G3X.  Prior to installation I use OHM meter to make sure the supplied harneses had continuity and correct pin readout.  So much for plug-n-play.

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jun 15, 2012 6:41 am Post subject: G3X Garmin EFIS

At 05:45 PM 6/14/2012, you wrote:

 --> AeroElectric-List message posted by: fedico94(at)mchsi.com



 need advice

 I want to test the hall effect sensor wire input to the G3X (Slick Mag sensor from UMA).  I have never gotten the rpm sensor to test as one would a cam shaft hall effect sensor on a car with an analogue voltmeter.



   Sensors that can be 'read' with an analog

   voltmeter are generally variable reluctance

   devices . . . 

         

   



 

   

   These have a permanent magnet center pole piece with

   many turns of 'cat hair' wound around them. When the

   teeth of a ferrous gear fly past the end of the pole

   piece, the change in magnetic flux around the wires

   generates a small, generally sinusoidal, ac waveform

   with a frequency equal to teeth-per-second and an

   amplitude proportional to teeth-per-second.



   On the other hand, a 'hall effect device' for RPM

   sensing generally depends on an external magnetic

   field (like the one that spins around the shaft of

   a magneto). It's usually a 3-wire device (ground,

   signal and power) but CAN be a 2-wire device for

   accommodating instruments. These need to be powered

   up by 3-15 volts DC and the output signal is generally

   a square wave, again frequency equal to pole passages

   per second but an amplitude fixed to some value close

   to the power supply voltage.



 [img]cid:.0[/img]



 

   So if the sensor you're trying to test is indeed a Hall

   Effect device, you'll need to wire it up to emulate the

   power supply and signal loads present in normal operations.

   Observation of a the output signal will require an

   oscilloscope as opposed to a simple voltmeter.



 According to Klaus Savier's instructions the input signal from his device will record on the G3X

 His signal from the Plasma II puts out a square wave (rather than sine wave) at 10V amplitude and 

 0.3me ? width.  2 pulses per revolution so about so for 2k rpm need 4K pulses per min.



 Is there a reasonably priced pulse generator that will send out a signal like this or is there place to get it locally like radio shack ?



    Sure, it's called a 555 timer. 



 



 The flap indicator does not work.  it is dependent upon a slde potentiometer from Ray Allen

 Is there a way to build a device to send a signal down the input wire to the G3X that varies voltage ? The G3X displays 0.3 V on the flap panel but no chage as I run the flaps up and down. I assume the max voltage going in is 0.3V.  I thought of using a 9 V battery with a potentiometer and this may be useful for the fuel senders as well. 



   That seems likely.



 

 I have yet to test the fuel tank senders to see if they work.  Very disappointed that this professionally assembled suite of Garmin equipment has some major problems in receiving a signal.

 Hard to tell if it is the senders or the LSU computer brain.  So far the senders all check out as working properly.  My main problem is getting access to data to safely test the input signal wires for the RPM sensor, but Klaus Savier has some information on his Plasma II device for electronic signal to the input of the RPM of the G3X.  Prior to installation I use OHM meter to make sure the supplied harneses had continuity and correct pin readout.  So much for plug-n-play.



   Garmin is pretty good at displaying the right

   numbers representing various system values. The

   problem is with the wide variety of sensor styles,

   scale factors, offsets and wave shapes. Had Garmin

   supplied all components they would have been married

   in production. But as you've discovered, doing the

   engagement, marriage and honeymoon yourself can

   be challenging. 



 These have a permanent magnet center pole piece with

   many turns of 'cat hair' wound around them. When the

   teeth of a ferrous gear fly past the end of the pole

   piece, the change in magnetic flux around the wires

   generates a small, generally sinusoidal, ac waveform

   with a frequency equal to teeth-per-second and an

   amplitude proportional to teeth-per-second.



   On the other hand, a 'hall effect device' for RPM

   sensing generally depends on an external magnetic

   field (like the one that spins around the shaft of

   a magneto). It's usually a 3-wire device (ground,

   signal and power) but CAN be a 2-wire device for

   accommodating instruments. These need to be powered

   up by 3-15 volts DC and the output signal is generally

   a square wave, again frequency equal to pole passages

   per second but an amplitude fixed to some value close

   to the power supply voltage.



   So if the sensor you're trying to test is indeed a Hall

   Effect device, you'll need to wire it up to emulate the

   power supply and signal loads present in normal operations.

   Observation of a the output signal will require an

   oscilloscope as opposed to a simple voltmeter.



  	  Quote: 	
		  According to Klaus Savier's instructions the input signal from his device will record on the G3X

 His signal from the Plasma II puts out a square wave (rather than sine wave) at 10V amplitude and 

 0.3me ? width.  2 pulses per revolution so about so for 2k rpm need 4K pulses per min.Is there a reasonably priced pulse generator that will send out a signal like this or is there place to get it locally like radio shack ? 	


    Sure, it's called a 555 timer. See schematic 



 [img]cid:.1[/img]



         According to the calculator just below this image at



  http://home.cogeco.ca/~rpaisley4/LM555Astable.GIF



        100 ohms at R1, 3300 ohms at R2, 4.7 uF at

        C1 will give you about 45 Hz, 2700 pulses

        per minute or 1350 rpm equivalent test signal.

        Running this test generator on a 9v battery

        would probably be close enough to the 10v pulse

        generated by the Lightspeed system.



 



 

 The flap indicator does not work.  it is dependent upon a slde potentiometer from Ray Allen

 Is there a way to build a device to send a signal down the input wire to the G3X that varies voltage ? The G3X displays 0.3 V on the flap panel but no chage as I run the flaps up and down. I assume the max voltage going in is 0.3V.  I thought of using a 9 V battery with a potentiometer and this may be useful for the fuel senders as well. 



   That seems likely.



 I have yet to test the fuel tank senders to see if they work.  Very disappointed that this professionally assembled suite of Garmin equipment has some major problems in receiving a signal.

 Hard to tell if it is the senders or the LSU computer brain.  So far the senders all check out as working properly.  My main problem is getting access to data to safely test the input signal wires for the RPM sensor, but Klaus Savier has some information on his Plasma II device for electronic signal to the input of the RPM of the G3X.  Prior to installation I use OHM meter to make sure the supplied harneses had continuity and correct pin readout.  So much for plug-n-play.



   Garmin is pretty good at displaying the right

   numbers representing various system values. The

   problem is with the wide variety of sensor styles,

   scale factors, offsets and wave shapes. Had Garmin

   supplied all components they would have been married

   in production. But as you've discovered, doing the

   engagement, marriage and honeymoon yourself can

   be challenging. 



 

 

   Bob . . .

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fedico94(at)mchsi.com
Guest

Posted: Fri Jun 15, 2012 5:54 pm Post subject: G3X Garmin EFIS

thanks for your timely and accurate advice.  I researched the internet last night and it seems a number of schools use the 555 timer circuits.  Your calculations and drawing will make my my breadboard assembly easy.  Unfortunately I found major wiring snafu in G3X system.  The signal input wire does trace to the appropriate pin 17 of the 80 pin J732 LSU connector.  Unfortunately I get a voltmeter reading of 13.5 out of this wire.  The power should come form pin 58 wire but has no power coming out.  It seems this system is to complex to assemble, even for a large avionics shop in northern US. 

---

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