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  #1  
Old 05-19-2022, 05:50 PM
Desert Rat Desert Rat is offline
 
Join Date: Aug 2018
Location: Wichita KS
Posts: 899
Default how did you guys wire pitot heat annunc. into the G3X?

I have the heated but non-regulated version of garmin's pitot heater and would like to have a CAS "pitot heat on" message.

The original plan was to run a wire off the downstream side of the switch, through a fuseable link and into a discreet input on the GAD27.

Some sort of wire protection is highly desirable if I go this route, because the other wire coming off that terminal is the wire to the heater that's running through a honking big 20 amp breaker.

Unfortunately, I don't think I can get bigger that a 22 wire into the D-sub pin in the GAD27 connector, which would require a ridiculously small 26awg wire to make a fuse link. I don't have any wire that small, and don't know that I could crimp it successfully even if I did.

I considered an inline fuse, but space is extremely limited behind the switch panel, with only about an inch back there, so I can't have anything very bulky.

Is the answer here to make the fuse link 24awg into a 20 awg wire that has some strands cut out to get it to fit in the pin? Or is there a better solution? What did you guys do?
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  #2  
Old 05-19-2022, 10:06 PM
TASEsq TASEsq is offline
 
Join Date: Aug 2017
Location: Melbourne, Australia
Posts: 437
Default

I am working on my planning and doing a wiring diagram and decided to use a relay to run the pitot heat - since my CB's will be above the tunnel under the panel, saved me running heavy wires up to the panel. This way i can use a switch which when on provides a ground to activate the relay. I can use a DPST and also ground a discrete wire which i will run to the GAD27 or GEA24.

Obviously this only shows if the switch is on, not if the probe has any power but better than nothing.
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  #3  
Old 05-20-2022, 08:43 AM
Breezy Breezy is offline
 
Join Date: Nov 2011
Location: Okeana, Ohio
Posts: 126
Default

As pointed out an indicator light or discrete is very binary. It's simply on or off, that is all it will tell you. It becomes necessary to think in terms of cause and effect.
A pitot probe is a high draw component. In todays digital and LED systems it could easily be the highest AMP draw device in the ships electrical system, setting aside the starter.
As you reach for the pitot heat switch observe alternator AMP load. When turned on there will be a significant rise in load verifying the heat coil is energized.
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  #4  
Old 05-20-2022, 08:56 AM
Bavafa Bavafa is offline
 
Join Date: Oct 2007
Location: Sacramento, CA
Posts: 3,910
Default

My setup is exactly like Trent, only my switch provides a 12v to the relay. I simply used one of active high discrete of my GAD27 to the power side of the pitot switch. When the switch is turned on, I get an indication on the G3X for the Pitot being on.
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Last edited by Bavafa : 05-20-2022 at 09:03 AM.
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  #5  
Old 05-20-2022, 09:52 AM
Xavier L Xavier L is offline
 
Join Date: Feb 2017
Location: Jouy-en-Josas, France
Posts: 4
Default

I connected a 1kOhm 1/4W resistor close to the high-power wire, then ran a 22 AWG wire to the GAD27 input.
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  #6  
Old 05-20-2022, 10:31 AM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
Posts: 3,009
Default Regulated

I am using the garmin regulated pitot; it gets turned on during the after start checklist and off during the shutdown checklist. The G3X has built in logic for the heater and you can select from one of three modes. Works great.

I started with the unregulated and then switched. Glad I did.
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  #7  
Old 05-21-2022, 08:28 AM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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Default

Quote:
Originally Posted by Xavier L View Post
I connected a 1kOhm 1/4W resistor close to the high-power wire, then ran a 22 AWG wire to the GAD27 input.
+1

In addition to dropping the current downstream of the resistor, it will also act as a fusible link. a 1/4 watt resistor cannot pass a lot of current before it's internals vaporize and open the circuit.

Larry
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  #8  
Old 05-21-2022, 11:07 AM
Desert Rat Desert Rat is offline
 
Join Date: Aug 2018
Location: Wichita KS
Posts: 899
Default

Quote:
Originally Posted by lr172 View Post
+1

In addition to dropping the current downstream of the resistor, it will also act as a fusible link. a 1/4 watt resistor cannot pass a lot of current before it's internals vaporize and open the circuit.

Larry
But don't you have to solder them in? I'm not crazy about solder joints in something like this.
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  #9  
Old 05-21-2022, 01:06 PM
Xavier L Xavier L is offline
 
Join Date: Feb 2017
Location: Jouy-en-Josas, France
Posts: 4
Default

To solder the resistor, I followed the recommendations given on Page 29 of https://www.verticalpower.com/media/...ual_rev-g1.pdf

If the AWG 22 wire to the GAD27 input is shorted to the ground, the current going through the resistor is approximately 14 V / 1,000 Ohm = 14 mA. The power dissipated by the resistor is then only 14 V * 14 mA = 196 mW, which is OK for a 1/4 W resistor. The GAD27 will think that pitot heat is off until the short is corrected.
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