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G3X general purpose inputs

TShort

Well Known Member
I am using several of the general purpose inputs on the G3X for various notifications.
I have used all of the discrete inputs.

I connected both aux fuel pumps (for the extended range tanks) to GP3 and GP4, configured as active hi since they are not controlled through a VPX switch. Based on other threads and discussion with G3X support, I added a resistor and connected the resistor to the ground for each GP pin. These inputs work fine, and generate the desired alert when the pump is switched on. My understanding is that these are "pull down" resistors.

I have an issue with the alert for the main (backup electric) fuel pump. It is controlled by the VPX, so I am configuring it as active low. I understand I need a pull up resistor for this application. I connected this to GP5, with the input to pin 31 and the resistor to pin 30 (POS 5 HI/+5V). For some reason, this doesn't work - the alert stays active all the time.

Do I need to run the pullup resistor to a different pin? The examples in the install manual show pin 50 (Figure 30-2.2), which looks like 12V instead of 5V.

If I need to use pin 50, can I have multiple active low inputs connected to the same pullup resistor?

For some reason this pull up / pull down / active hi/low stuff is the one thing in the install manual that has given me fits.

Thanks in advance for the help.
 
I am using several of the general purpose inputs on the G3X for various notifications.
I have used all of the discrete inputs.

I connected both aux fuel pumps (for the extended range tanks) to GP3 and GP4, configured as active hi since they are not controlled through a VPX switch. Based on other threads and discussion with G3X support, I added a resistor and connected the resistor to the ground for each GP pin. These inputs work fine, and generate the desired alert when the pump is switched on. My understanding is that these are "pull down" resistors.

I have an issue with the alert for the main (backup electric) fuel pump. It is controlled by the VPX, so I am configuring it as active low. I understand I need a pull up resistor for this application. I connected this to GP5, with the input to pin 31 and the resistor to pin 30 (POS 5 HI/+5V). For some reason, this doesn't work - the alert stays active all the time.

Do I need to run the pullup resistor to a different pin? The examples in the install manual show pin 50 (Figure 30-2.2), which looks like 12V instead of 5V.

If I need to use pin 50, can I have multiple active low inputs connected to the same pullup resistor?

For some reason this pull up / pull down / active hi/low stuff is the one thing in the install manual that has given me fits.

Thanks in advance for the help.

Hello Thomas,

To begin with, you might want to make sure you are using the latest (Rev. AE) G3X installation manual.

As shown on page 30-5, it does indeed sound like you have done the right thing to use GP5, pin 31 as an active low input, but we question whether or not this is really an active low signal.

You say this pump is controlled by the VPX. Does the VPX apply power to turn it on (active high), or apply ground to turn it on (active low)?

Thanks,
Steve
 
The VPX switches are just to ground, no power, so it is active low.

I have the most recent revision (AE).

Thanks for the quick reply!
 
I should clarify the above.

For this pump, I am generating an alert (reminder) that the boost pump switch is on, not monitoring power to the pump itself (as I can do that with the VPX).

The VPX switch is just a ground, no power, hence this one is active low instead of active high like the two fuel pumps mentioned above.

Thanks
 
I should clarify the above.

For this pump, I am generating an alert (reminder) that the boost pump switch is on, not monitoring power to the pump itself (as I can do that with the VPX).

The VPX switch is just a ground, no power, hence this one is active low instead of active high like the two fuel pumps mentioned above.

Thanks

Hello Thomas,

We can do a better job of helping you if you email [email protected]. We can ask for screen shots of your configuration, wiring sketch, etc.

For the GEA 24 discrete input to register as an active low signal, the voltage on that pin needs to be <3.5Vdc, and we suspect this is not happening when you activate the pump.

Thanks,
Steve
 
Last edited:
So the answer for those following along at home....

If you want to create an active low alert for one of the VPX switches (which just connect to ground), you need to either:

- use a DPST switch, and isolate the discrete or GP input from the VPX input

or

- use a diode to isolate the switch inputs from each other.

I chose option #1, since I had a switch laying around and I didn't want to cut into my wiring that was already in place for the VPX.

If you choose option #2, the diode is a 1N4005; thanks to Larry Bowen for giving me feedback on the process. He had success isolating both inputs with individual diodes.

Thanks to the G3X guys for the great support!
 
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