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Combining VP-X Switch Grounds

grayforge

grayforge

Well Known Member
Just wondering what most VP-X owners are doing and what Vertical Power recommends on grouping the switch grounds together.

I can see pros and cons for both grouping grounds and keeping separate grounds.

Running individual grounds to the Forest of Tabs:
  1. Lots of points of failure, but any single failure only takes out one device.
  2. Adds a bit of weight

Grouping grounds together and running one wire to the Forest of Tabs:
  1. Fewer points of failure, but a failure could take out many or all devices.
  2. A little less weight

If one were to group the grounds together, I could see a couple ways to do it:
a. Wire each switch's ground to the next, placing 2 wires in each terminal and the last terminal goes to the Forest of Tabs.
b. Add a terminal block of some sort. One line gets grounded to the FoTs and the other terminals go to each switch. (probably not the ideal method since it doesn't buy you much)

Thoughts?

Thanks!
Russ
 
What I did was tie all the switch grounds together and added multiple connections of this bus to the FOT.

Keep in mind that if you lost all your VP-X switch grounds, you could still turn items off and on from the EFIS...
 
Russ, it appears that you have a good understanding of the options.

For most items, I did run a dedicated ground. But on less critical items, I did run a single ground to a group of items like the switches. Like Brian mentioned, you can still turn things on and off via the efis should the switch fail.

bob
 
Switch grounds----------for what, the internal light???

Virtually all of the switches are on the supply side, not the ground. Only exception I can think of are on the control stick for PTT, AP, and trim, or the master.

Or, is this something unique to the way the VP unit works??
 
What about a single bar of copper

I have seen setups where someone uses a row of switches with screw terminals and then just drills out a copper bar with the right spacing to screw to the terminal of each switch. Then, the copper bar is grounded to a single source. It seems simple and less likely to have a failures.
 
Mike S said:
Switch grounds----------for what, the internal light???

Virtually all of the switches are on the supply side, not the ground. Only exception I can think of are on the control stick for PTT, AP, and trim, or the master.

Or, is this something unique to the way the VP unit works??
Click to expand...

Mike,

The VP-X inputs are active low. Ground the input and it turns on whatever is assigned to it. The switch is switching signal level current only.
 
my VPX switches:
20140502_12154611.jpg
 
I tied all switch grounds to a bus bar and connected it to a thicker wire out to my single ground point on the firewall
 
Mine are all tied together and one wire to the FOT. My thoughts are if by some catastrophe that wire gets broken (bundled well, highly unlikely) my Efis will stay up due to the backup battery...and I'll switch everything from there. If that battery fails, the MFD is always up as long as the Batt Master is on.
 
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A

I crimped 2 wires to each terminal and then the end of the chain to the firewall forest of tabs. Simple and clean, and if it fails you can use the EFIS to control it.
 
Good info!

The copper bus bar is a simple solution, though a little heavier for my needs since, as Brian mentioned, these switches handle very little current. Plus, I'm using all Fast-On tabs.

I like the combo approach: A few direct links for anything really important and the rest can be daisy chained together.

Also an excellent point that the EFIS can be used to switch things on & off with a ground failure... but wouldn't the EFIS be one of the items switched off if it was part of the ground daisy chain?

Thanks!
Russ
 
grayforge said:
Good info!

The copper bus bar is a simple solution, though a little heavier for my needs since, as Brian mentioned, these switches handle very little current. Plus, I'm using all Fast-On tabs.

I like the combo approach: A few direct links for anything really important and the rest can be daisy chained together.

Also an excellent point that the EFIS can be used to switch things on & off with a ground failure... but wouldn't the EFIS be one of the items switched off if it was part of the ground daisy chain?

Thanks!
Russ
Click to expand...

In my case with the VP-X Pro and the G3X, the MFD is always on when the master is on and it is the one that talks to the VP-X. There is no switch to turn it off other than the master.
 
grayforge said:
Good info!

The copper bus bar is a simple solution, though a little heavier for my needs since, as Brian mentioned, these switches handle very little current. Plus, I'm using all Fast-On tabs.

I like the combo approach: A few direct links for anything really important and the rest can be daisy chained together.

Also an excellent point that the EFIS can be used to switch things on & off with a ground failure... but wouldn't the EFIS be one of the items switched off if it was part of the ground daisy chain?

Thanks!
Russ
Click to expand...
My 'bus bar'( image above) is not copper but thinner, lighter brass to match the metal used in the switches.
 
Brian, does your G3X MFD stay on through cranking the engine or do you have a secondary battery to keep it up?

I have a single G3X Touch GDU, so one display for both PFD and MFD.
 
grayforge said:
Brian, does your G3X MFD stay on through cranking the engine or do you have a secondary battery to keep it up?

I have a single G3X Touch GDU, so one display for both PFD and MFD.
Click to expand...

Yes it does and it does have an isolated backup battery on the backup power inputs.

For the VP-X to work properly with the G3X, the configurator requires that the screen that is controlling the VP-X gets connected to a specific pin and that pin is hot all the time after the master comes on and the VP-X boots.
 
Thats What I Did

Steve Ashby said:
I have seen setups where someone uses a row of switches with screw terminals and then just drills out a copper bar with the right spacing to screw to the terminal of each switch. Then, the copper bar is grounded to a single source. It seems simple and less likely to have a failures.
Click to expand...

Picture%2520004.jpg
 
grayforge said:
Good info!

The copper bus bar is a simple solution, though a little heavier for my needs since, as Brian mentioned, these switches handle very little current. Plus, I'm using all Fast-On tabs.

I like the combo approach: A few direct links for anything really important and the rest can be daisy chained together.

Also an excellent point that the EFIS can be used to switch things on & off with a ground failure... but wouldn't the EFIS be one of the items switched off if it was part of the ground daisy chain?

Thanks!
Russ
Click to expand...


Like I mentioned in my previous post, the only grounds I daisy chained were those that went to a bank of switches. Every piece of avionics gear has a dedicated ground. Most EFIS are pretty sensitive about having a good ground, especially where engine sensors are involved.

Btw, there are some devices, such as a Garmin gtn650 that has multiple grounds due to current requirement and having to use 20/22 awg wire with the high density pins.

Remember the ground wire has to be just as fat as the power source, so mixing up dissimilar current draws in a daisy chain requires additional thought and planning. Usually not a good idea.
 
Bob, I agree with everything you said.

The only grounds I'm considering combining are the low current switch grounds for signaling the VP-X which device to power on and off. All devices will have their own dedicated power grounds leading back to the Forest of Tabs.
 
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