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trigo(at)mail.telepac.pt
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 Posted: Wed Jan 20, 2016 11:05 am Post subject: On-the-ground power jack |
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Hello group
Figure Z-31A of the Connection, which refers to the wiring of a "Military style Ground Power jack", indicates a 22AWG wire connecting the 2nd coil post of the contactor (where the BLK wire of the OVM-14 is also connected), with the "Main Ground Buss", through a 2A circuit breaker.
Now forgive my dumb question: what is this wire for?
And 2 practical questions:
- can I strike this wire from my system?
- if not, and since the Ground Buss is in the firewall and the Ground power receptacle and contactor are both in the tail of the RV-10, can I simply connect this wire to the negative terminal of the battery?
Regards
Carlos
Enviado do meu iPhone
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nuckolls.bob(at)aeroelect
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| Posted: Wed Jan 20, 2016 11:43 am Post subject: On-the-ground power jack |
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At 01:01 PM 1/20/2016, you wrote:
| Quote: | --> AeroElectric-List message posted by: Carlos Trigo <trigo(at)mail.telepac.pt>
Hello group
Figure Z-31A of the Connection, which refers to the wiring of a "Military style Ground Power jack", indicates a 22AWG wire connecting the 2nd coil post of the contactor (where the BLK wire of the OVM-14 is also connected), with the "Main Ground Buss", through a 2A circuit breaker. |
[img]cid:.0[/img]
The small, third terminal on the "mil-spec"
ground power jack serves a several purposes.
First, the pin is small . . . no high current . . .
just a sample of the voltage available from
the ground power source. Second, the pin is
SHORTER which means that nothing happens on this
pin until the larger two pins are in good
electrical contact wthe sockets in the ground
power plug. Using this pin as a source of
voltage to energize the ground power contactor
prevents the larger pins from trying to CARRY
current during the make/break operations.
The diode in series with that sense lead
prevents the contactor from closing should
you be inadvertently connected to a battery
cart that has been miss-wired and reverse
polarity. the crowbar ov module across the
coil will trigger if your ground power jocky
has inadvertently place the GPU in the 28V
mode . . . it's happened to me twice.
The crowbar ov module is designed to work
against a circuit breaker. In this case, I
suggest a switch-breaker not unlike . . .
[img]cid:.1[/img]
I'm generally not a big fan of breaker-switches.
But in this case, the device can serve two
purposes . . . (1) as breaker to work in concert
with the crowbar ovm and (2) a switch
you can have on the panel that gives YOU
control over the application/removal of
ground power to your airplane.
| Quote: | And 2 practical questions:
- can I strike this wire from my system? |
Not recommended . . .
| Quote: | | - if not, and since the Ground Buss is in the firewall and the Ground power receptacle and contactor are both in the tail of the RV-10, can I simply connect this wire to the negative terminal of the battery? |
That breaker switch should be on your
panel . . . or perhaps on a bracket under
it . . . hence the the LONG wire is from
ground power contactor and the switch-breaker.
The wire between ground bus and the switch-
breaker is short.
Bob . . .
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trigo(at)mail.telepac.pt
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| Posted: Wed Jan 20, 2016 12:36 pm Post subject: On-the-ground power jack |
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Thanks Bob
For the quick response, and the excellent "instructions manual" that came along with the response.
A last question, derived from your explanations:
- When the ground-power jockey connects the female military jack of the battery cart to the airplane, the electrons will not flow unless that breaker-switch you recommended is On, right?
Carlos
Enviado do meu iPhone
No dia 20/01/2016, às 19:34, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> escreveu:
| Quote: | At 01:01 PM 1/20/2016, you wrote:
| Quote: | --> AeroElectric-List message posted by: Carlos Trigo <trigo(at)mail.telepac.pt (trigo(at)mail.telepac.pt)>
Hello group
Figure Z-31A of the Connection, which refers to the wiring of a "Military style Ground Power jack", indicates a 22AWG wire connecting the 2nd coil post of the contactor (where the BLK wire of the OVM-14 is also connected), with the "Main Ground Buss", through a 2A circuit breaker. |
<2547f72d.jpg>
The small, third terminal on the "mil-spec"
ground power jack serves a several purposes.
First, the pin is small . . . no high current . . .
just a sample of the voltage available from
the ground power source. Second, the pin is
SHORTER which means that nothing happens on this
pin until the larger two pins are in good
electrical contact wthe sockets in the ground
power plug. Using this pin as a source of
voltage to energize the ground power contactor
prevents the larger pins from trying to CARRY
current during the make/break operations.
The diode in series with that sense lead
prevents the contactor from closing should
you be inadvertently connected to a battery
cart that has been miss-wired and reverse
polarity. the crowbar ov module across the
coil will trigger if your ground power jocky
has inadvertently place the GPU in the 28V
mode . . . it's happened to me twice.
The crowbar ov module is designed to work
against a circuit breaker. In this case, I
suggest a switch-breaker not unlike . . .
<2547f78b.jpg>
I'm generally not a big fan of breaker-switches.
But in this case, the device can serve two
purposes . . . (1) as breaker to work in concert
with the crowbar ovm and (2) a switch
you can have on the panel that gives YOU
control over the application/removal of
ground power to your airplane.
| Quote: | And 2 practical questions:
- can I strike this wire from my system? |
Not recommended . . .
| Quote: | | - if not, and since the Ground Buss is in the firewall and the Ground power receptacle and contactor are both in the tail of the RV-10, can I simply connect this wire to the negative terminal of the battery? |
That breaker switch should be on your
panel . . . or perhaps on a bracket under
it . . . hence the the LONG wire is from
ground power contactor and the switch-breaker.
The wire between ground bus and the switch-
breaker is short.
Bob . . .
|
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nuckolls.bob(at)aeroelect
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| Posted: Wed Jan 20, 2016 1:11 pm Post subject: On-the-ground power jack |
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At 02:30 PM 1/20/2016, you wrote:
| Quote: | Thanks Bob
For the quick response, and the excellent "instructions manual" that came along with the response.
A last question, derived from your explanations:
- When the ground-power jockey connects the female military jack of the battery cart to the airplane, the electrons will not flow unless that breaker-switch you recommended is On, right? |
Absolutely. If you have the option, the ground
power switch can be included in the DC POWER
group of system switches on your panel. When
ground power is plugged in, you can have
control of it from the pilot's position. Doesn't
need to be ON until you're ready, you can turn
it OFF as you decide.
Some of my readers have added a lamp from the
high side of contactor coil to ground. This
light will indicate when and if ground power is
available.
Bob . . .
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prestonkavanagh
Joined: 27 Nov 2018
Posts: 16
Location: Tarpon Springs
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| Posted: Fri Oct 09, 2020 5:15 pm Post subject: Re: On-the-ground power jack |
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I'm picking up this old thread because of the excellent walk through of the "why" of the circuit....Building a Z101 Cozy and adding a ground power function using Piper jacks. I need to find a suitable overvoltage protector. I don't see the OVM-14 on the B&C site, but I wonder if I can use a Lambda LMOV unit. Or am I better off mucking around with some MOS-FET's? Here's the Lambda OV protection I have in mind - comments?
https://www.ebay.com/itm/Lambda-LMOV-2-Overvoltage-Protector-6-20v-dc/292566713401
The rest of the circuit would not change. Thanks for the help. Preston K.
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PBK3
PA-12, BD-4, RV6a, gliders, Rutan canards |
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user9253
Joined: 28 Mar 2008
Posts: 1920
Location: Riley TWP Michigan
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| Posted: Fri Oct 09, 2020 5:59 pm Post subject: Re: On-the-ground power jack |
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According to this pdf: https://www.mavin.com/pdf/LMOV-9.pdf
The LMOV-2 shorts out the power supply in case of over voltage. So it should work.
Another option is Perihelion Design's over voltage protection module $88.
http://www.periheliondesign.com/lovm.htm
It works by opening a circuit instead of shorting it out.
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Joe Gores |
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ceengland7(at)gmail.com
Guest
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| Posted: Fri Oct 09, 2020 6:23 pm Post subject: On-the-ground power jack |
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On 10/9/2020 8:59 PM, user9253 wrote:
| Quote: |
According to this pdf: https://www.mavin.com/pdf/LMOV-9.pdf
The LMOV-2 shorts out the power supply in case of over voltage. So it should work.
Another option is Perihelion Design's over voltage protection module $88.
http://www.periheliondesign.com/lovm.htm
It works by opening a circuit instead of shorting it out.
--------
Joe Gores
Or the one I linked earlier, from Tomtop.
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