KJBSouth
Well Known Member
I've had a VPX-Pro ever since Oshkosh '15. SteinAir is now making harnesses for a Dual G3X Touch panel while I'm preparing to do the power distribution wiring for a single battery dual alternator setup. It has not been easy to wrap my head around the power distribution details. I've made some simplified drawings of the system and hope they are OK and may help others in their planning.
Power Distribution Overview
Not shown in this diagram are voltage regulators, solenoid diodes, specific load devices, etc. Wiring diagrams these are not.
A scenario for understanding the diagram would be:
1. The pilot has just climbed in the A/C with all switches off. Turning on the Master Switch grounds the Battery Contactor coil and the solenoid closes sending power to the VPX. The VPX in turn sends power through the other pole of the Master Switch to the Field coil of the Main Alternator.
2. Battery power also goes to the Endurance Bus through the power diode. Current is limited along that path to the Essential Devices due to the diode voltage drop.
3. The VPX also supplies power to two PMags when the pilot flips the mag switches from off to Start/Run. (The PMags are not shown. See the last drawing below.)
4. The pilot presses the momentary start switch; the starter contactor closes; the prop spins and the engine starts. At this point both alternators are spinning but only the 60 amp main alternator is pushing electrons toward the battery. Depending upon RPM, the PMags may or may not be drawing field coil power from the VPX.
5. The plane takes off and all is fine until the battery contactor, the main alternator, the Master switch, the VPX or connectors between them fail. Then, devices with internal batteries continue to operate and all else goes dark. The pilot turns off the Master Switch, turns on the Endurance Bus Switch/Breaker, turns on the Auxiliary Alternator Switch and continues to an original or revised destination. Devices not on the Endurance Bus or without an internal battery remain dark. Note: The Aux Alternator can be set up to operate along with the Main Alternator. I choose to let it idle as I prefer to know from whence the electrons come.
As noted on the drawing this is my interpretation of Bob Nuckolls Z12 diagram using a VPX as the main power distribution bus. Bob recommends powering a cabin light directly from the battery bus. I hesitate to do that as I would be sure to leave it on and kill the battery some time.
AeroLEDs and Switches
I like lots of light. I want if both for recognition and for landing and taxi. Bring on the LEDs. This summer I installed AeroLED Vx and Pulsar LEDs in the wingtips, and AeroSun LEDs in the leading edges. A SunTail light/strobe will go in the rudder.
With four different lights, each with two or more selectable functions, how should they be wired? I wanted as few toggle switches as possible. The solution was to use two DPDT three position On-Off-On switches. One switch controls the four landing lights. It is up for landing and down for recognition (synchronized Wig/Wag).
The only compromise was to include the Vx taxi lights on the Strobe/Nav light switch. It is up for daytime strobe (and taxi) and down for night Strobe, Taxi and Navigation.
Seat Heaters
I like seat heaters in my cars, so I?m sure they will be appreciated in the RV. Again, three position DPDT On-Off-On switches are used. I read that the seat heaters used in A/C have high and low settings. One of the switch poles sends power to the seats while the other lights a panel LED reminding the pilot that the PAX may be cold. The annunciator is lit when it?s signal lead is grounded.
This diagram shows my planned use of double pole On-Off-On toggles for Master and Magneto Switches. Turning on the Master switch also supplies field power to the Main Alternator.
The PMag switch either supplies power to the mag for operation below ~800RPM, or it grounds the P- lead. In the center Test position during preflight runup it reveals whether the PMag is self-powered, assuming the other PMag is off.
These forums and the aviation community have been a great help to me in planning and building "Dream Weaver" so far. Thanks.
Power Distribution Overview
Not shown in this diagram are voltage regulators, solenoid diodes, specific load devices, etc. Wiring diagrams these are not.
A scenario for understanding the diagram would be:
1. The pilot has just climbed in the A/C with all switches off. Turning on the Master Switch grounds the Battery Contactor coil and the solenoid closes sending power to the VPX. The VPX in turn sends power through the other pole of the Master Switch to the Field coil of the Main Alternator.
2. Battery power also goes to the Endurance Bus through the power diode. Current is limited along that path to the Essential Devices due to the diode voltage drop.
3. The VPX also supplies power to two PMags when the pilot flips the mag switches from off to Start/Run. (The PMags are not shown. See the last drawing below.)
4. The pilot presses the momentary start switch; the starter contactor closes; the prop spins and the engine starts. At this point both alternators are spinning but only the 60 amp main alternator is pushing electrons toward the battery. Depending upon RPM, the PMags may or may not be drawing field coil power from the VPX.
5. The plane takes off and all is fine until the battery contactor, the main alternator, the Master switch, the VPX or connectors between them fail. Then, devices with internal batteries continue to operate and all else goes dark. The pilot turns off the Master Switch, turns on the Endurance Bus Switch/Breaker, turns on the Auxiliary Alternator Switch and continues to an original or revised destination. Devices not on the Endurance Bus or without an internal battery remain dark. Note: The Aux Alternator can be set up to operate along with the Main Alternator. I choose to let it idle as I prefer to know from whence the electrons come.
As noted on the drawing this is my interpretation of Bob Nuckolls Z12 diagram using a VPX as the main power distribution bus. Bob recommends powering a cabin light directly from the battery bus. I hesitate to do that as I would be sure to leave it on and kill the battery some time.
AeroLEDs and Switches
I like lots of light. I want if both for recognition and for landing and taxi. Bring on the LEDs. This summer I installed AeroLED Vx and Pulsar LEDs in the wingtips, and AeroSun LEDs in the leading edges. A SunTail light/strobe will go in the rudder.
With four different lights, each with two or more selectable functions, how should they be wired? I wanted as few toggle switches as possible. The solution was to use two DPDT three position On-Off-On switches. One switch controls the four landing lights. It is up for landing and down for recognition (synchronized Wig/Wag).
The only compromise was to include the Vx taxi lights on the Strobe/Nav light switch. It is up for daytime strobe (and taxi) and down for night Strobe, Taxi and Navigation.
Seat Heaters
I like seat heaters in my cars, so I?m sure they will be appreciated in the RV. Again, three position DPDT On-Off-On switches are used. I read that the seat heaters used in A/C have high and low settings. One of the switch poles sends power to the seats while the other lights a panel LED reminding the pilot that the PAX may be cold. The annunciator is lit when it?s signal lead is grounded.
This diagram shows my planned use of double pole On-Off-On toggles for Master and Magneto Switches. Turning on the Master switch also supplies field power to the Main Alternator.
The PMag switch either supplies power to the mag for operation below ~800RPM, or it grounds the P- lead. In the center Test position during preflight runup it reveals whether the PMag is self-powered, assuming the other PMag is off.
These forums and the aviation community have been a great help to me in planning and building "Dream Weaver" so far. Thanks.
