Xenos Wire Schematic

[sonex1374]

Rick,

Here are a few comments from a quick review.

1) You might want a diode in the cross-feed connection between the soaring battery and the main power bus. This would allow power to flow from the main bus to the avionics bus, but not the other way around. Using the diode would prevent you from drawing down the soaring battery with engine related loads (like the alternator field or the aux jacks/usb).

2) The avionics bus lists 3A for the transponder and 7A for the comm radio. This seems high for the comm.

3) You may want a usb port on the avionics bus (especially if using comment #1).

4) The main power bus key switch shows a 7A fuse. The starter solenoid will likely only draw a couple amps and you could go with a 5A fuse.

5) Switch S1 is depicted as a 2-position switch. One position is Battery Off & Alternator Off, the other is Battery On & Alternator On. Is this what you intended, or did you mean to use a 3-position switch for OFF-BAT-BAT+ALT?

6) On switch S1 there is a jumper from pin 2 to pin 1 that I don't understand what you're showing. There is a similar jumper on the key switch between Bat and S.

7) The Starter is shown with an integral solenoid, but you also show a separate starter solenoid. I suggest deleting the integral solenoid from the starter depiction.

8) I see you're using a traditional wound-field alternator instead of the permanent magnet alternator common on the Jabiru engine. It looks like you're using a battery contactor to control the (40A or 60A?) alternator output. This contactor will consume an amp or two on it's own, and may be overkill for your normal alternator output. You might swap this out for a conventional relay and save the power. I also don't see any way to control the alternator other than the over-voltage module (see comment 5).

9) The mag kill wires don't show shielded wire. You'll want shielded wire to control the radio static coming off those kill wires.

Jeff

[racaldwell]

Jeff, thank you for critiquing my schematic. I appreciate it; the more eyes the better.

Here is my thinking about why I did what I did.

1. I decided (after I bought one) not to use the Schottky diode because of the voltage drop across it. I will use lithium batteries and they need 13.5V (13V minimum) to charge. I have the 40A alternator from CAMit on my CAMit 3300. I don't know it's output voltage from the internal regulator and I don't know if it is adjustable. So I plan to minimize the voltage drop where I can by using the FATWIRE from Pherihelion Deigns (sp?) and not use the diode.

2. The Garmin GTR 200 manual specs a 7.5A CB and 20 AWG wire so I am following their instructions.

3. Not a bad idea. But for now I'll plan to minimize the drain on the soaring battery and not recharge the I-pad while soaring. That is easy to change later.

4. Point taken.

5. I intended it to be this way; either all on or all off. I have it like this in my RV6 and never needed it any different in over 20 yrs of flying it.

6. That is the MOV diode from the Nuckolls schematics. I used his as a starting point and his autocad blocks of the pieces are drawn that way. I don't need them actually because I am using the Gigavac contactors and that is built internally.

7. Yes, you are right.

8. I am using the Gigavac contactor as the master solenoid. It has a two coil design so after it is pulled in, only the holding coil remains active and it uses very little current. I am using another Gigavac contactor to drop out the B-lead for over voltage protection. I am using the Pherihelion Design overvoltage module to control that B-lead contactor. I changed the schematic to have a CB instead of a fuse for the overvoltage module control. That way I can pull the CB if I have to manually kill the alternator.

9. Yes, the mag p-leads need to be shielded. I just didn't draw it correctly.

Again, thanks for your input.

Rick Caldwell
Xenos 0057

[sonex1374]

...[snip] 5. I intended it to be this way; either all on or all off. I have it like this in my RV6 and never needed it any different in over 20 yrs of flying it. ...[snip]... I changed the schematic to have a CB instead of a fuse for the overvoltage module control. That way I can pull the CB if I have to manually kill the alternator.

Rick,

All your decisions deem logical and look good to me. I was concerned that you didn't have a way to manually deactivate your alternator, but it sounds like you're using a pullable circuit breaker for control and that will work fine. You may want to depict that (a pullable CB) on your diagram for clarity.

Best of luck,

Jeff

[Spaceman]

9) The mag kill wires don't show shielded wire. You'll want shielded wire to control the radio static coming off those kill wires.

Jeff

I've seen a lot of wiring diagrams that use shielded wires for the mag grounds, but why? Isn't it an open circuit any time the mags are running? I figured people used shielded wires just for simplicity to use the shield as the path from the switch back to the mag body

[sonex1374]

Chris,

The wire attached to the kill terminal on the mags acts like an antenna and throws a lot of RFI static into your comm radio and instruments. Shielding intercepts this RFI radiation and keeps it out of your electronics.

There is a high-voltage pulse created by the mag that either passes thru the kill wire (if possible) or jumps the spark plug gap and fires the plug. The mag kill wire is constantly attempting to conduct that pulse to ground. When the mag is "dead" or inactivated that wire is connected to ground and the pulse is also sent to ground. However, when the kill switch is open (e.g. not connected to ground) this wire becomes a very efficient radiator of this energy into the radio frequency band and throws lots of static.

The mag itself couldn't care less about shielding this wire, so long as there's a switch and path to ground it's happy. What many people do is to use the shield as the return path for the mag kill wire. This way the shield does double-duty - it acts as an RFI-blocker while the mag is hot, and as a ground return path when the mag is cold. There's nothing preventing you from using a kill wire and separate shielding, but then you need two runs of shielded cable instead of a single run (the first run goes from the mag to the switch, the second from the switch to the ground). Using a single shielded wire, the first part of the path is the center wire from the mag to the switch, and the second part is from the switch back to the mag and a nearby grounding point.

Jeff

[Spaceman]

Ah, that all makes sense. Thanks for the explanation! I don't think any of that is spelled out in the aerovee manual.

[rick9mjn]

here is my 2 cent idea, to us people who need a picture to go along the the text. do a google search for "magneto diagram " , or try this link ""if it works"
good day / rick /
https://electronics.stackexchange.com/q ... ion-system

[rick9mjn]

amother 2 cent idea, here is a good post from the EAA about this subject.......see link ...
/ good day / rick
https://www.eaa.org/eaa/aircraft-buildi ... adio-noise

[racaldwell]

Just a note to anyone in the future who may actually use my schematic:

The 15A fuse I had between the main and avionics bus has been increased to 30A. I found out with a near drained AUX battery and all avionics on and transmitting on the comm, the 15A is too little.

Other than that, the design is working well. What I really like is I can isolate the GRT Sport EX on the AUX battery when the main battery starts the engine so I have all engine data instantly at start up. I can watch how much amperage the AUX batt pulls when the 40A alt. is charging it.

Rick Caldwell
Xenos 0057 5.5 hrs.