Panel Layout Finished

[jjbardell]

New version since my last one was a mess.

Looking forward to comments!
A special thanks to Bill and Robbie this week for all help. :D
Have a great day all.

[Rynoth]

Josh, nice work! Some questions I've come up with after reviewing your schematics:

1.) I don't see fuse call-outs in your diagrams, though most of your switches are switch/breakers. The real question is, are all your wires protected? For example, the hot 18 GA wire that runs from the battery to the 10A breaker switch (Elec Ignition), will it have a fuse on the battery side (fwd of firewall) in case the wire shorts somewhere between the battery and the switch on the panel? I would be wary of ANY wire inside the cockpit that does not have circuit protection between the cockpit and the battery/pwr source.

2.) I don't see a switch depicted that actuates the master solenoid. I see a 20GA wire that runs from the master solenoid to the 30A master breaker switch, but 30A is WAY too much for a 20GA wire. My assumption is that the 20GA wire is the grounding wire for the solenoid, but in this case, how does power flow from the master solenoid to the rest of the system? (it's not obvious in your diagram.)

3.) In your first diagram, you show wires running from the battery to a bunch of breaker switches, but I reckon those wires are actually running from the master solenoid instead? It's hard to tell what is switched on/off when the master solenoid is switched on/off.

I do have some more observations but those are ones that stand out the first time I look at it. I must have spent 30+ hours studying and re-doing my electrical schematics and found that I quite enjoyed the process, so I'm happy to help troubleshoot.

For what it's worth, here's a link to my setup, though some minor tweaks have been made since this post. I used fuse blocks (no breakers) so it probably looks a lot different than yours: http://www.rynoth.com/wordpress/waiex/2 ... -planning/

[jjbardell]

Thanks Ryan. I am going back to the drawing board and going to make some adjustments. Send you a PM.

[sonex1374]

Just a few thoughts to go along with the feedback from Ryan....

- Do you really need a switch on your iEfis, or is the Avionics master switch good enough? Is there ever a time where you want to power up the panel lights, comm and transponder, and maybe a USB plug but really want the iEfis off (besides just fuse/CB protecting the circuit)? I know this is airplane herrasy, but how often do you selectively power up the various electronics in your car? If 99.9% of the time you'll switch on the Avionics Master, then immediately the iEfis switch, why have two switches at all?

- You may want a way to turn off or isolate your alternator output. Consider adding a switch between the regulator and battery/battery contactor, or an alternator disconnect relay controled by a switch.

- You might need power to a fuel level probe, or a fuel flow transducer (e.g. Red Cube). You'll need room on your power bus for that, and perhaps a fuse.

- 3 amp breaker on your iEfis/RDAC/SP-6 combo might be too low. Could need somthing like 5 amp?

- 1 amp on your fuel pump might pop as a nuisance when it first starts up (due to the initial surge). Might change this to 3 amp. Remember, the fuse/breaker protects the wire, and isn't really sized to just barely meet the load of the device connected to the wire.

- You might want to add 12V cigarette lighter plugs? Those could be connected directly to the barrery (always hot) or go thru the master switch.

- You might designate the mag kill wires as shielded wire to reduce RF noise.

- You might consider some sort of power filter (or big capacitor) on your alternator output to smooth out any noise.

That's all the initial thoughts :-)

[jjbardell]

Jeff,
Thanks for the insights! I have my comments to your points, so I would love more commentary.

- Since I have the EFIS on the Battery Master, not the Avionics master, I wanted a switch in case I had to power down the avionics during flight in an emergency procedure
- Can you help me understand the switch to isolate the alternator? What is the benefit?
- Good point on the fuel probe. I am not sure if I can tie that in somewhere or if it needs its own fuse. Maybe in inline fuse to save panel space?
- MGL manuals state the 3A is plenty for the Discovery Lite / RDAC / SP-6 together. I thought about a 5A and my bump up
- Good call on the fuel pump. I will bump that to a 3A
- I currently have a dual USB, but maybe I will go back to a cigarette lighter and then plug a dual usb into that. Gives more flexibility
- Good call on the MAG kill wires
- Intrigued on the CAP for the alternator. Any recommendations?

I really appreciate the feedback. Tomorrow I hope to total up all of my continual AMPS to be sure I am not drawing more than 20A. The ADS-B / iPad / iPhone together are a big draw. The iPad by itself isn't, but when it is running Garmin Pilot in Sync Vision with weather and traffic, it is a continual draw on power. :/.

Thanks again!!!!

[fastj22]

Jeff convinced me to do an alternator isolation relay.
Its an automotive relay that allows you to cut one of the phases of the alternator from the regulator. It serves two purposes. If in the case of a runaway regulator, you can cut its power source. A runaway regulator can be dangerous. The second is to allow you to stop charging the buss while in flight to isolate the alternator while troubleshooting noise problems. So if you are experiencing noise or other anomalies, you simply turn off the relay and stop charging the system to see if its the cause.

I think you are fine with 3A on the efis and its components. I run dual Xtremes, RDAC and SP6 on it. I use a 10A on the comm stuff. I also have two 12V cigarette sockets on a 3A to supply my USB plugs. I'm thinking of moving one directly to the battery with inline fuse to allow a ground charger to be plugged into it.

One thing I'd do differently if starting from scratch is to use an automotive fuse block instead of expensive aviation circuit breakers. Cheaper, simpler and very effective.

I also used shielded wiring on everything and pulled all grounds to a common tree of grounds. Nothing is grounded to a convenient spot on the airframe.

Also labeling both ends of the wire is really helpful too.

[gammaxy]

Already some great responses, but this is one of my favorite subjects, so can't resist sharing my opinion too.

I mounted two automotive-style fuse blocks behind the instrument panel along with a bunch of grounding terminals. My original plan was to switch the second fuse block with an avionics switch. My radio (MGL v6) doesn't have a power switch and neither does my EFIS, but I wanted to be able to switch those independently of the avionics bus (requiring 3 switches).

I decided to omit the avionics bus altogether and just have switches for EFIS and Radio (the transponder has a built-in switch). Adding things like fuel senders, etc., is super easy, just add another fuse and hook up the wire. It also greatly reduces the number of connections you have to make when you use CBs with switches.

As was already pointed out, these switches are hardly ever used. I leave them on all the time--even when cranking the engine, since I doubt its possible to damage anything that way. Having those screens lit up until I turn off the master is a good reminder and has prevented me from accidentally draining the battery. I have rebooted the EFIS in flight when troubleshooting problems with a faulty SD card, and have done the same with my radio when the screen mysteriously got corrupted (had to send it back for a replacement screen).



I didn't use a capacitor on the alternator output. In a perfect world, the battery should completely absorb any ripple from the alternator. I took a wait-and-see approach expecting to hear a tone in my headset around the pitch of middle C on the piano (3000rpm * 6 pulses per second / 60 = 300hz) if it were a problem. I haven't heard anything (after >100 hours). I'd still like to hook up an oscilloscope though. I was a little concerned that adding a capacitor would be opening up an unknown failure mode and using up possibly valuable real estate on the firewall for possibly no benefit.

My only significant noise source is my primary (magnetron) ignition. I don't notice it when listening to nearby transmitters, but if they are 10+ miles away, the noise increases until it overshadows the transmission around 20 miles. If I turn off the primary, I get extremely clear reception (no noise at all from secondary ignition or alternator). I didn't follow the plans. I used shielded wire and connected the shield and center conductor to the terminals on the switch, and connected the other ends to the magnetron mounting bolt and P-lead. Now that I think about it, the problem might be that the magnetron mounting bolt isn't grounded very well and might just need a dedicated ground lead (somewhat excited to go try this out now).

[jjbardell]

Chris. What brand of breAker switches are you using? They don't look like Tyco?

[gammaxy]

What brand of breAker switches are you using? They don't look like Tyco?

I'm not using breaker switches--I considered using them for simplicity, but realized there were some items I wouldn't have on a switch but would still need a fuse, so I'd still need a fuse panel/box somewhere.

My switches are made by NKK:
http://www.digikey.com/product-search/e ... 60-1887-ND

[sonex1374]

Josh,

The EFIS might need to be shut down in flight, but would you shut down only the efis and not the comm/transponder? Why not move all the actual avionics to the avaionics switch (efis, compass, rdac, comm, transponder) and power all that with one switch but have each item protected by its own fuse, and move all the other stuff off the avionics switch (fuel pump, lights, USB, 12V sockets). Your avionics switch can power up an avionics bus (using a 6-10 slot fuse block, or a collection of circuit breakers) and control it all with one flip. If you ever had a single device trip the fuse/breaker, it would power down independently and the rest would carry on. I'm not sure there's really a situation where all you want is comm and transponder, and you really really want the efis turned off.

Isolating the alternator might be important if things start to go wrong. Two scenarios come to mind. First, you see an abnormally high voltage and assume that the regulator has partially failed and you're going to fry your avionics with excessive voltage. You'd like to prevent that from happening, so you either 1) disconnect the regulator +12V output from reaching the battery/main bus, or 2) shut down the alternator completely. Option 1 leaves the alternator continuing to supply power to a failing regulator, ultimately overheating it and turning it to slag on your firewall :-( Option 2 shuts off all power generation and allows you to continue your flight on battery power alone. The second scenario is that you're flying along and start to suspect that your battery is running down. You conclude that the alternator/regulator may not be charging the battery. Turning off the alternator/regulator will allow your efis to read the battery voltage without influence from the alternator, allowing you to get some idea of the power left in your battery before things go dark. The failing alternator/regulator might be bumping up the bus voltage just a bit, but not enought to really sustain your battery and electrical devices. Turning it off helps troubleshoot and make a decision.

Inline fuse on the fuel probe is fine. It's such a low-draw device that you won't have any issues with it.

If MGL says 3amp is good for the efis/rdac/sp-6 combo, then I'm sure that's fine. I was just speculating without any real info.

You might do one dual-usb one one side, and a cigarette lighter outlet on the other. Best of both worlds, cause not everything runs on usb 5-volt.

The capacitor or power filter simply provides a bit of filtering to the regulator output to smooth out any noise from getting pumped into the power bus. If you connect the regulator directly to the battery, then any ripples should get soaked up by that. If you connect the output closer to your loads, the battery might not be able to filter everything as easily, and a capacitor or power filter could be useful. You can use a large cap like B&C Specialty sells, or use a commercailly availible power line filter (usually used on CB radios and car stereos).

Your power draw totals are really two seperate things. The averarge draw of your devices in steady-state operation, and the initial draw of a device powering up. Your wires and fuses need to be sized to account for the initial surge of power so you don't burn anything out. This is why conventional wisdom has you use a slightly de-rated amp rating for each wire size so as to allow a little reserve load-carrying capacity for that initial surge. It's more of a problem when selecting fuses or breakers so you don't cut it so close that the fuse or breaker is always popping and becoming a nuisance.

Jeff