Looking for input...I'm clueless

cjensen · Post by **cjensen** » Sat May 17, 2008 11:28 pm

Okay, I do admit I don't have a clue when it comes to wiring my airplane, even though I've been to the Aero Electric seminar. That being said, I do know how to sort of read schematics, but in designing my own, it's a steep curve.

So, I borrowed Bill Repucci's design to make my own, and here's what I came up with...

Main bus-

Avionics bus-

Always hot bus-

And Pmags schematic-

Please feel free to critique this, as these are my first drafts, and first shot at ever designing a wiring schematic.

Thoughts, ideas, is it silly? I made it, but now what do I do with it?

jim_geo · Post by **jim_geo** » Sun May 18, 2008 12:32 am

I'm going to ask why the keep alive buss? I'm not familiar with the Enigma and it's keep alive function. Keeping a clock running would be the only reason I can think of for having a keep alive circuit. I was sold at first on having a keep alive circuit even though it meant having a buss hot all the time which I wasn't thrilled about. Now, I'm using Dynon for both my EFIS and EMS so our reasoning may be different. I started reading posts about batteries being run down pretty fast while keeping a Dynon alive and I started loosing interest in the keep alive buss. Especially after realizing that my GPS will upload time information to the EFIS when I turn them on together. Hard for me to imagine your Enigma wont do the same. I'm just thinking that I'd rather not have any live wires in the cabin while I'm not supervising it's activity. I suppose in my perfect world my hot battery terminal would also serve as an 80 amp fuse.

Picture from about a week ago. It still looks pretty much the same.

markb · Post by **markb** » Sun May 18, 2008 3:10 am

Check the connections to your master and starter relays. The master relay has the battery connected to the coil rather than the contact. And the wires to the coil and contact are reversed on the starter relay.

I believe standard practice is to NOT switch the starter power through the master relay. The master relay is not designed to handle the high current of the starter.

Your filter capacitor should be tied from the avionics bus to ground. BTW, the capacitor is a potential point of failure. If it happens to short out, you will lose your avionics bus, maybe even your main bus, unless the avionics bus SPST switch is really a circuit breaker. (If it's not, the shorted filter capacitor would not be fused, which could lead to fireworks.)

Doesn't the Enigma have an optional backup battery? If so, that might be a better option than the "always hot" bus. Better if you can eliminate as much unfused wiring as possible. (BTW, the "always hot" bus is shown connected to the Main bus on page 3, but to the battery on page 1.)

What about your defroster? It looks like you have two elements in series, you probably meant for them to be in parallel. And my guess is they need a lot bigger fuse than 5 amps. (5 amps at 12 volts is only 60 watts).

Your drawings look nice, what software did you use?

Brantel · Post by **Brantel** » Sun May 18, 2008 7:17 am

markb wrote:Check the connections to your master and starter relays. The master relay has the battery connected to the coil rather than the contact. And the wires to the coil and contact are reversed on the starter relay.

I believe standard practice is to NOT switch the starter power through the master relay. The master relay is not designed to handle the high current of the starter.?

The master just needs its input to the contact connected to the battery. It is common to switch the ground side of the coil on aircraft masters.

It is also "common" practice to put the starter after the master. Van's plans show you to do it this way and how many spam cans have you been in that would turn over without the master on?

The starter relay needs the coil's hot connection disconnected from the contact's hot connection. The power from the master needs to go to the contact's hot connection and move the lead from the switch to the coil's hot connection.

That was all I had time to look at, I will look at more later.

weezbad · Post by **weezbad** » Sun May 18, 2008 7:41 am

are you using a permanent magnet starter (they are small lightweight ) sky tec or the like. if so vans reccomends running an actuation wire or the diss-engagement will be prolonged....many people ignore this but its only 18" of wire. no it does not mean the wire from your f/wall mount solenoid to the starter will always be hot. you will simply have two solenoids coming on at the same time.

painless · Post by **painless** » Sun May 18, 2008 9:29 am

Are you going with manual flaps? I didn't see electric ones in your diagram.

Ever think of an essential buss? In case of an alternator failure, you can cut back on draw by switching to it and have things like comm, flaps, etc on it. Ala Bob Nichols.

Post by **bullojm1** » Sun May 18, 2008 9:57 am

painless wrote:Are you going with manual flaps? I didn't see electric ones in your diagram.

Ever think of an essential buss? In case of an alternator failure, you can cut back on draw by switching to it and have things like comm, flaps, etc on it. Ala Bob Nichols.

Actually, the point of the endurance bus is to keep giving you power in case your master contactor fails. In case your alternator fails, just start turning stuff off! Mostly everything has a power on/off switch.

painless · Post by **painless** » Sun May 18, 2008 1:12 pm

bullojm1 wrote:
Actually, the point of the endurance bus is to keep giving you power in case your master contactor fails. In case your alternator fails, just start turning stuff off! Mostly everything has a power on/off switch.

Guess I am just lazy...

One switch and I am done powering down.

cjensen · Post by **cjensen** » Sun May 18, 2008 2:18 pm

jim_geo wrote:I'm going to ask why the keep alive buss? I'm not familiar with the Enigma and it's keep alive function.

I'm not sure on that yet, but I thought I'd go ahead an make one that I can make changes to if I need it. I haven't read thru the entire Enigma manual yet to know for sure if I need it. It does have a battery backup option though.

cjensen · Post by **cjensen** » Sun May 18, 2008 2:32 pm

markb wrote:Check the connections to your master and starter relays. The master relay has the battery connected to the coil rather than the contact. And the wires to the coil and contact are reversed on the starter relay.

I'll make the change. This is why I want others to look at it...

markb wrote:I believe standard practice is to NOT switch the starter power through the master relay. The master relay is not designed to handle the high current of the starter.

Will check...I have no idea.

markb wrote:Your filter capacitor should be tied from the avionics bus to ground. BTW, the capacitor is a potential point of failure. If it happens to short out, you will lose your avionics bus, maybe even your main bus, unless the avionics bus SPST switch is really a circuit breaker. (If it's not, the shorted filter capacitor would not be fused, which could lead to fireworks.)

Got it. Good to know.

markb wrote:Doesn't the Enigma have an optional backup battery? If so, that might be a better option than the "always hot" bus. Better if you can eliminate as much unfused wiring as possible. (BTW, the "always hot" bus is shown connected to the Main bus on page 3, but to the battery on page 1.)

Yes it does, and I may change that. I don't know that I want an always hot bus or not, and may do away with it altogether.

markb wrote:What about your defroster? It looks like you have two elements in series, you probably meant for them to be in parallel. And my guess is they need a lot bigger fuse than 5 amps. (5 amps at 12 volts is only 60 watts).

I have two mini computer fans to use as defrosters, but they are not installed yet, and I haven't made the final call on those yet. They are very minimal on power needs I think.

What kind of symbol is used for putting things in parallel?

markb wrote:Your drawings look nice, what software did you use?

Thanks! I used a freebie computer PC board design software called ExpressPCB/ExpressSCH. The SCH is the one I used. Do a search for it, and download it. I've just been tinkering with it to try and learn it.

cjensen · Post by **cjensen** » Sun May 18, 2008 2:35 pm

weezbad wrote:are you using a permanent magnet starter (they are small lightweight ) sky tec or the like. if so vans reccomends running an actuation wire or the diss-engagement will be prolonged....many people ignore this but its only 18" of wire. no it does not mean the wire from your f/wall mount solenoid to the starter will always be hot. you will simply have two solenoids coming on at the same time.

I will probably use a heavier starter to add a little weight up front since I'm using the 320 engine.

cjensen · Post by **cjensen** » Sun May 18, 2008 2:37 pm

painless wrote:Are you going with manual flaps? I didn't see electric ones in your diagram.

Yep, manual...no need for more electrons.

painless wrote:Ever think of an essential buss?

Yeah, I may just use the schematic from Nuckolls on dual Pmags on a budget if I do that.

weezbad · Post by **weezbad** » Sun May 18, 2008 7:29 pm

cjensen wrote:
weezbad wrote:are you using a permanent magnet starter (they are small lightweight ) sky tec or the like. if so vans reccomends running an actuation wire or the diss-engagement will be prolonged....many people ignore this but its only 18" of wire. no it does not mean the wire from your f/wall mount solenoid to the starter will always be hot. you will simply have two solenoids coming on at the same time.
I will probably use a heavier starter to add a little weight up front since I'm using the 320 engine.

i may need a big Prestolite starter as well. but man those things are gignormus

cjensen · Post by **cjensen** » Sun May 18, 2008 8:33 pm

Yeah, but it's functional weight, rather than dead weight like lead or something.

weezbad · Post by **weezbad** » Mon May 19, 2008 6:44 am

cjensen wrote:Yeah, but it's functional weight, rather than dead weight like lead or something.

oh im not knocking it. i could'nt imagine a better way to ballast it..it mounts perfectly, out of the way, has good use and you know it's old school durable.. beats the hell out of a prop weight but you may need one of those as well.

cjensen · Post by **cjensen** » Mon May 19, 2008 8:32 am

weezbad wrote:it mounts perfectly, out of the way, has good use and you know it's old school durable.. beats the hell out of a prop weight but you may need one of those as well.

You bet it does! It won't surprise me if I need a little more up front, however, if I compard the weights on the O-360 and O-320 from G&N that I would use, there's only 5 pounds difference in dry weight, so I would guess that either engine will need more weight, or both will be fine...

Post by **bullojm1** » Mon May 19, 2008 9:13 am

Chad-

I noticed you had both PMAG's connected to the Main Battery Bus. Bob Nuckolls mentions plugging them into the "Always Hot Bus" instead of the main battery bus. This is done in case the master relay stops working, your PMAG's still have power.

Now, I do know the PMAG's have internal generators so the master relay failing isn't very critical, but why not have some belt and suspenders?

cjensen · Post by **cjensen** » Mon May 19, 2008 1:04 pm

Does Nuckolls call it "Always Hot" or is that the Essential bus?

Post by **bullojm1** » Mon May 19, 2008 2:23 pm

cjensen wrote:Does Nuckolls call it "Always Hot" or is that the Essential bus?

Here are Nuckolls Definitions:

Battery Bus - The Bus connected directly to the Battery, AKA Always Hot.

Main Bus - The Bus connected to the battery via the master contactor.

Endurance Bus (aka essential bus aka E-BUS) - A bus that is connected with a diode to the main bus. If the master contactor fails, there is a switch used to connect the E-Bus to the battery bus, which allows the continual use of the devices on the E-BUS in the case of the master contactor fails.

Appendix Z (http://www.aeroelectric.com/articles/Re ... Z_R11M.pdf) should clear things up. Figure Z-13/8 shows how he recommends connections PMAG's. Actually, this diagram is more updated than the one I have - it shows a EMAG on the battery bus, and a PMAG on the main bus. I guess that makes sense - putting the mags feed on two different busses in case one of the busses shorts out.

Another question I have is about the stereo plug...whats the purpose of that?

cjensen · Post by **cjensen** » Mon May 19, 2008 2:30 pm

bullojm1 wrote:
Appendix Z (http://www.aeroelectric.com/articles/Re ... Z_R11M.pdf) should clear things up. Figure Z-13/8 shows how he recommends connections PMAG's. Actually, this diagram is more updated than the one I have - it shows a EMAG on the battery bus, and a PMAG on the main bus. I guess that makes sense - putting the mags feed on two different busses in case one of the busses shorts out.

Another question I have is about the stereo plug...whats the purpose of that?

Thank you Mike!

That newer Z-13/8 is the one I just printed out over the weekend that I may just use over what I've designed.

The plug would serve as a sort of "kill switch" on the ground to completely disable the Pmags. Would prevent an accidental spark if the prop were turned, and theft.