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Electrical Schematic Capture Software

keitht

Well Known Member
Getting to the point in the build where I need to get my electrical schematics into shape (from the back of the envelope scribblings) and looking at something better than Visio 2003. I ran across KICAD - it is a open source schematic capture and PCB design tool and while it has some interesting features is pretty straightforward to use and has a comprehensive library of components suplimented with the Digikey library of parts. It runs on Mac,Windows PC and Linux, and the price is right. Worth taking a look if you dont have a current copy of Autocad or the Solidworks schematic capture tools.
KT
 
Use a schematic capture package

For a long time, I had access to an industrial-grade schematic capture package (Altium), but not when I started my RV7 electrical system. I decided to go with Visio since I didn't want to go through the tedious task of making all the symbols for all the component (connectors, pin numbers, etc) or did I want to spend any $$$.

However, now that I'm at the other end of the job, I would do it over with a basic schematic capture package. Though the schematics aren't as "pretty", one of the most useful things you can get from the capture package is a netlist of connections. This is super useful when you're running wires through the ship and routing them to the correct boxes. I had to basically do a manual version of this to make the install efficient. The schematic capture packages do it for free, and maintain it for free.

Find your favorite free version (kicad is good) and spend the time up front; it will pay off in the long run
 

+1 on that. Have done all my aircraft schematics using expresssch.

As for KiCad and Eagle... despite developing the precursor to Eagle in the early 80's for integrated circuit design (with a grad student named Corina Lee who wrote the VAX simulation extraction) on a Calma GDS-II system, I hate it. KiCad is better but buggy.

There is no more exquisite torture than learning a new ECAD system... but expresssch is easy.

V
 
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Schematic capture Tools

Thanks for the link to Expresssch. Downloaded it and gave it a try. Very intuative and easy to use took me less than half the time for doing the same schematic in kicad and that was straight out of the box. None of the ? features? of kicad - which is good. Will make the switch to Expresssch.
KT
 
Digikey's SchemeIt is another option, free and online. I did my schematic with it in a few hours.

16460096391_8d4cdc9237_c.jpg
 
I had decided to just go ahead and use a drawing package that I was familiar with (Canvas Draw for Mac) to avoid the learning curve of an unfamiliar CAD program. But I guess I don't understand what a "netlist of connections" is. Is it somehow better than following a trace on your schematic?

I also didn't see having a library of electrical and/or electronic components available would be an advantage. I didn't figure that a significant percentage of the devices wired into an airplane would exist in such a database. I presume that many such devices would have to be created by the user.

The only advantage that I saw was not having to redraw connections when a component was relocated in a schematic.

Please help me understand where I'm wrong and why it's worth the learning curve.
 
Depends how complecated your wiring diagrams are. Having a component library with the components you are using saves a lot of time. Making modifications and corrections is much easier on a schematic capture program. Integrating the functional test of the wiring before applying power and troubleshooting any problems is more straightforward with a cad based schematic. I am not sure the “net list” is really a “must have” for a simple system like an RV. For a heavy transport aircraft it is essential. At what point to spend the extra time learnig a new program is a matter of personal preference. More important to get the wiring diagram correct than to have it look pretty.
Kt
 
By "functional test," are you referring to ExpressSCH's "Check schematic..." command?

Will most of the components I'll be using already in ExpressSch? I see that they have a relay but I haven't studied it well. From a brief look, I almost think I'd need to draw new starter and master relays. How about other components? Do you use the built-in DB connectors? Doesn't look like there'd be room to label the pins.

Edit: Just placed a DB-37. Bigger than I thought. Maybe those would work. But I still wonder about all the other components. I'd love to see somebody's samples from ExpressSCH.
 
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I’ll have to be a contrarian on all this.

I’ve seen a lot of these schematics that are little more than eye charts. Helping an RV-14 builder who chose to use the Van’s wiring harness I found the schematic more frustrating than useful. I just wanted to know what pin goes to what pin.

What I do:
- Document what is in each major wire bundle (as in right wing, left wing, engine and fuselage).
- Document every connector pin, and identify each connector. So I have a list of all the GTN-650 pins and where each wire goes to the next connector. Same for the SkyView 35 pin and so forth. The two 25 pins D connectors that connect the removable panel to the rest of the plane are similarly documented.

This is done on a simple Word document. I find this much easier to work with then trying to follow little squiggling lines on a chart.

This process has worked well on three project when it came to maintenance and/or panel upgrade time.

I realize this is close to sacrilege for a engineer to admit, but I figured someone might be dumping hours into fancy programs when simple could be all that is needed.

Carl

Carl
 
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What I do:...

Carl, I do hear what you're saying and I'm not sure that I won't go in that direction, perhaps in a graphic format.

Here's a complete example, along with source:

Vern, I was just looking at your thread from a few years back this morning and checked out two or three of your PDFs. They look pretty good to me! How do you feel about component theft from your source file? :)
 
Since I was the one to 1st mention ExpressSCH, I'll confess that all I have right now for my build are Carl-like connection lists, in pencil, on a steno pad, and then transcribed into a spreadsheet.

I do firmly believe that both a wiring diagram and connection list(s) are good to have, and intend to eventually create the wiring diagram. But the connection lists were fast to generate, as I was wiring. My build has required somewhat frequent changes/revisions, and it's been easier to to just keep revising a text file.

Charlie
 
Carl, I do hear what you're saying and I'm not sure that I won't go in that direction, perhaps in a graphic format.



Vern, I was just looking at your thread from a few years back this morning and checked out two or three of your PDFs. They look pretty good to me! How do you feel about component theft from your source file? :)


Go ahead, pay it forward.

V
 
The ?functional test? I was refering to was the test steps to check out the wiring, power up all the components, activate firmware and software and then ensure the system functions as intended. Just having a wire list in word or excel is a good first step but likely to come up short when you have powered up all the components and can?t get everything to play together. Having a detailed wiring diagram makes troubleshooting much easier under those conditions. If you are bringing up a predominantly Dynon system with Garmin components are you going to just do a continuity test for all the cable harnesses, plug it all together and hit the power switch or bring the system up sequentially in easy stages. It?s important to have a written plan that is followed to minimize errors and component damage resulting from such errors. Additionally, a written plan with troubleshooting ?breakout? steps reduces the risk of ?winging it? and improvising in the heat of the battle and blowing up some expensive avionics.
KT
 
Thanks, Keith. Makes sense and sounds like a good plan to follow. Now, if I can just exercise enough forethought... :)
 
I?ll have to be a contrarian on all this.

I?ve seen a lot of these schematics that are little more than eye charts. Helping an RV-14 builder who choose to use the Van?s wiring harness I found the schematic more frustrating than useful. I just wanted to know what pin goes to what pin.

What I do:
- Document what is in each major wire bundle (as in right wing, left wing, engine and fuselage).
- Document every connector pin, and identify each connector. So I have a list of all the GTN-650 pins and where each wire goes to the next connector. Same for the SkyView 35 pin and so forth. The two 25 pins D connectors that connect the removable panel to the rest of the plane are similarly documented.

This is done on a simple Word document. I find this much easier to work with then trying to follow little squiggling lines on a chart.

This process has worked well on three project when it came to maintenance and/or panel upgrade time.

I realize this is close to sacrilege for a engineer to admit, but I figured someone might be dumping hours into fancy programs when simple could be all that is needed.

Carl

Carl

When I built my RV-10 many years ago, like Carl, I documented each and every connection in Excel. I also created a tab for each avionic device.

The end result is that you can look at P1 on my GTN650 and see what pin each wire is connected to, the pin/connector/device at the other end, as well as any required software settings to make that connection.

Fast forward to today. I had intended making nice schematics after I started flying. It's been over five years and I still haven't got around to it yet. With that said, I have that Excel wirebook on a laptop in the hangar, on my iPad, and on my iPhone. I refer back to it all the time or when I need to make a change. It has served me well.

I'm not saying to not draw a schematic, just that sometimes simple approaches work well too.

bob
 
When I built my RV-10 many years ago, like Carl, I documented each and every connection in Excel. I also created a tab for each avionic device.

The end result is that you can look at P1 on my GTN650 and see what pin each wire is connected to, the pin/connector/device at the other end, as well as any required software settings to make that connection.

Fast forward to today. I had intended making nice schematics after I started flying. It's been over five years and I still haven't got around to it yet. With that said, I have that Excel wirebook on a laptop in the hangar, on my iPad, and on my iPhone. I refer back to it all the time or when I need to make a change. It has served me well.

I'm not saying to not draw a schematic, just that sometimes simple approaches work well too.

bob

To build on Bob's comments... I opted to do my wiring diagrams on a "system" basis, with each aircraft system laid out on an 8 1/2 x 11 page of quad-ruled paper. My wiring diagram is drawn in pencil, old style. Zero cost, zero learning curve, zero probability of software incompatibility etc, and I never have to worry about a hard disk crashing! I then photocopy the finished drawing and scan the drawing. The photocopy produces a "hard" image that is placed into two binders, one that stays at the hangar, and one that stays at home for reference. The scans are on a USB stick that stays in the airplane and are stored on the tablet I use to run navigation apps so I have ready access while away from home.

Now what's this "system" approach? It's really simple and makes troubleshooting dead-easy. Let's take external lighting as an example of a system. The wiring diagram captures everything to do with external lighting, starting at the Main DC bus, through the circuit breaker(s), switch(es), wing root terminal blocks where, for instance, a single "NAV LIGHT POWER" wire splits to "LEFT NAV LIGHT POWER" and "RIGHT NAV LIGHT POWER", ultimately terminating at each nav light. Every connector and connector pin is detailed. When you have trouble with the nav lights, you are now troubleshooting from a single page diagram.

I've spent a lifetime troubleshooting aircraft electrics and avionics. So far this "system based" approach to wiring diagrams has proven to be the most effective.

Oh, one other point. VERSION CONTROL is important. Remember I said that I do things in pencil and paper? This allows easy editing. The drawing has a date box that is updated with every edit. Once edited, the new photocopied versions go into the binder, onto the memory stick and into the tablet. The previous photocopied version in the "home" binder gets a line through it and the word "Superseded" written across it, but it is kept in the binder behind the current version. This allows you to see the evolution of the system, from original, through to "as built" through to "as modified when I installed new equipment." It's a system that works very well and costs virtually nothing, while giving both a current view of the wiring as well as a full historical perspective of its development.
 
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