FREE Online Schematic tool

By their nature, pilots that fly on their own ruble are always looking to save a dollar here and there. Those of us building planes are usually looking for ways to do things smarter, better, and faster. Put the two together and you tend to wind up with some pretty talented people.

The time came to finalise my as-built electrical schematic and rather than try to hand-draw it a bit of searching online found DigiKey has a free, online tool that will allow you to do any number of drawings, complete with a database of electronic components so it looks just like it came from Stein!

It will export into PDF or PNG format, save it (if you're a registered user) for later use, print and even go so far as to compile a bill of materials for their own webstore, it's a pretty nifty tool all round.

Here's the website, enjoy!

And as a rough example, here's my complete electrical system after around 6 hours of research and drawing - including the first 3 hours lost after I didn't save it... You have the right side SkyView, ADAHRS, GPS and EMS modules, an Xcom VHF and a VP-X Sport as well as 2 PMag's, with all the wiring in the plane shown on the diagram.

AWESOME tool and site. I will be using it a LOT. Thanks for posting the link.

Very Nice - Cheaper than Visio!

I can not find how to identify the wire size/color like a wiring schematic, is that not used anymore?

Also - is there a feature to present this as a series of current flows for practical trouble shooting later?

Thanks for this link it is so much better than pencil!

Here is the US link to it, rather than the Oz one above...

http://www.digikey.com/en/resources/scheme-it

This looks like a very useful and powerful tool for people who want a cloud solution. It looks like you have to create a Digikey account and link it if you want the ability to save things for editing later.

If you'd prefer a standalone solution, ExpressPCB is still free, and runs on Windows platforms (and Linux too, inside the Wine interpreter). Many RV builders have used it and shared part libraries... A search here should pick up some links.

ExpressPCB: http://www.expresspcb.com/expresspcbhtm/download.htm

(not affiliated in any way with either company, but have used ExpressPCB a fair bit)

ExpressPCB is not just good for electronics design and circuit boards. My complete HR-II schematic was done in it.

Example: http://www.vx-aviation.com/sprocket/photos/panel_elec/schematics/TRIM.pdf

Complete pdf and .sch library: http://www.vx-aviation.com/sprocket/photos/panel_elec/schematics/

Having said that, the online Digikey tool is the start of something very big. When they add pcb design with a fab and assembly service then it gets very interesting..

Many aircraft electrical systems switch the negative (grounded) side of the master contactor coil. Doing that has some advantages: Only one long wire is required, not two. The wire runs from local airframe ground to the master switch to the contactor coil. That wire does not have to be fused because the contactor coil limits the current. Another advantage is that no always-hot wires go into the cockpit. In the event of an imminent forced landing (crash), all electrical power can be shut off near the battery, minimizing sparking that could lead to a fire.

Mich48041 said:

Many aircraft electrical systems switch the negative (grounded) side of the master contactor coil. Doing that has some advantages: Only one long wire is required, not two. The wire runs from local airframe ground to the master switch to the contactor coil. That wire does not have to be fused because the contactor coil limits the current. Another advantage is that no always-hot wires go into the cockpit. In the event of an imminent forced landing (crash), all electrical power can be shut off near the battery, minimizing sparking that could lead to a fire.

Click to expand...

Good on ya Mich. I had often wondered if there was a way to avoid the always-hot and unfused wire running into the cockpit - amazing how I overlooked such a simple solution...

I'll be changing out that wiring next time I'm in the Mancave to switch the grounded side of the contactor.

EDIT: It's a good thing I don't have much hair left of I'd really feel like I was having a blonde moment...The standard Vans Master relay already grounds the coil to close it. The 12V-energised wire that runs from the cockpit is for the starter relay. Schematic fixed and crisis averted!

Another option, that I haven't had an opportunity to fiddle with is MultiSimBlue from Mouser which is free when you register an account.

That is a great tool and we often recommend folks use it (or variations that exist of that offering from other folks as well)...as we really don't like to do airframe power diagrams for folks.

We normally do avionics interconnect drawings which are quite a lot more complicated and need to be customized based on equipment and interfaces (most of which is not the case on airframe wiring which is typically just a power/ground schematic). As noted though, little things like that master contactor can get you if you don't realize it or didn't know it.

Cheers,
Stein

AutoCAD, anyone?

AutoCAD works pretty well for this as well. I have started my diagram, adding to it as I make decisions about components, lights, etc. One probably would not want to buy it just for this purpose, as it is a bit expensive, but if you already have and use it, it works fine, and is easy to edit or revise as necessary. You can easily make the lines match the colors of the various wires, and line widths can be varied to indicate different wire sizes if you like. And, you can print all or part of the diagram to use while installing the wiring, to any scale and paper size combination you prefer.