RC Plane Autopilot (Fusion 360 Electrical Design Tutorial)

This tutorial will show you how to use the electrical design branch of Fusion 360, and the basics of tinkercad circuits to design an autopilot based on the ATtiny85 IC and the GY521 gyroscope+accelerometer.

Required:

• Autodesk account
• Computer

Optional:

• ATtiny 85
• Pin headers
• 3 axis gyroscope + accelerometer
• prototyping Board or PCB manufacturer

When designing an electronic circuit, I like to first design it in the Tinkercad circuit workspace, and then design it in a more complex program like Fusion 360. In order to access all of the parts in Tinkercad, click on the dropdown above the components and choose "All". Start By dragging out a Small Breadboard, and Below that, an ATtiny. Place the ATtiny across the middle of the Breadboard as showen.

Drag out 3 servos to represent an ESC and the controlling servos. Wire the brown to ground, red to +5v, and orange to PB1, PB3, and PB4 on the ATtiny. Attach the +5v pin on the ATtiny to power and ground to ground. Finally, because Tinkercad doesn't have a gyroscope board like we will be using, add an 8 pin header. Connect pin1 to +5v, pin2 to ground, pin3 to PB2, and pin4 to PB0.

This is the completed circuit, but it leaves a pin on the ATtiny free so there is some room for expansion.

Also having a basic knowledge of the parts your using and pinout diagrams at the ready is very helpful.

Open Fusion 360, and create a new sketch by clicking on the Create Sketch button in the top left corner. Then select a work plane to start on. Finally, click on the rectangle in the toolbar and create a rectangle of about 100mm by 50mm. Once you have your rectangle, click on "finish sketch".

Next, click on "extrude" and pull it about 2-5mm. Click on the dropdown labeled create, and navigate to "Create 3D PCB". Click on the top of the rectangle and it will add a new tab at the top of the screen. Now there should be a button labeled "Push to 2D PCB" where the extrude button was. when you click on that, a box saying "No linked PCB 2D document exists, Do you still wish to continue?" You want to click yes and another tab will be opened. This is the PCB design space.

Personally, I prefer to turn on the grid when I start a New PCB because it helps with part placement and when routing wires. To do this (I tried to show this but Instructables crops the images so now you cant see it) Click on "Grid" in the top left, and change it from off to on. Keep the grid size 50.

Next, to add parts, click on the drop-down menu labeled "place" and click "Add Part". In the search menu, type 'DIP' and hit enter. This will search for all Dual Inline Packages. I am using the IC labeled P(R-PDIP-T8) (version 3) because that's the closest in dimensions to ATtiny 85. Click on it and click OK. This will make a version of it follow your mouse and snap to the grid. Click when you have it where you want and it will place it then click OK in the top right box.

Next, go back to the Parts menu and delete the search, then go to the connectors dropdown and select "1x01". Place 3 columns of 3 pins for the servos, and a row of 4 for the accelerometer + gyro. Finally, place two more in a column for +5v and GND.

This Part is easier If you have your tinkercad drawing up.

Click- connects a signal to a part

Double Click- ends the signal

Start like your going to add a part but instead of clicking on "add part", click "Signal." Click on the bottom pin of the servo connectors and a wire will connect them. You want to connect this with the third pin of the gyro pins and the bottom left pin of the ATtiny for GND. All 5 pins should then be connected by a white line. This is the GND wire. Connect this to the bottom of the two power pins. Next, connect the middle servo pins with the fourth gyro pin and the top right ATtiny pin. This is the 5v wire. Next, for the signal pins, use the Tinkercad drawing for reference and connect the top pins of the servo connectors to the middle 2 left ATtiny pins and the middle bottom right. Connect pin1 of the gyro pins to the bottom right ATtiny pin and pin2 to the top middle.

The hardest part is over (yay!)

Simply click and drag on the parts to move them so they're closer together.

Finally, click on the dropdown labeled "Quick Route" and navigate to "autorouter". By changing the effort level you can tell how many different routes for it to look for. Click continue and then click start. After a few seconds, click through the different options and choose the one with the least blue wires under the ATtiny (for something later).

Red: Top of PCB

Blue: Bottom of PCB

Click on "grid" again and change the size to 25.

Scroll out and select the edges of the board and delete them. Then click on "Outline Polyline" above "Board Shape". Make sure to give enough space between the components and the edge.

If there are still wires under the ATtiny, click on "rip up" and rip up the portion of blue wire in the way.

Make sure the air wire is still there. If it is not, place an airwire between the two ends of the wire.

First, click on the dropdown labeled 20 dimensions and change it to 16 bottoms. This makes it so any changes are made to the bottom layer instead of the top.

Click on "route manual" above "route". Select one end of the airwire and draw the wire as close to the edge as it will let you. connect the two ends and click "ok" in the box.

At the very top near the tabs, there is a button labeled "Document" click on this. Go to the dropdown labeled "draw" and select "Text". Write any text you want in the box and adjust the size and angle so it fits what you need. Just click and it's on the board.

Finally, in the top left, click on view in 3D PCB and it will send you to the middle tab again. This will generate a 3D model of the completed PCB.