We finish out our build by 3D Printing our sensor brackets and brain box enclosure.


When designing 3D printed parts with Autodesk Fusion, we always follow these rules:

  • Start with Sketches
    • You can go back and edit your very first sketch to improve your components 100 features down the timeline.  So, we always start with a 2D sketch to extrude out a 3D part.
  • Create the obstruction geometries first:
    • This sets the scale of your components.
    • We use the term "obstruction geometry" at work to mean the minimal geometric shapes to satisfy the design file.
    • In the Trike Build, this was the trike frame tubes, batteries, and motors.  Our parts had to be installed on them, so we had to have "obstruction" geometries on which to build from.
    • The intent is to ensure your 3D part you are making will be perfect - not the obstruction geometry.  So, I don't waste a lot of time making obstruction geometries pretty.  I save that time for game assets
  • Always consider printing and assembly:
    • I always consider how I can break my prints into multiple pieces, even if it means gluing them together after.
    • Many parts could be printed as full object.  For hobby 3D printers and inexpensive filament, the likelihood that your printer or filament will pull off a big complex print the first time can be a gamble.  When it does do it, the power goes off in a storm with 1/8" to go.
    • To pull this off, I design the full part, then split the body at logical locations.
  • Convert Bodies to Components ASAP
    • As soon as a body forms, I flip it to a component and nest it in the appropriate part of the hierarchy.
    • This allows for quick 2D drafting exports and better organization of the design file for complex projects
  • Holes are modelled, but very small
    • I always model in holes for fasteners versus drilling by "eye" later.  However, I make them smaller than intended to get perfect points to drill.  I don't make them so small that I will end up drilling out the shell around the hole into the "honeycomb" of the part.  I've found that the accuracy of my 3D printer is all that great for hole printing.  I'm better to physically measure the fastener and select the matching drill bit and drill it true versus rely on the print.
  • Never, ever delete anything
    • Since features build upon one another, if you delete something, it most likely will sever the timeline taking away the power of Autodesk Fusion.  Instead, just "remove" whatever it is that is bugging you and its definition will stay.


You can get the Autodesk Fusion 3D files from our GitHub at the following address:



  • Speed sensor and Interlock

The speed sensor is used to interlock the motor if not going at a sufficient speed.  This is to ensure the throttle doesn't trigger the motor if the rider isn't ready.  A person could get seriously hurt if it took off with their feet planted to the ground.  The other benefit is that we get to record top speed travelled to our SD card and cut the motor off if we are going faster than we deem our rider should go based on their skill level.

Ultimate Smart Trike Speed Sensor

  • Pedal Sensor and Interlock

The pedal sensor is used to interlock the motor if the rider stops pedaling for any reason.  We still want to get exercise.  If we stop pedaling, the MKR1000 will assume we want to stop or want to be riding with extra caution.  Again, this double ensures that we won't start the throttle while our feet are not on the pedals which would surely cause injury.  It has a hall effect sensor and a rare earth magnet stuck to the pedal to switch the sensor - no glue required :-).

Ultimate Smart Trike Pedal Sensor

  • Proximity Sensor and Interlock

This proximity sensor will interlock the motor if anything is in front of the trike.  We don't want the motor to contribute energy into a collision.

Ultimate Smart Trike Proximity Sensor

  • Garage Door Opener Receiver

The garage door opener receiver is a clever hack on a standard push button garage opener.  We built it a year ago.  We took apart an old opener and simply use a microcontroller to simulate the button press.  The microcontroller receives its trigger through either the IP camera built in web server or through webhook triggered by the MKR1000.  That device merits a project vlog of its own.

Ultimate Smart Trike Garage Door Receiver

  • Braking Limit Switch and Interlock

The braking limit switch uses the physics of the motion of the brake lever pull on our new hydraulic brake to touch a limit switch.  This signals the MKR1000 to interlock the motor.  No more panicking and holding the brake and running the motor at the same time!  This feature wasn't shown in the video above, but hopefully it will show in a later release to YouTube.  It's one of the top two important interlocks.

Ultimate Smart Trike Braking Sensor

  • Tilt Sensor and Interlock

The tilt sensor simply soldered to the main circuit board provides the final interlock.  If going down a hill the motor will be cut off - or if the trike flips over.

Ultimate Smart Trike Tilt Sensor

  • SD Card Output

For every interlock tripped or new high speed, we write out to a file.  This allows us to study the sensor data to calibrate for best ride quality and safety.

Ultimate Smart Trike SD Card File



This concludes our blog for Design for a Cause.  We really love the way it turned out.  Here are our favorite features:

  • Interlocks:  It will not injure a human being or, through inaction, allow a human being to come to harm.
  • Garage Opener:  It will obey the orders given it by human beings except where such orders would conflict with the First Law.
  • Fail Safe Relay:  It must protect its own existence as long as such protection does not conflict with the First or Second Laws.  In this case, if the MKR1000 circuit fails, the relay kills the motor through its physical design.


Also, we priced a major brand trike that is 36V.  It has a $2995 MSRP.  We have $900 for ours with a lot more smarts and battery life.


But, we still have more to go:

  • Calorie counter:  We need to research an approach to calculate calorie burn from the pedal count.  This most likely will be dependent on one's weight, so that will take additional levels to program into the menu functionality.
  • Seated Garage Opening:  The throttle has an on/off button that we haven't wired to anything.  We plan to wire this to trigger the garage versus have to do it only through the menu.
  • Lower the Center of Gravity:   on our Raising Awesome Channel, we will weld in the battery brackets that will locate the batteries under the trike.  This will take the center of gravity as low as it can go and move it under the rider for added stability.
  • Front and Rear Lights:  with all that battery power, why not?
  • Trim and Decals:  to make it epic, we'll cut custom vinyl labels for the tubes.  We'll also use add some panels to cover up the moving parts.


What would you name it?

How would you improve the design? 

Have you ever combined electronics with mechanics to make a useful build? 

Have you ever Designed for a Cause?


Comment below - perhaps we'll include you in a future YouTube video with your idea!


-Sean, Brenda, and Connor   -    Raising Awesome


Ultimate Smart Trike Sean and Connor from Raising Awesome