In the previous post about Sensors for the Rover Bot, I discussed some of the shortcomings of the whisker-type bump switches used. While they did an ‘ok’ job, they persistently got hooked on the edges of objects from which the rover was moving away.
This became frustrating enough that I decided to design and make a Better Bump Switch.
I had a few design goals in mind:
- Avoid the ‘catch’ on reversing, my major point of frustration with the whiskers.
- Use cheap and off-the-shelf hardware if possible. I have a lot of tact switches in my stash (and they are very cheap) and a collection of springs recovered from various broken equipment.
- Make the design scalable to different dimensions (height, width, depth), within reason, as these are parameters that are likely to change between robot types.
- Make the design 3D printable with minimal materials.
The design I came up with is a hinged flap with an internal spring actuator that activates the tact switch, shown below.
Designed in Fusion360, this is a fully parametric design that allows changes to most of the model dimensions – certainly more than just length, width and depth.
The Fusion360 model, IGES and STL files for this bump switch assembly are available from my Thingiverse repository.
The spring and tact switch are held in place using hot glue or CA glue, and the hinge is made by sliding a 1mm wire through the hinge pivot hole. As designed the mounting hardware is an M3 nut and bolt.
A completed bump switch is shown below. These do work a lot better than the whisker type in my application and I have happily switched over to this new design for my Rover bot.