MobBob – Armed… and still not dangerous

06 MobBobArms - Assembled 01
I’ve created some new 3D printable parts that let you add arms to MobBob V2.

The parts can be downloaded from Thingiverse here:


01 MobBobArms - New Parts


The “Socket” parts mount on either side to provide peg holes for MobBob’s shoulders. These are designed to fit onto the mounting holes introduced in MobBob V2. (You can unscrew an existing MobBob V2 and add these parts in.)


03 MobBobArms - Arms Sockets 0202 MobBobArms - Arms Sockets 01
04 MobBobArms - Arms Sockets 03


I’m planning to created some fully 3D printable arms, but I have not done that yet. (However, I’ve provided a template for the pegs to enable others to create their own arms if they wish!)


While I haven’t provided printable arms, I’ve did upload a shoulder piece that features a Lego Technics compatible beam. That piece enables you to make arms using Lego Technics pieces.


I’ve made 2 sample arms using Technics pieces. One is a static arm with a poseable claw. The other arm has a Sharp IR Distance sensor attached.


05 MobBobArms - Arms on connectors


The IR Sensor arm has a hinge at its wrist to enable it to be aimed up and down. I thought this might enable it to be aimed up for wall detection and aimed down for edge detection (so he doesn’t walk off tables).


I originally planned to 3D print a Lego-Technics compatible mount for the IR sensor, but decided to see if I could attach it without doing that… I thought that if it was doable, then it shows that users (especially kids) could attach new sensors fairly easily using Lego parts. I did have to use some rubber bands though!


Here are some pictures of MobBob with the arms attached.


08 MobBobArms - Assembled 03  07 MobBobArms - Assembled 02


To support the Sharp IR Sensor (and other future sensors), I’ve added 2 connectors to the Bluno Beetle. These connectors have 3 wires, providing 5V, Gnd, and an Analog pin. These connectors can be used with a wide variety of sensors, and should enable different sensors to be swapped in fairly easily.


09 MobBobArms - Assembled 04


The arms can be plugged in and pulled off easily. I wanted to make it easy to swap the arms so that users can use different arms with different functions. E.g. Arms with different sensors, arms with a servo-driven claws, etc.


For the same reason, I added connectors instead of soldering the Sharp IR sensor directly to the board. I wanted it to be easy to connect different sensors to the Bluno board.


I’m hoping that the addition of interchangeable arms can make MobBob a platform for experimenting with and learning about different sensors.


I haven’t updated the software yet so I can’t demonstrate the new IR sensor in action. However, I will be updating the Arduino code and the Android app to support the Sharp IR sensor. I’ll post a video once I have it working.

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