The robot box needs to know when it has reached the limit of it’s motion. If motion continues past this point, the machine will literally rip itself apart. To stop this happening, I am using a limit switch that will be pressed if the robotic finger move too far. However, it seemed that a good portion of the time the robot would ignore this button and continue to rip itself apart. The reason for this lies in the way I was using interrupts to detect the pressing of the button.
For the Robox project, I needed a board to program and control a servo and a DC motor – I could probably have used something off-the-shelf, but I prefer to have a board specialised for the job.
The board I designed features an ATtiny828 microcontroller with 16 general use IO, two PWM outputs to control two 6V servos and an Allegro A3916 dual h-bridge to control two DC motors (or one stepper motor) at up to 1A per channel. This is more of a general use motor control board and could be useful in a bunch of projects.
In my previous post I talked about modifying the gearbox of a continuous servo motor so that it span faster, albeit with lower torque. Since then I have been fighting with a new issue that was proving to be a show stopper. The issue is demonstrated in this video:
I needed a servo for the robotic finger so that it could go forwards and backwards in a controlled manner to push the switches. Servos normally have limited rotation e.g. 180 degrees but I accidentally ordered a continuous servo which means that the motor spins continuously and instead of controlling the angle of the motor, you control the speed of rotation. This is obviously not OK because I would not be able to move the finger reliably. However I realised that it was well suited to the motor driving the threaded rod.
I decided to make the whole thing out of wood and to use the laser cutter at uni to cut out all the pieces. There’s something about this construction technique that I really like.
Have you ever seen the “useless machine” robots that everyone makes. It’s just a box with a switch, and when you flick the switch, a robot arm pops out of the box and flicks it back – useless, hence the name.
Well I wanted to take it one step further.