Blog - Sketching with Hardware


Published on: | Author: Alexander Heinrich | Categories: 2014b, Projects




SneakyPaint is a robot vandal. It is built for a disruption of social space. It does this by leaving a paint trail behind and laughing at you afterwards. Until it switches into operation mode, it is cleverly disguised as a bucket of paint, seemingly left behind by a careless painter.



As a starting point we had a remote controlled car, which we were supposed to transform into our robot. We quickly discovered that the motor was not sufficiently powerful enough to carry a weight higher than 650 grams, so we had already found a first hurdle. Instead of trying to address this immediately, we decided to focus on our spraying mechanism.

Our main goal was to find a way to transform the rotation movement of a servo, so that it would press down the head of a spray can. Luckily there exists a clip-on device for spray cans, which solved this problem very well. All that had to be done was to make frame for servo to hold it in place.


The second step was to get a paint bucket, in order to use it as a chassis and mount it on the frame of the car. We then installed the spray contraption in the bucket.


Now the problem of weight and sufficient power for all components, which we had discovered on the first day, was coming back to haunt us. It turns out that on a normal one battery setup our robot was unable to move an inch. The answer to this was: More power! We first thought of increasing the voltage of our circuit or replacing the provided with our own more suited ones. Our battery of choice was a 12.5 V Lithium rechargeable. However, due to the high risk of injury at over- or undercharge, our supervisors recommended a different, more simple solution: Parallel battery input. This way it was possible to increase the ampere enough to give our motor sufficient power to move our robot without increasing the voltage.


The rest was software.


The robot was designed with the intention of vandalism, so a pattern had to be programmed that it would spray on the ground after a certain time. The pattern of choice for us was a spiral that switched the direction midway through. An “8” as it were.

Since we decided we didn’t need any sensors for our concept, our robot had no guidance and it could only work with its internal clock as an indirect measure of distance. This method proved itself to be simple but very effective.

As an alternative way of operation, we mapped some of internal functions to serial prompts, that it would be sent via a bluetooth connection. This worked in test runs, although we did not have enough time to implement an application to control our robot.

The cause of this was that because of our increased power, the components were a lot more likely to break down. All in all 3 servos and motor broke down. Luckily, due to frequent trips to Conrad electronics store we could replace all of the parts in time for our presentation.



Final result:

We have successfully constructed a robot, which can potentially paint any shape the user designs and programs. It can be extended with sensors, in order to be more aware of its environment and avoid any obstacles, that might be in the way.

Apart from this, we were quite surprised, that we met all of our goals, that we had set on day 1 and that our robot reliably was able to paint the shapes, that we wanted it to.

Sneaky Video!

linked categories 2014b, Projects


Write a comment