Stefano<p>Part 3 of building the DIY seismograph. So continuing on the moving arm concept, I settled on using a servo motor as this could easily be driven by the Arduino. I had to make the arm very light so as not to put too much pressure on the small servo motor I was going to use. Here is the model of the arm. Although I went back and forth with different ends to hold the pen, ultimately I ended up going with this clip. Modeled in <a href="https://mstdn.ca/tags/freecad" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>freecad</span></a> <a href="https://mstdn.ca/tags/maker" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>maker</span></a> <a href="https://mstdn.ca/tags/diy" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>diy</span></a> <a href="https://mstdn.ca/tags/earthquake" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>earthquake</span></a> <a href="https://mstdn.ca/tags/arduino" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>arduino</span></a> <a href="https://mstdn.ca/tags/servomotor" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>servomotor</span></a> <a href="https://mstdn.ca/tags/seismograph" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>seismograph</span></a></p>