Basic Pulse Wheel

thingiverse

Going a mite bit more complex this week... This is a basic pulse wheel for DIY projects. These little guys are commonly used in electronics to detect the velocity and direction of rotational motion without inserting drag or friction into the system, like a roller detector would cause. You simply shine an LED, laser or other light source through the slits on one side of the wheel and detect it with a photosensor on the other side, then send the pulses to whatever you need to do detection and analysis. You can even detect direction of rotation by using two detection sensors and comparing their outputs. This is exactly how old school trackball mice did their magic, and the method is still widely used today in a myriad of machines of all kinds. The disc diameter is 30mm, the slits are 1mm wide, the center hole is 3.2mm, and the disc thickness is 3mm. I made the center hole 3.2mm to compensate for print inflation. In practice, printed in PETG, this thing spins very nicely on a #4 machine screw, although it could be tightened down a bit to cut down on wobble. Print Settings Printer Brand: Robo 3D Printer: R1 ABS + PLA Model Rafts: No Supports: No Resolution: Whatever you like. Infill: Doesn't really matter, it's the outside surfaces that count. Notes: Print it flat to the bed and it should behave nicely without support of any kind. You can use whatever plastic you prefer, although I like the low friction and high durability properties of PETG. The outer edge is ribbed to provide a small amount of friction if needed, so it can in fact be used as a friction roller detector as well as a shaft rotation type detector. One thing to note: This object can be a little challenging to print due to the 1mm slits. If you can pull this one off without a hitch, you've got yourself a good setup going. It will test bed adhesion and print resolution quite thoroughly. If you find that the slits are wanting to close up during printing, then try slowing down the print speed, reducing the print temperature, and reducing the extrusion multiplier until it comes out right. If using a sissy plastic like PLA, be careful about bed temperatures lest that base layer try to sag and expand too much. Reduce the bed heat until base layer expansion is minimal, yet the layer still adheres. All of these factors are important to get your head around in general anyway, because they will affect the print quality on everything you try to make. Consider this piece to be good practice for honing your abilities. IMPORTANT NOTE: Yes, I did just refer to PLA as a "sissy plastic," lol. If you're a PLA fan, please don't be insulted, I just don't really like the stuff anymore. Everyone needs to find their own way with these incessantly nitpicky machines, and if you're comfortable with PLA or you even love it to death, then good for you and you should be totally contented with your choice. I don't like it because of its low glass transition temp and other little personality quirks, but that's just my preference. I always recommend exploring other options in order to expand your horizons, but I don't believe in being forceful about it.