Galvanometers Homework
Hello,
Before cotinuing with this project we should first fully understand what are we about to build. What is a Galvanometer?
First lets start with Wikipedia that has the following information about modern galvos: “Galvanometer mechanisms are divided into moving magnet and moving coil galvanometers; in addition, they are divided into closed-loop and open-loop - or resonant - types”. So we know we are going to build a moving magnet galvo, what about this loop thing? Well this is better explained by ChaN.
Graph of Galvos response given by ChaN
So “open-loop galvo’s shaft is held with a torsion-rod spring” this means that the shaft will swing back and forth to find a stable position because of the spring this makes the shaft reach its destiny much later and wastes more energy with the resonance.
Closed-loop galvos relay on the feed back to be aware of the current position not needing the spring mechanism for stabilization but require more sensing electronics to control it.
Now we know we are building a magnet moving closed-loop galvanometer. Lets see what is available from a couple of commercial sources and their characteristics:
They are super fast and super expensive!!! So acquiring galvanometers from such companies would be a direct NO for me just because of the price. Let’s see how far we can get with our DIY galvos.
We can notice that they usually are cylindrical instead of parallelepiped like ChaN’s and the one we are building so I am wondering how they distribute the coil inside. I found this web site with some explanations and pictures but noting indicating how they use a cylindrical coil.
The magnets that I ordered are bigger than I expected so I think it will be hard to get a smaller galvo than ChaN’s.
Something that I will probably have to change before the next iteration is the shaft material so something more rigid like ChaN’s since the rod I have has some flexibility that can give us some oscillation, but lets test it like this for now and see the results since the space where the rod can oscillate will be very limited.
I’ll start printing some galvo cases to start assembling the first prototypes and I will post the 3D models here soon.
