This week was less productive because of Winter Carnival. I found information and electrical schematics in older documentation (here). The reason there are two stepper drivers is because one is used for simulating the input from the printer. It does not need to be included in the actual assembly.
This week I plan to do the following:
- Design a PCB from the schematics to determine the required size of PCB. This will help the mechanical design.
- I am not completely sure what else I will do this week. Our team meeting was interrupted by Winter Carnival last week.
This week I worked on creating a circuit diagram for our circuit using Fusion 360. I downloaded the layout of the Pololu DRV8825 Carrier that we are using from here and the Arduino Nano from here. As I was creating the diagram, I became less confident that these are the correct models (the pins don’t make sense) and I may have to create the layout myself. The current iteration of the diagram is below. I have not yet connected everything together because the proportions of the stepper drivers and the Arduino Nano seemed wrong. The stepper drivers should be significantly smaller than the Arduino Nano.
This week I plan to work on the following:
- Ensure all components and schematics are accurate.
- Fix or remodel any that are not.
- Connect the schematic together.
- Add the hall effect sensor into the model.
- Start designing a PCB so that we can also begin designing the hardware to hold it.
This week I have reacquainted myself with the project as well as learning more about the electrical layout of the project. I am trying to figure out why two motor controllers are on the breadboard when we are only using one motor.
We have discussed a few possibilities to help resolve the noise problem. One possible issue is a mismatch in the sensitivity of the sensor and the arduino. They may have different increments meaning that sometimes an increment from the sensor will be “skipped” by the arduino. According to its datasheet, the sensor has a typical sensitivity of 3.125 mV/Gauss. We think the arduino has a sensitivity of 4.883 mV (5V/1024 increments), but we aren’t completely sure yet. Because the sensitivities are not quite matched, the difference adds up over time. This is demonstrated in the graph below. One potential solution is using an amplifier to increase the signal strength of the sensor so that every time a value is “skipped” it is less significant. This is also shown below. I used 10x amplification to illustrate the point. We will probably not use that much.
I envision the project to look something like this by the end of the semester:
The dimensions are not quite how I imagine them – I’m not an artist, but the idea is still there.
Next week I plan to do the following:
- Create an electrical schematic of the project.
- I will design a PCB to connect everything when the design is more finalized.
- Look into if using an amplifier will work (voltage range of arduino and sensor) and alternative methods to accomplish the same idea.
- Identify voltage range the arduino can handle.
- Identify maximum safe amplification.
- Look into alternative options.
- If everything looks okay, then design an op-amp circuit for the correct amplification.
- Identify voltage range the arduino can handle.
10/28/23 – 11/4/23
I have decided to use this holder to attach the arduino nano to the sensor, at least for now. I don’t love its position very much, but it’s the best place I could find.
Next week I will begin 3D printing it so that we can continue to a more integrated test.
10/21/23 – 10/28
This week I have been working more on the mounting mechanism (pictures below). The problem that has taken up most of my time has been trying to add holes for mounting. I imported the sensor block as an STL file, so the software doesn’t consider it an “object.” This makes removing material from it much harder. I have a few ideas to work around this if I cannot find a solution soon.
- Add a “holder” onto the design, making it more complex and bulky.
- Add material to where the holes should go as a guide to make the holes with other tools after printing. This risks breaking it in other ways though.
- Remake the entire sensor body in my CAD software so that I can have the part file required to add the holes to it. I am not inclined to take this route as it will take much longer than the others.
9/30/23 – 10/7/23
I have been working on a way to mount the sensor and other electronics to the 3D printer. My plan is to modify the sensor housing. I will add mounting holes for the electronics. I also plan to attach it to the “idler” by printing a new part with both combined into one. Most of my time this week has been spent learning to use FreeCAD.
9/17/23 – 9/23/23
Researched the power source specifications and extruder wiring diagrams of the Lulzbot Taz 6 to determine where we can tap power from and how to intercept the signal from the extruder stepper.
The power can come directly from the power source as it is 24V, which is what we are using for our electronics.
The extruder pin-out was found from the open source documentation here. Intercepting at this connector seems easiest because we can take the motor pins and let all other signals pass. We can then send our new signal directly to the motor. From a wiring diagram and a BOM I found the connector housing used in the 3D printer. The wires appear to be 22 awg, so they would use a female connector like this and a male connector like this.