3D Printer update

I’ve finally started getting back into printing. I had a bunch of filament feed issues, and it was a combination of a loose hobbed gear, and the set screw part of one of the extruder drive gears started to fail. Fortunately, I had enough stability left to print a few spares (in addition to the 4 I had in reserve, just in case). I got everything going again, printed a few things, and was printing during the scope repair. Then this: This was a new failure mode, but not completely unexpected. I’m not certain if it was just a bad gear, or if the Skin plugin I was experimenting with was causing the gear to be loaded more than usual. The automatic extruder fan seems to be working though. I’ll video it next time I have the printer repaired.  

Read more

New Oscilliscope Part 2 – Repair

Continuing work on the TDS544A, I got all of the electrolytic capacitors off, and cleaned the board with simple green and alcohol. I took careful notes about what value of capacitor went where, and how all of the cables are hooked up internally. I also noted any switch settings I could find. The Digikey order of capacitors and a brand new ultra fine tip for my iron arrived.Here we are mid process on getting all the capacitors back on. It turns out I did not order enough of the 33µF capacitors, so I ended up substituting the 10µF capacitors in some places on the logic board, and on the front panel. The Acquisition board got all the proper values, since it might be important for the RAM and other major signal processing elements. On the logic board, I replaced about half of the capacitors on the power rails with the […]

Read more

New Oscilliscope Part 1 – Disassembly

We were cleaning out the lab at work, and throwing out older lab equipment, and I scored a Tektronix TDS 544A. The sticker indicated it needed to be repaired and calibrated, and it just wasn’t going to be worth it, so they were tossing it. I scooped it up, and I’ll have a few blog posts about the repair process. First, the good – It’s a 4 channel 500MHz digitizing scope with a color CRT screen. It beats the heck out of my older TEK T935A, which is an analog 2CH 35MHz scope. I think the biggest win is the ability to stop the scope and look at a trace, as well as much more powerful triggering options. Powering it on, it has a few faults in the self diagnostics, and research online shows that the main problem with scopes from this era are the aluminum electrolytic capacitors on the main […]

Read more

Extruder fan controller

I brought my makerbot to the Reading Friends and Family Day to show at the Reading Robockets booth. I’ve been having some issues with the extruder skipping, and I think part of the problem is that the stepper motor that does the extrusion is overheating a little. MIT Swapfest was also this past weekend, and I got a number of small useful items, like a few of these fans for $1 each (including the finger guard). these fans are LOUD and move a lot of air.   One thing that I liked about the fans is that they are the four wire variety which means they can have speed controlled with a PWM signal applied to the blue wire. The base frequency is around 25 kHz, and the duty cycle controls speed (from 30% to 100%). I did a bit of research online, and came across a neat ieda for […]

Read more

Hello again, world!

Whelp, I managed to drop my entire database while working on some web development…. The automatic backup didn’t work, and I have nothing to restore. I managed to get my blog content out of google’s cache, but it will take some effort to turn it back into blog posts, so this will be empty for a while….

Read more

PID explained

The topic of PID often comes up when I talk with FIRST teams. This post is how I explain it to students. I was recently explaining it in a post on Chief Delphi, so I decided to turn it into a blog post while I was at it. The basic idea for PID is that it corrects for errors. if you make a PID loop based on position, it will move your motors such that the position is what you want. you can replace the word position with the words velocity, angle, and even acceleration or motor current. you can also loop multiple parts of your motion. (i.e. Loop position and velocity), but for FIRST, you usually only need to put a loop around one thing. Let’s use position for discussion, which is easiest to visualize. First, you need a way to measure your position (an encoder can be used […]

Read more
1 2 3 4