This Pit thread goes into some stuff that is frustrating Robot Arm’s attempt to make an NC Etch-a-Sketch. If other Dopers have an interest in this area I’d like to hear from them.
As I mention at the end of that thread I ordered a basic Arduino kit and I’d like to play around. Since my electronics bench is severely depleted of tools and parts I’ll probably start by making some kind of high functioning logic probe. I’d like it to measure voltage in addition to simple high-low indicators, and it should have an audio output because I love listening to capacitors discharge. A small display should have enough resolution to distinguish the waveform. It would be nice to have it measure resistance and current also.
Some of my plans (spoilered to conserve screen space on viewing):
I’m thinking about making a scope with it too. That would need a higher resolution display, something that could XY plot from analog inputs. In the old days I would have used my oscilloscope display to do something like that I think the solution now is to send the data back to the big computer for display.
Dr. Strangelove pointed out some low cost basic controllers that got me interested in an old idea. Putting together motion control machinery used to be a heavy duty task, matching up a lot of incompatible controllers, motors, and logic. I would have loved to have plug-and-play type components to work with. Like a rotary actuator that you just send commands to, like number of revolutions or degrees and a time component. Or linear actuators that just took a distance and time to move. And all of them could be sent messages to set the scale. So for these days each one would have a USB port and get chained together to be controlled from a single computer.
Anyway, there are some things like that out there now, but they’re expensive to be playing with. Some simple and inexpensive ways to do to this might move be along on my plan to start the robot rebellion.
This might be a decent learning experience, but it certainly isn’t cost-effective.
I’d concentrate on making a device that you can’t buy off-th shelf, and buying a Saelea instead.
I don’t think that the Arduino is going to be fast enough to make a decent logic probe or scope:
I think it will do to get started. If I need a scope or logic analyzer I’ll get one, but at the moment I’m just playing, and there’s the fun of doing it yourself. I want to see how readily these things can communicate through USB. Right now Arduino sounds very basic, from a reset you just kick off a simplistic loop. There are Arduinos with heftier CPUs and the Raspberry Pi out there also. So right now it’s a learning experience.
I bought one earlier this summer as a craft to do with my kids, and have sadly not been able to devote much time to it. Plans (in no certain order) are to make a Simon type game, and to use a hall sensor to make a bicycle speedometer.
I looked at a couple of Instructables for the Arduino. I’ll probably have a simple logic probe working in no time, giggle to myself while I use it on the Arduino board itself, and then hopefully I’ll find time do something else with it. Based on previous posts Robot Arm’s been working on his Etch-a-Sketch for a while, finding time for these things isn’t always easy.
One thing I may do is make a home hematocrit tester that I need. I’ll use a stepper motor as the centrifuge and work up something to compute the level from the length of the red section of the capillary tube. Pretty simple functionality, but I’ll feel so proud of myself for making it.
One project I’ve been procrastinating about is a small motorized programmable tripod head to take time lapse photos with a GoPro camera, the idea would be to have a small stepper motor panning the camera slowly as it takes photos over several minutes or hours.
It should be very simple to do, the mechanics would be 3D printed, but I haven’t had the time and other projects have gotten on the way.
I would 3D print the thing, maybe use a timing belt to increase the torque or just gears from an R/C helicopter for the same purpose.
Some years ago I built a computer controlled motorized panoramic tripod head for a DSLR camera and I used modified servo motors with a pinion gear attached to the output shaft driving a largish main rotor gear from an electric helicopter, it was enough to swing around a couple kilos worth of camera and lens.
Well, it took a little doing but I managed to clean up the damage inflicted by the various IDEs I tried using. I think.
So, I’ve got my drawing code separated into a class in a .h and a .cpp file. The only real way I’ve found to track what’s going on is to put in some code to output statements to the serial connection, and the Arduino editor can open a window that monitors that connection. That was helpful when I was getting the original version of the app to run. Once it’s running correctly, I can comment those statements out or even delete them. I’ve changed some of the logic in the new class, so I’m relying on that output again to see if the code is behaving the way it should.
Wow! Calls to the serial port are changing the values of variables. With the latest change, the whole flow of the program is different. As it runs now, a function call to print a text string to the serial port is outputting only some of the text, then the program returns to the beginning of the function containing that statement, and loops. According to the messages when I upload the sketch to the board, I shouldn’t be anywhere near the memory limits for code or variables.
I’ve dealt with weird bugs before, but I don’t know what the fuck is going on with this.
Just going to mention that. The symptoms sound like memory getting over-written. This is bringing back memories of ye olden days trying to cram code and data into 1K of memory, or less.
I toy with making some greenhouse controllers. There are already commercial solutions, but I think it would be fun.
Difficulty: My only programming experience is a class that taught me rudimentary C over 10 years ago. And I’ve never soldered anything. But sometimes learning by doing is the way to do it.
I have a real Saleae Logic and one of the clones, and they function identically. The inside is just a CY7C68013A microcontroller and very little else. It doesn’t even store its own firmware, nor have any authentication, so it works with the Saleae software.
Obviously I think people should buy the legit device, but I got a clone for the same reason I (back when I still used spinny discs) ripped any CD I owned and kept the copy in my car. If it broke, got stolen, or whatever, I still have the original.
Finally made a video of the semi-finished version of my flipdot project. Check it out.
The display is from here, and I use an Arduino with Bluetooth serial port to interface with it. My phone ultimately controls it. Some more details here.
I think the solution now is to send the data back to the big computer for display.