Hello,
First time post here.
I have a project where I want to log the force vs displacement of various non-linear springs.
I’m using an ‘Infiduino UNO’, with a load cell for measuring the force, and a set of digital calipers for measuring the displacement.
I want to log the recorded values to a SD card, so that I can later view/manipulate the data.
I also would like to plot the data in real time on a small display (I have a 3.5” tft shield).
The load cell is working well. I’m using a HX711 to interface it with the Arduino. No problems with that part of the project.
The HX711 will use up two inputs (clock & data).
Interfacing with the digital calipers is proving to be a challenge, but I’m making progress there, and expect to eventually sort out my code (I’ll post my specific issues with the caliper interface in a separate thread).
If I can’t get the digital caliper interface to work, I’ll revert to using a linear potentiometer into the arduino’s analog inputs.
The digital caliper interface will use up another two inputs (clock & data), or a linear pot would use one input.
For the data logging, I have a SD card shield (with RTC included). I have previously had success with this shield on another simple project (logging my dog barking when I’m not home).
The digital calipers send out a signal approximately every 0.3s, which is a sufficient sample rate for my project. So for every measurement that the calipers spit out, I plan to log that, as well as the load cell value, and a time stamp from the RTC.
To plot the data on the TFT display, I would just use the Force/Displacement data to draw a white pixel at every sample.
The 3.5” TFT display also has a mini SD card slot in the back, so potentially I can use that for data logging rather than the separate logging shield. The only drawback would be that I wouldn’t have a proper time-stamp from the RTC, which isn’t really a deal-breaker, I can manage with a micros() time stamp. Or I could add a separate RTC to the circuit.
So, my major challenge is now how to combine all of this onto one Arduino.
The 3.5” TFT appears to use most of the available pins. I could discard some of the input pins, since I’m not interested in using the ‘touch screen’ aspect of it. But I don’t think this will free up enough pins required by the other components.
Could I run all of these devices on one ‘loop’ using the I2C protocol? I’ve since bought a small I2C display, but it is really a bit too small for my liking.
I would appreciate any suggestions regarding the best way to combine all of this with a single UNO board (I have ordered a MEGA also, in case that will make things easier).
My code will run something like this:
Wait for calipers to send out data, interpret caliper data, read load cell, write caliper & load cell & time stamp to SD card, draw caliper & load cell pixel on display, repeat.
Thanks,
Hugh.
