Frame Design

Over the last few days, I've been having a go in Inventor and doing a mock-up of my designs. (I say mock-up as explained later.) This has helped solved some of the problems I've had and provoked ideas on what needs to be done and changed. None of the pictures have the x slide/axis carriage shown as that is a more detailed feature and so I haven't designed even a basic version yet for the design.

Temperature Sensor, Frame Design and News

Last post I said I would get my thermistor temperature sensor working by the next post (ie this one). I have it working but its not calibrated and thus gives the temperature a few degrees out.

Thermistor Calculations

So this post is more of a maths orientated post. It incorporates maths equations powered by mathjax and so needs a relatively modern browser to work. Mathjax is a tad slow to load as its hosted on their site as I can't add the code to Blogger.

So I've decided I would test out some thermistors that I had bought a while ago. I was looking round and found it hard to find a solid circuit diagram and I couldn't find any equation to get from the ADC value to the temperature. I eventually had the great idea of checking how the RAMPS circuit was done for the RepRap System.

Binary Buttons

This week I managed to get buttons working after lots of research for debouncing buttons. I went with hardware debouncing as was far easier to do. So this is a small circuit that takes input from four buttons and outputs them on a LCD as binary and decimal numbers. Here's a video of what I mean. My fingers are quite big compared to the PCB buttons so you can't really see me pressing the buttons.

Debugging, Buttons, new purchases

Sorry this post isn't going to have any pictures as its all ideas, or what I have done but not finished yet.

So yesterday I realised I hadn't actually done a project that involved buttons on the AVR. I had done so on the TI LaunchPad which I had used before I got the AVR hence why I thought I had done so (I only swapped 3 months ago). Due to this I have decided I'm going to make another test program which will take the state of four buttons and translate them into a 4 bit binary and display the decimal reading on an LCD screen. As I was getting my breadboard ready for the SPI test, I moved another AVR onto the same breadboard and downloaded the LCD code. Worked so I then started tidying up the code to make it more of a library rather than all in one file. I finally got the code to work (the statements for getting printf to work are quite hard to satisfy) and so downloaded to the AVR and the display did nothing. I thought it must be the code as it seemed to be working on the original chip on the board but not the second. So I spent the next hour trying to troubleshoot the code, eventually going back to the original code that I posted last time and it still didn't work. Eventually I found out that one of the crimped pins within the header plug on one end of the LCD cable had come loose and so the LCD wasn't actually receiving the data! Good lesson to remember - check the hardware first, don't assume its all ok, specially cables.