2021. január 31., vasárnap

Hi-Fi Rack - Motorized turntable tray 3.

This year I decided, to complete some previously abandoned projects of mine. I'd like to finish one of those in every month. It is just a plan and not a promise (I don't want to fell into the trap of unkept new year's resolutions).

The first one in the row (for January) is my motorized turntable tray. The previous posts about it can be seen here:

Since I restarted January, many things happened with it:

  • Added the final electronics
  • Changed the TI DRV8825 stepper driver to Trinamic TMC2209
  • Almost completely rewritten the code, based on TMCDriver and AccelStepper, while keeping the original touch sensor library.
  • There was an achievement from my side, that after a long struggling period, my 3D printer is back online and working stable, so I was able to add 3D printed parts. This way a new cable management arm come into picture instead of the unreliable tape used previously. It is used for the touch sensor cable and the mains cable. For the audio cable I may create a second arm sometime.
  • I also 3D printed the holder for the connector at the back panel.
  • Created a kind of power breakout box (temporary solution until the proper supply is made):
    It has:
    • +12V - Wall Wart adapter for a time being
    • +5V  - Wall Wart adapter for a time being
    • Earthing (for the touch sensor)
    • Serial connection
  • Mounted it into it's final place

While I was writing the serial communication part of the code (it will be used later), a weird issue raised.

The connection to the PC just created unusable data stream. A complete mess. Even I changed the USB-Serial adapter. I didn't understood why. Then an idea pop into my mind, and...

Yes, I used a 12MHz crystal instead of 16MHz. This means, everything working correctly, except the serial communication. When I used 115200 on the arduino side and 86400 on the terminal side, the communication eventually started to work normally.
I didn't wanted to keep it this way, so changed:

The complete electronics, in it's place with the motor and the cable management arm

The power breakout box

Now only a few things left to do:

  • A better GT2 pulley mount
  • A second cable management arm for the audio cable
  • The next phase of the project, what will contain the proper power supply also
Working on my desk:

Project finished, mounted into it's final place:

The design and the code reside here:

2021. január 22., péntek

Fake in China (EPROMs)

 When I opened the HP 8903B Audio Analyzer I realized, that the rom memory on the processor board is assembled from various chips from various providers, what I not really like. The EPROMs anyway need reprogramming after a few decades, to keep the instrument working in stability.

As I didn't want to erase the originals, I had the plan to create a complete new EPROM set. The 2716 and 2516 EPROMs are not available anymore from any of the regular suppliers. So I went to the eBay to find some. Ordered 20pcs. Arrived from China:

I know, that the manufacturers time to time change the process of the devices kept on the market. But come one! Three different chip size, with the same date code?

Guys, you can do better job than this! :-D

Anyway, I tried. One out of the twenty acted like an EPROM in the programmer, even this one was failing during the programming cycle.