Velko's builds

Earlier I worked on a display module, but could not proceed because I had no means of programming an EEPROM. I had to step aside for a moment and build a device that can do that. Now I have programmer, but what data should I write on the chip? Well, Ben explained the main idea quite carefully in a series of videos, but my build differs a little. One thing is - I did not follow the videos exactly, so I'm fairly certain that I have connected display segments to EEPROM's data output pins differently. In Ben's video there were several wires, connecting pins on different sides of EEPROM and displays. I have just one. Ben mapped every digit on a paper and carefully worked out the byte values for each. I suppose it's fine if you want to show the process in detail. But I have lazier idea - let C compiler and Arduino do it for me. They are much better at performing tedious calculations. I'll just set the rules. For starters, I have to figure out which bit is connected to w...

In previous post I got to the point where I need to program an EEPROM, but have no device to do that. This time I'll try to build it. Ben had similar side-build as part of his Output register , so this should be a replica of that, right? Well it could have been, but I did not follow his footsteps exactly. First, I do not have Arduino Micro , just an Uno with a half-size breadboard attached to it. So I was planning to use that. I could not source 74HC595 shift registers, so I got 74HC594 instead. As it turned out later, they are so similar, that there actually are no differences for this use-case, but I did not compare them carefully at the beginning. Also, I was not following the video exactly, just got the main idea about shift registers and continued on my own. Placed the chips on the small breadboard, but there was a problem - the breadboard was a little too short. I placed chips end-to-end without any gaps in between, and there was just enough holes to fit all the pins. Unfort...

In his series , after building the clock module, Ben started to work on registers . Those are important parts of the computer, but feels a little underwhelming again. So I decided to go for output display instead. The module requires a clock for multiplexing its output to four 7-segment displays. The clock should eventually be independent from the main clock and run much faster. But in the meantime other parts of the computer do not exist yet, and I might like to run it really slow. So I just placed the 555 on the board, but did not even bothered to wire it up. I'll just use signal from my freshly finished clock module . I haven't really used it for anything yet! Ben used 74LS76 JK flip-flop to manually build a 2 bit counter. I just went for 74HC163. It's a 4-bit counter, but there's no harm in using only two outputs. Wired counter to inputs of (one side of) 74HC139 2-to-4 demultiplexer - that should allow us to cycle the displays. I was anxious to see if I'm on the...

The parts are finally here an I can have some fun! Since nothing runs without clock, I decided to start with that module. It's probably not the most fun one, but I definitely need it, before doing something else. I was planning to follow Ben's design to some point. I had some TS555CN timers at home, so I decided to try those first, before opening the package with the new ones I ordered. Wired up the 555 in basic astable configuration with capacitors, potentiometer and decided to test if it works. So I connected a LED to the output and powered it up. It worked. Well, sort of. LED blinked and I  could adjust the frequency, but then suddenly it started to blink very fast, then again back to normal. What's even stranger I could trigger or suppress the effect by touching either chip or capacitor (just top of the chip, not the leads). I did accidentally connect my power backwards on first try 😓, so I figured it caused some damage or something. Replaced the chip with one of my n...

In order to start building, I need some materials and parts, I have to order those first. In terms of logic chips I decided to go with 74HC* series (Ben used 74LS* in his builds). Why? Well, it looks like it's newer design with lower power consumption, also the list of what's currently is stock looks better. I won't be able to mix the logic families trough, there are some differences on what voltages are considered LOW and HIGH between them.