Reddit:Electronics

Hey folks!
I’ve been playing around with the rosco m68k open-source computer lately and wanted to share some progress.
I’m working on this as part of my personal project SolderDemon, where I’ve been experimenting with DIY retro-computing hardware.

On my boards the official firmware boots cleanly, the memory checks pass, and UART I/O behaves exactly as it should. I’m using the official rosco tools to verify RAM/ROM mapping, decoding, and the overall bring-up process. I also managed to get a small “hello world” running over serial after sorting out the toolchain with their Docker setup.

I’m also tinkering with a 6502 through-hole version — something simple for hands-on exploration of that architecture.

Happy to answer any questions or discuss the bring-up process.

My first Smart Socket :)

Low-Power

https://github.com/UDFSoft/UdfSmartSocket

yet still one pair leads to nonexisting chip and second shows only diagnostics from mcu. Life is brutal.

I had a free evening, so decided to make this in the shed/workshop.

It uses a 555 to produce rapid pulses, and a 4017 decade counter to sequence 6 LEDs rapidly.
Pressing the button pulls current through an opto-isolator, whos phototransistor connects pin 3 of the 555 to the trigger of the 4017.
A small capacitor was placed across the contacts of the push button, so that the dice continues to 'roll' for a second or two after releasing the button (Makes sure that people can't rapidly release and re-press for a more preferable number.

in r/askelectronics I asked for advice about more chips I can use in the future, and got another 4000 series which will allow me to drive a seven segment display in the same fashion, as opposed to six individual LEDs.

Once I was happy with how the circuit behaves on the breadboard I put it to stripboard.
From what I have seen, most people here seem to use the perfboard, which has pads which are disconnected from each other.
I personally prefer stripboard, as it's what I've grown up with as a kid. You can use a drill shaped tool to cut the copper tracks where needed.

I decided to current limit the white LEDs with a 12KR resistor.
I had one to hand, and it dims them down to the same brightness as a standard diffused red, yellow or green variant.

I don't know if using an opto-isolator in the way I did is good practice or not. It works, and is simple enough.
I don't really have any official teachings in electronics, so sometimes I have a different approach to a problem.
Sometimes for the better, sometimes not.

I found that for me, the best way to use a pulldown resistor for the 4017 trigger was to also connect a small .1uF ceramic capacitor in parallel to the pulldown resistor.

I know that by no means is this groundbreaking, or advanced. It's probably akin to something that would have been made 30 or 40 years ago, but I only dabble as a hobby, and find soldering away, alone, for a few hours, whilst the rain hammers down outside quite therapeutic for me.

So, I'm developing a guitar amplifier for a friend, and I need a high power (as for my standards) amp to make it loud. So I made this one, the most powerful discrete amp to date, that can deliver 20Vpp to 8 ohm speaker without distortion at 24V supply. I had a problem with connecting everything for tests and idle current calibration because PCB is , so i had to improvise. I put a power diode into ground terminal of amp, connected a big clip of function generator ground, then connecred small clip of power supply ground, and scope ground to power supplu ground clip. The effect is this big tangle of wires and connectors, but it worked as intended. The design is a variation of amp from 70s record player but with changed voltage rating and conversion from class B to AB. It's suprisingly stable and silent when input is floating, so I like it.

Can't run down to RS anymore

I wanted to get started with FPGAs by making my own development board, and thus I made Arctyx Nano!

https://github.com/Keyaan-07/Arctyx-Nano - everything is open-sourced under MIT License!

Arctyx Nano is a low-cost, open source FPGA development board carrying the ICE40-UP5K FPGA from lattice along with the RP2350A in a raspberry pi pico form factor. It consists of 6 LEDs and one RGB LED. All the pins on both the ICs are used in one way or another.

I am currently using APIO open-source toolchain to verify, simulate and build projects and to upload using APIO, i have to figure it out.

This is my first FPGA PCB and i would love feedback on my design!

This board was created as a project for hackclub blueprint, check it out!!

We used the following circuit elements for measurement trials:
Diodes: 1N4148, 1N4004, 1N270
Transistors: BC237, BC547, 2SC3355
Circuit elements: 22 microfarad capacitor, 3.3 K resistor

Still working on the matrix mapping but it does work besides a few toasted keys. Planning to work on some chord progression/arpeggiator code and connect it to a Korg DS8 of the same era.

Diseñé y simulé una ALU de 16 bits en Proteus, capaz de ejecutar operaciones AND, OR, XOR, SUMA y RESTA (con acarreo). Todo está organizado en módulos para facilitar el análisis, e incluye flags e indicadores para validar el comportamiento de cada operación.

Si desean obtener el archivo de simulación, pueden escribirme directamente.

Turning led on slowly

Used a 5V regulator, 2 buttons and 2 NPN transistors to control the shared segment.

I am still learning, this was my first attempt at trying a project without copying a YouTube tutorial.

Zener voltage = 5.1 V, Input voltage = 9 V, Resistance = 500 ohm

Late 90s before Ethernet control was anywhere near affordable and circuit control over the Internet was sci-fi dreams here was a $20 external HP JetDirect print sever controlling 8 GPIOs with Opto22 SSRs and a little fool logic to make the print sever think its connected to a real printer lol the NAND gate fooled the JetDirect that every time a byte was "sent to the printer" the printer flapped strobe as if it has printed the bye :) Data was piped via good old Linux NetCat - wait using Linux in the 90s...oh I'm getting emotional already

I’ve so forgotten those days of badass innovation - now smart plugs are everywhere …