1. 6 GHz frequency modulated radar

Making a cheap and simple radar with a range of about 100 meters.

2. Making embedded Linux computer

Designing and soldering a small ARM Linux board with 217 ball BGA package and 0402 passive components

3. BSDL file to KiCad library converter

I made a small tool to automatically convert a BSDL file to KiCad library.

4. Simulating audio effects with SPICE

While I was looking at some audio effect circuit schematics at the internet, I though that it would be nice to try to simulate them SPICE first and listen them, before building them to confirm if they sound good or not ...

5. Toaster oven reflow controller

Nowadays many of the most "exiting" chips come only in leadless packages, such as BGA and QFN which are hard or impossible to solder just by soldering iron, because leads are under the chip where they can't be reached. These kinds of chips are usually soldered using reflow soldering ...

6. I made a Geiger counter

Ionizing radiation is something that almost anyone finds exciting (or scary) and I've also been for long wanted to build a Geiger counter. Unfortunately Geiger tubes have usually been too expensive to seriously consider buying them just for a hobby project. But I found out that sovtube sold soviet ...

7. Fast brainfuck microprocessor

Brainfuck is a minimalist programming language. It's mostly a toy and writing any real programs with it is almost impossible. Its design is very simple, the whole language has only eight valid instructions which operate on an array of bytes initialized to zero. Data on the array is manipulated ...

8. Datapath of my PIC16F84 microprocessor clone

PIC16F84 is old 8-bit microprocessor made by Microchip. It was once very popular among the hobbyists, because of its low price. It was the first microprocessor I started to use so I thought it would be fun to try remaking it in VHDL. The source code is open source and ...

9. Quaternion roots of modern vector calculus

Before the vector calculus was invented mathematicians used to do vector calculus like operations using quaternions. Quaternions are four dimensional extension of complex numbers. They have two additional imaginary units $j$ and $k$. Quaternion multiplication is non-commutative and is defined by the formula:

i^2=j^2=k^2=ijk ...

10. UART designed to be used with FSM

Some time ago I needed an UART for a project. Things it needed to do were very simple and I didn't want to add a microprocessor to use UART and instead decided to just code a simple finite state machine to use it.

But I couldn't find a ...

11. Generating normally distributed pseudorandom numbers on a FPGA

The other day I was coding an FPGA design that needed a source of normally distributed random numbers. Uniformly distributed random numbers are fairly easy and cheap to generate with a linear feedback shift register, but generating normally distributed numbers is a harder problem. There are several ways to generate ...

12. Progress on evolutionary circuits

If you haven't been reading my last entries, I have been working on a program that tries to design a circuits using genetic algorithm that fulfill the requirements given by the programmer. Read this entry for an overview what the program does and how it works. In this post ...

13. In-place sparse matrix conversion algorithm

I have been writing a sparse matrix library for few weeks and for it I needed a algorithm for converting from coordinate list form(COO) matrix to compressed sparse column form(CSC). All of the algorithms that I found allocated space for the CSC matrix and freed the COO matrix ...

14. Better evolved BJT inverter

In my first post about my evolutionary circuits project I wrote about an evolved BJT inverter. I have since that post written some new features in the program. Now it can measure the current taken from logic input and the power supply, so the last best solution where the transistors ...

15. Metastable transistor circuit

In my previous post I wrote about a circuit that would change it's output depending on what was the spice simulations DC sweep range. Today I investigated the circuit a little and I was able to remove lots of components that didn't affect the bug and this is ...

16. Building an evolved voltage reference

I've been playing with the electronic circuit genetic algorithm design program. I have tried to make some stable bandgap voltage references, so far results have been promising, but not very good. None of the resulting circuits could be used in a production, except if you don't care much ...

17. Evolutionary algorithms and analog electronic circuits

I've been working for a while on a program that automatically generates analog electronic circuits using evolutionary algorithms. It's still very much a work in progress, but I've used it to generate some useful circuits. Current workings of the program is as follows:

1. Programmer decides a goal ...
18. Remembering derivatives of sin x and cos x

I was never good with remembering if derivate of $\sin x$ was plus or minus $\cos x$. Or if the derivative of $\cos x$ was plus or minus $\sin x$. I could just remember that one derivative had minus and other didn't. But I don't have that problem ...

19. Redefining the number 2 in Python

In Python it's possible to redefine some builtin values that shouldn't really be changed. For example True and False can be changed in Python versions 2.7 and lower. This is fixed in Python 3 and assignment to True or False raises: "SyntaxError: assigment to keyword" but it ...

20. Approximating the cutoff frequency of a filter

A long time ago I read from some book, probably some of the Jim William's or Bob Pease's books, interesting trick to approximate the cutoff frequency of a simple low or high pass filter. Below is equation for the cutoff frequency of a first order low or high ...