Learning the Art of Electronics, Week 1

Week 1. Ohms law, power, Kirchhoff`s law V,I. Ohm`s law V=IR. So what is a Volt ? Potential energy per unit charge or work done to move a charge against electric field, form one potential to a higher potential. Dynamic resistance Rdynamic= ΔV/ΔI it is the local resistance - the tangent to the slope of the device V-I curve. Power P=I×V or derived: P=I²R or P=V²/R Kirchhoff`s law: sum of voltages around circuit is zero, sum of currents in and out of node is zero. Parallel resistance: Rtotal = (R1×R2)/(R1+R2) Rule of thumb: if two parallel resistors differ by a factor of ten or more, then we can ignore the larger of two. In other words: in a parallel circuit, resistor much smaller than other dominates. Ina series circuits, the larger resistor dominates. Voltage divider. Rely on fact the I is the same on top and bottom. Vout = Vin × R2 / (R1+R2) Tip: since the current at the top and bottom are equal, the voltage drops are proportional to the resistances. So if the lower leg is ten times the upper leg, it will show 90% of the input voltage ( or 10/11 if exactly). Or if…

0 Comments

Learning the Art Of Electronics

I have decided to get my self together and systematize my knowledge of electronics. It is very similar situation as for this guy. Electronics is my hobby. And actually one of many hobbies. I would say I have a lot of knowledge it but there are plenty of gaps and places just for intuition. Especially in circuit design. Once I have purchased a book "Learning The art Of Electronics" and used it as reference for this and that but never when through it. But this is it. My goal is to complete one lab at least once a week and post a report here. Hopefully I will make it through :)  

0 Comments

Materialized view support in different DBMS

Some notes regarding materialized view support in different database management systems. Materialized view is a database object that stores a snapshot of database query. If a regular database view could be seen as a "window" - one looks through this window and sees actual situation of the data, then "materialized view " would be something like a "photo image" i.e., you take an image and can look at it even without going near window, but you only see situation that was on that particular moment picture was taken and if you want to update - you have to take another picture etc. Different DBMS have different materialized view implementation, lets go thorough most popular ones and look how they are supported. Oracle Wikipedia states that oracle was first to implement materialized view in version 8i. CREATE MATERIALIZED VIEW MV_MY_VIEW REFRESH FAST START WITH SYSDATE NEXT SYSDATE + 1 AS SELECT * FROM <table_name>; PostgreSQL PostgreSQL supports materialized view from version 9.3 CREATE MATERIALIZED VIEW MV_MY_VIEW [ WITH ( storage_parameter [= value] [, ... ] ) ] [ TABLESPACE tablespace_name ] AS SELECT * FROM <table_name>; SQL Server SQL server has different concept and it is called Indexed View. The…

0 Comments

Reliacinė algebra ir norminės formos

Kai kurie žymėjimai ir reliacinė algebra R={A1,A2,...,An} t.y, R yra lentelės L atributų aibė. Ai kur i=1,...,n yra lentelės atributas. Tada L(R) yra lentelės reliacinė schema. Lentelės eilučių aibę žymima l={e1,e2,...,em} kur n - lentelės stulpelių skaičius, m - lentelės eilučių skaičius. Kiekviena eilutė yra sutvarkytas reikšmių rinkinys ej = <a1,a2,...,an> ∈ l; ai ∈ dom(Ai), kur dom(Ai) yra atributo Ai domenas t.y, galimų reikšmių aibė. i=1,...,n j=1,...,m Atributų rinkinys apibūdinantis bet kurią lentelės eilutę yra vadinamas viršrakčiu. Viršraktis yra raktas jei pašalinus bent vieną atributą jis praranda universalumą. Taigi raktas yra minimali atributų aibė, vienareikšmiškai apibrėžianti visų atributų reikšmes kiekvienoje eilutėje. Jei raktą sudaro keli atributai, jis vadinamas sudėtiniu raktu. Lentelėje gali būti keli atributų rinkiniai turintys rakto savybę, visi jei vadinami galimais raktais arba tiesiog raktais. Taigi lentelėje gali būti keli raktai. Vienas iš raktų paskelbiamas pirminiu raktu, dažniausiai trumpiausias. Lentelės l(R)={e1,e2,...,em} atributų aibės R poaibis V⊆R yra viršraktis, jei  ∀i,j=1,...,m ir i≠j yra teisinga nelygybė ei(V)≠ej(V) Funkcinė priklausomybė. Kai atributų aibė A eilutėje vienareikšmiškai apibrėžia atributų aibę B, tai priklausomybė tarp A ir B atributų vadinama funkcinė ir žymima A→B. A→B reikšia, jog A funkciškai apibrėžia B arba B funkciškai priklauso nuo A. Kairė žymėjimo pusė…

0 Comments
First design for 3d printer
Hex key T handle Drawing

First design for 3d printer

My first design for 3d printing! You can find it on a thigverse: https://www.thingiverse.com/thing:3560965 So that is why it might be a bit over engineered, bu hey, it is fun so who cares ;) I had some hex type key for automatic yard gate engine disabling and it that plastic handle that got broken over time. So I figured out that this fix could be a good practice to learn Fusion and make my own handle design. Some design decisions and conclusions if they have worked out or not: Hex key should be fixed to the handle by tightening nut and bolt. That worked out pretty well. I decided that I will split handle horizontally for two reasons: a) it is super easy to print both parts from flat surface without any supports and b) I can select different infill: 100% for bottom part that holds hex key and has to be strong enough and I can select something like 10% for top part that is basically a decorative part. I will use two pins to join top and bottom part. That did not work very well: pins got broken on assembly ( I forgot to make them 100% infill…

0 Comments

8086 disassembler using 64 bit assembly language

8086 disassembly application. Project done during computer architecture course. Project is done using nasm(yasm) 64 bit assembly and some c functions to handle input/output. I have chosen such technologies because I was curious about few topics: Learning about asm 64 bit programming Compiling assembly executable for windows 64 platform. During the comp architecture course we were doing assembly programming for a ms dos using dosbox. I was interested in making some executable code on a windows 64 platform. Linking assembly code to some higher lever programming language library. During the comp architecture course we were using dos api (int) to handle input, output and some other manipulations. For modern platform you could use windows api function calls or libraries from higher level programming languages. I have chosen to use c and use some basic c input output functions. Understanding assembly procedure calls on 64 platform and differences between win 64 calls and unix/posix 64 calls. Disassembling some simple c applications and exploriing how assembly code is constructed using c compile. To understand how some c function calls are made I have used some super simple c programs that I decompiled using gdb. This project can be found in github.

0 Comments

End of content

No more pages to load