LCR-T4 transistor tester original firmware

Bought cheap transistor tester from eBay and currently experimenting with firmware updates. I was able to program it with this version of Markus transistor tester firmware: https://github.com/svn2github/transistortester/tree/master/Software/trunk/mega328_T4_v2_st7565 To build, use a WinAVR programmers notepad, open Makefile and select Tools->Make all. At first, was getting weir errors, but after adding msys-1.0.dll to \WinAVR-20100110\utils\bin everything built ok. Before doing firmware experiments, I have made backup of original firmware, if somebody needs it, you can download it here: Code Data Config I tried to reflash original firmware and it worked fine. For programming…

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Modify Arduino 5v relay module to work from 3.3v

I am implementing a power-off function for my Ender 3 using OctoPi. For that, I need a relay and I happened to have one. Unfortunately, after connection relay to Raspberry Pi GPIO pin, the relay was always on and not listening to any commands from OctoPi. It appears this module was designed for 5v logic levels and Raspberry Pi works with 3.3v logic levels. After investigating relay one can see that its circuit is: For JC817C forward voltage Vf=1.2V and forward current If=20mA For Raspberry Pi output high (when VDD…

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Learning the Art of Electronics, Week 2

[latexpage]  2L1.1 Ok, I  form a simple low pass filter using unknown RC values. Then I measure time constant using scope and 500Hz square wave. Time constant is a time it takes for a voltage to reach ~63% of its total value. Measured time constant using RIGOL DS1054z is 0.268ms ( measured using manual cursors: I set Percent for Vert. Units, then Set range of the wave with vertical cursors and then measure time to rise to ~63% (bx-by) ) Measured time constant using Tektronix 2221A is 0.270ms ( I…

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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)…

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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…

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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…

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