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Transistor power dissipation

Filed under: Uncategorized — Tags: , , , , , , , , , , — admin @ 2014-02-02 11:53

How to choose the right switching transistor for my application? It must withstand the current, generated heat and applied voltages. Current and voltage does not pose any problem. You have to use some calculations about the power dissipation. (more…)

Don’t be afraid of a long learning curve

Filed under: Uncategorized — Tags: , , , , — admin @ 2014-01-31 00:12

This post is a little bit different. It does not contain any how-to, know-how or data. It is a little thought that I came to after a recent experience. (more…)

PCB footprint dimensions

Filed under: Uncategorized — Tags: , , , , , , , , , , , , — admin @ 2014-01-22 14:39

Do you like DIY and default footprints in PCB CAD programs are not satisfying? Create your own. But what are the dimensions and placement positions? Datasheets and some calculations can help a lot. (more…)

Run complex command/process with killing previous

Filed under: Uncategorized — Tags: , , , , — admin @ 2013-11-07 11:05

When I run a Django testing server in a terminal it sometimes gets stuck and it can’t be killed with CTRL+C. Or I’m using SSH client in background mode for a secure proxy tunnel and I need to restart it from time to time. Searching manually for PIDs with ps and grep and killing them is a lengthy process. (more…)

OpenCV – convert projection matrix to maps

Filed under: Uncategorized — Tags: , , , , , — admin @ 2013-07-12 11:22

I created an application for a target hit evaluation using a webcam. The camera is never vertical to the target so there is a significant perspective distortion and I need a bird’s eye view. Fixing this with getPerspectiveTransform() and cv::warpPerspective() is easy but cv::warpPerspective() is very slow (at least for my purpose). (more…)

Compile optimized Debian packages

Filed under: Uncategorized — Tags: , , , , , , — admin @ 2013-04-09 10:51

Do you envy Gentoo users their tuning? Debian packages are mostly shipped only with a basic optimization (-O2) and for more generic CPUs. How about fine tuning for your CPU? (more…)

Fixing Ubuntu “Open with”

Filed under: Uncategorized — Tags: , , , , , , — admin @ 2013-03-03 21:01

First there was the annoying default “Wine Internet Explorer” for opening images. Why? I found the default source, I deleted it and then it was “Firefox”. Why??? I have different image viewers. Linux distributions are starting to behave like MSW. (more…)

Chroot PHP

Filed under: Uncategorized — Tags: , , , , , , , , — admin @ 2013-03-02 15:24

This is a poor man’s implementation of PHP environment chrooting. Apache’s suexec is too hardwired to user homes. Suexec is probably more secure but this is more flexible. (more…)

Detaching MS Windows libusb driver

Filed under: Uncategorized — Tags: , , , , , , , , , , , — admin @ 2013-02-20 10:20

It was easy to assign a FTDI device VID/PID to a libusb backend with Zadig. But detaching it from the libusb and assigning the original FTD2XX driver wasn’t so easy. Simple “remove device” in the Device Manager is not sufficient. When you plug back the device it will be assigned to the libusb again.

(more…)

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