I’ve sent a little LED dimmer PCB to OSH Park service. For 4.6 USD it is a great deal. Vias are 0.8 mm in diameter and 0.3 mm drill. SMD components are 0805. The result? Very good. (more…)
Transistor power dissipation
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…)
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Don’t be afraid of a long learning curve
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…)
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PCB footprint dimensions
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…)
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Xfce, monitor change, blank screen
Have you changed you monitor and you can’t access your desktop after login because there is only a blank screen? (more…)
Run complex command/process with killing previous
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…)
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OpenCV – convert projection matrix to maps
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
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…)
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Fixing Ubuntu “Open with”
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…)
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