Hi,
I'm a electronic newbie. I repaired a couple of home electronic stuff and in general I would say that I have "basic" electronic know how.
This is my first electronic DIY project.
I planned to build a simple DIY LAN cable tester based on a 555 and 4017. There are a couple of different designs available on the internet.
I liked the 8 LEDs approaches most. I know 4 LEDs would be enough but more LED -> more fun.
I finally ended up with the following schematic (not based on 555):
http://archive.siliconchip.com.au/cms/gallery/article.html?slideshow=0&a=30474&i=4Studying the 4017 datasheet I concluded that the schematic above is on the edge if not above the manufacture’s maximum current specs.
So, I planned to switch a NPN transistor instead of the 3 LEDs directly.
But there is a problem which I couldn't fix. In case of the design above only one 4017 output pin is V+ all other Pins are GND all the time. That is how one LED on the end of the wire lights up. Because all other pins are GND it is also possible to notice sequence changes.
How can I achieve the same with switching transistors instead of the LEDs directly? My last thought (before I gave up) was that I need at least 3 transistors 2xNPN to switch to ground by default and a PNP transistor to switch V+.
There must be an easier solution.
Looking forward for your feedback.
Kind regards
daskorn