Strange LED driving scheme

202

01:43:02

The cathodes of the LED row is connected to the base of a BJT without any current limiting resistor. Each LED gets a small current in every cycle, so there is some "ghosting"
From: https://mitxela.com/projects/tic_tac_toe

published 9 years ago

solartech

9 years ago

Please what is the part number of the transistor?

nemethakos

9 years ago

Hi solartech, I'm not the designer of this scheme, just run into it while browsing the net. On the authors web page there is a schematic and a lot of photos, but the type of transistor is missing. The only sure thing is that they are NPN types and the packages are TO-92. Knowing that the author was a university student when he made it, I guess he used some jellybean parts, for example 2n2222.

rich11292000

9 years ago

This doesn't need transistors. But the tic tac toe does.

solartech

9 years ago

Thank nemethakos.

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