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Topic: Using an LED driver to fire keys on a toy keyboard (Read 4614 times) previous topic - next topic


Worked like a charm in a test. Now I have another question that I might end up answering myself but just in case...
Can I just use 3.3v for each of the three v+ pins on the shift register? I'm lookin at this:

Which boils down to... what happens when my data line is 5v and my Vcc is 3.3v?


According to the data sheet for 74HC595 Vcc can be as low as 2Vdc so should work fine at 3.3Vdc.
Make sure it is HC part not HCT cause HTC is 5V.  You need to put the voltage divider on the data (serial in) line to get it near 3.3V on a high (like the suggested 1k-1.5k divider).


It turns out just making the rail 3.3v works (for now at least) and my multimeter reads 3.6v~ so shouldn't blow it... right? :) Maybe I'll lower it a bit.
Anyway, I succeeded in creating the most annoying thing in the world. I'll refine it ;p Lovin the Arduino and these forums, though. Shift Register FTW, BTW.

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