Electronics > Projects, Designs, and Technical Stuff

FE5680A LED Buffering

(1/1)

Hrvoje_CRO:
Hello everyone!


So i made a circuit based on this schematic: https://i.postimg.cc/cLJZxwtF/LED-Buffering.jpg The circuit is powered off course by using 7805 regulator. The circuit works but only for LOCK indication, 1PPS indication LED is always ON. I have checked on breadboard connections and everything is OK.

What am i doing it wrong?

Thank you!

DaJMasta:
Your PPS input signal is all wonky.  You have nearly zero volts on it at all times thanks to the resistor divider, and your diode on the input prevents current from coming in to change that.  I think you're trying to use the diode and resistors to invert the input signal... but there are a lot of extraneous parts.  I don't the polarity of the PPS signal is usually significant, either, but you can reverse it by reversing the LED direction and putting it to ground if desired.

I'd remove:
D2, R12, C6 (and R5, really)
then
D3 and R14
then probably change R13 to a lower value - only really necessary to limit power output/current driven into the far side, so enough to protect the chip should be plenty.  Maybe putting that 47 Ohm resistor in place of R13 is about right, but it depends on your potential load.



As a little extra aside, R8 does basically nothing (a current limiting resistor or voltage divider should be on the previous stage if needed, as it is right now it doesn't really protect anything), R7 (like R5) is only useful if your circuit can expect to be run without the inputs attached, and C4 doesn't really serve a purpose.  Maybe C6 or C4 should be used to bypass the supply of the IC instead.

Navigation

[0] Message Index

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod