July 31st, 2009

Panda Inside

LM 3914? (Part 2)

(Part 1)

Ok, on closer examination, it can be set to show 0-1.2V by adding a single resistor. (1.2 apparently being the minimum.) Meaning a step of 0.12V between LEDs. I need a step of 0.04V between LEDs.

Now, if I use a 3x voltage multiplier of some kind on my source, that lets me use a step of 0.12. But then I need to set an offset voltage to the LM3914, so it displays the correct range (1.86-3.06V I believe?)

I know it /can/ be done (otherwise cascading them wouldn't work), I'm just not sure how to do it without needing to add extra (useless) LM3914 chips. (Especially since the local electronics store seems to want $8 ea. for them!)

Also, about the outputs: Can I use one red LED on 3 outputs (2.34-2.46, 2.46-2.58, and 2.58-2.70 after the multiplier)? Or do I need a separate LED for each? And can I let the unused outputs (below 2.34 after the shift) just float? Or do I need to stick something on them, even if it's just a generic non-light-emitting diode?
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