Okay, so I have lots of experience with LM3915 IC, it was the first IC I ever used and have made a bunch of gifts and displays with them. Now, the cool thing about this IC is the ability to display in either Bar-Graph-mode or in Dot-mode. I usually hardwire Pin9 to Pin3, which keeps it in Bar-Graph-mode, but yesterday I built a little pocket-version VU meter and this time I hooked a switch up to Pin9 so that I could toggle between Bar-Graph-mode and Dot-mode. Bar-Graph-mode works perfectly, but Dot-mode doesn't. When I flip the switch, it goes SORT OF into dot-mode; where there's always about 4 LED's on, but not the single LED. This is weird because I had dot-mode working perfectly over christmas break (was making a present for my brother) but right now, i can't seem to get it to work.
Here's the circuit I've been using:
And here's the datasheet of the IC:
http://www.national.com/ds/LM/LM3915.pdf
I've been using 6V with the circuit, but have tested up to 12V without different results. And for the record, IN THIS PARTICULAR BUILD, instead of using individual resistors for each LED, I used a single 100-ohm resistor, hooked up to the Positive strip that runs down the right side of the diagram, but I don't think that's the problem, because Pin3 (Vcc) and Pin2 (Gnd) are still getting direct power from my power supply.
Thanks to anyone that can offer an insight. -Joe
Here's the circuit I've been using:
And here's the datasheet of the IC:
http://www.national.com/ds/LM/LM3915.pdf
I've been using 6V with the circuit, but have tested up to 12V without different results. And for the record, IN THIS PARTICULAR BUILD, instead of using individual resistors for each LED, I used a single 100-ohm resistor, hooked up to the Positive strip that runs down the right side of the diagram, but I don't think that's the problem, because Pin3 (Vcc) and Pin2 (Gnd) are still getting direct power from my power supply.
Thanks to anyone that can offer an insight. -Joe