Question about LM3914 Display Driver

[dmccormick001]

Does anybody know whether or not the #1 LED output of the LM3914 doubles as an On/Off indicator as well as the lowest voltage indicator of the string? I have a simple circuit I built to monitor the voltage of my field box's 12 volt battery, and everything seems to be working just as I expected, except that the #1 LED stays partially lit anytime the circuit is connected. It comes on dimly, and stays that way as I adjust the input voltage down into the lower range, and then comes on as bright as the others were when the voltage drops down to the lowest point. It makes me think it's acting as an "On" indicator, but I checked the data sheet and couldn't find any reference to this feature. The circuit has nothing in it to cause this behavior, i.e. the #1 LED is connected directly to pin 1 of the chip just like all the other LEDs are connected to their respective pins (#2 to pin 18, #3 to pin 17, etc.) with no other parts or connections.

[vintage1]

Looking at the schematic, and reading the chip spec. that would appear to be the default when you have it in single LED mode, (one LED always on) but in bar mode,it looks like its possible to set a scale bottom by setting the voltage on pin 4.

[lazy-b]

I've been making a lots of Expanded Voltage Indicator using LM3914......and notice that the #1 LED alway has a very small Leakage current when it is OFF States, to minimized the Leakage current from Lightning the #1 LED, I installed a 330 Ohms Resistor across the #1 LED.......Works Flawlessly.

I do not know why there is alway a Leakage current on #1 LED only......a single resistor across the LED seems solve the problem.

[dmccormick001]

Thanks. I wasn't sure if my IC was bad, or if it was designed that way, or what. Now to find a resistor.....

[dmccormick001]

I've been making a lots of Expanded Voltage Indicator using LM3914......and notice that the #1 LED alway has a very small Leakage current when it is OFF States, to minimized the Leakage current from Lightning the #1 LED, I installed a 330 Ohms Resistor across the #1 LED.......Works Flawlessly.

I do not know why there is alway a Leakage current on #1 LED only......a single resistor across the LED seems solve the problem.
I tried the resistor, but it seems to disable the #1 LED completely.........

If I'm going to go that route, I might as well just omit the #1 LED...........

[Dan Baldwin]

Try a 10K resistor.

Dan