As always, Audioguru, you helped me, thank you!Connect pin 8 to 0V then pin 7 will be +1.28V. Connect a 470 ohm resistor to 0V from pin 7 to set the LED currents to 22mA each.
Connect the top of the divider pin 6 to pin 7 so that the 10th LED lights when the input is +1.28V.
Connect a resistor from the bottom of the divider pin 4 to 0V so that the current in the divider creates a voltage of 38mV at pin 4 so the 1st LED lights when the input is +38mV. Connect a resistor to 0V at the input pin 5 of 1M or less to keep the input from floating high. The divider in the LM3914 is about 12k and the divider in the LM3915 is about 28k so adjust the resistor from pin 4 to 0V accordingly.
Absolutely WRONG!I went to the LM3915 datasheet (Block diagram page) and calculated about 26k (divider R1 is 22.63k), attached this to pin 4 and the other end to ground. I put a 820ohm from pin 5 (signal in) to ground.
No, you misunderstand me. What I meant by R1 was all of the resistors on page 7 (I have TI datasheet, so page 9) added together. R1 = 6.63 + 4.69+3.31+2.34+1.66+1.17+0.83+0.59+).41+1.0. So then R2 came out to be about 26k to make Vout 38mVAbsolutely WRONG!
You did not do what I said.
The block Diagram on National Semi's datasheet is on page 7 and does not have an R1.
The resistor from pin 4 to ground will have a fairly low value, about 820 ohms so that when the input is 38mV then the 1st LED lights. With no input then no LED should light. When the input is 1.32V then the 10th LED should light.
Pin 5 will float high if it does not have a resistor to ground. The resistor can be 1M, 100k or any value that is 1M or less.
The LM391x is designed to show audio signal levels, not radio signal levels. It will show the output of the audio level from a radio.
your circuit is extremely simple so many lEDs will be turned on and will look like a dim blur. All the audio level circuit I built with an LM3915 or two use one of the peak detector circuits shown in the datasheet so that the peak level is clearly shown.
Since you do not post your schematic then we are just guessing at the details. Is pin 8 connected to 0V? Then the 630 ohm resistor (not a standard resistor value) from pin 7 to 0V causes the current in each lighted LED to be 17.5mA.OK, thanks for the explanation. I get it now.
I've got something strange going on though. I have only one resistor between pins 7 and 8, 630ohms and a 2.2uF cap between pins 1 and 2. No other passives.
Since you do not post your schematic then maybe the supply voltage is collapsing when more than a few PNP transistors have 17.5mA of base current. You don't even say what is the output current of each PNP transistor. You don't even say what are the supply voltages and currenty capability.I'm using each output from the LM3914 to trigger a PNP which then triggers an LED panel. The trouble is that when all 10 panels are connected, output 9 from LM3914 causes panel 9 to occasionally blink quickly, out of order, before the rest of the panels.
Is it normal that one output could appear to trigger out of order for a split second? I say appear because I wonder if the switching time of the PNPs could be off from each other ever so slightly.