Cannot increase LED current with LM3916 Vu Meter chip

[Mahdi.H]

Hi all,

I am using this circuit as an electret preamp... **broken link removed**
Any comments? I don't really know enough to determine if this is a good circuit or not.

I am then using an LM386 for power amplification and finally using an LM3916 to create a 10 LED Volume meter. It seems to be working but the LEDs are not bright enough. I have read the LM3916 data sheet and from what I understand about the LED current formula given is that the current should increase if I lower resistor one, but the exact opposite happens!

Strangely, when I put in a large value for R1 the LEDs have a weak brightness (about 1mA through them). But when I lower the resistance (to about 1000ohm) the LEDs are very very dim and some wont even turn on (I guess because of diode threshold voltages).

Can anyone please help me make them brighter?

Thank you

 

[dr pepper]

Do you have a schematic for the lm3916 part?
From what I remember the current through the leds is programmed by the current drawn from the reference terminal on the '3916, recalculating the reference resistors can be done to increase brightness, at least up to a point.

 

[alec_t]

the LEDs are not bright enough

Are you using a peak detector circuit?

 

[Mahdi.H]

The schematic on the second page is what I'm going off - https://www.electro-tech-online.com/custompdfs/2013/02/lm3916.pdf

The highest I can get the LED current seems to be about 1mA

 

[Mahdi.H]

No I'm not using a peak detector circuit yet, I will probably add one soon, but even if I do I don't think it will fix the LED current problem

 

[ronsimpson]

What supply voltage are you using on the LM3916?

 

[Mahdi.H]

9V battery

 

[ericgibbs]

9V battery

What resistor values are you using for R1 and R2.?

 

[alec_t]

No I'm not using a peak detector circuit yet, I will probably add one soon, but even if I do I don't think it will fix the LED current problem

No, it won't fix the LED current problem, but it will make the LEDs seem brighter because they will stay on for longer.