jon

And I want to know, does it change something if I connected all the transistors' collectors together and then to +9V and all the three bases together to the 4.7 K connected to the ground and a wire going to pin 7 of the dual opamp? J.

Without the mic connected, voltage of pin 5 varies between 0 V and 5 V and there's no current on pin 6. But everything is connected well. I just don't get it... J.

I did the circuit again, but now all the LEDs are working together and when I tap on the electret mic, the LEDs seem to react inversely, meaning that the LEDs turn off when I tap on the mic. (And it's really not as sensitive as it was when it was working well...) I verified the circuit three times and I found no problems, but I don't know why it isn't working. J.

OK but the datasheet shows how to cascade two LM3915 in Dot Mode, does that mean the I can't change the mode to bar after? And if I cascade two LM3915, can I still use the 9V battery or should I change it with something with a higher value? I think I'll just keep it like it is for now... J.

And I want to know, if I add one or two other LM3915, how would I connected them to let them work properly and extend the range? And should I not include the AGC-based dual range (and where is it?) if I decide to add more LM3915? J.

Yes I did all those things, but I think the problem is on my weldings, maybe I connected some wires not correct or I connected some wires that should not be connected together, I don't know. I'll check them... J.

I don't know, that's the problem... There's too many weldings... J.

Do you think there might be any problem on your Veroboard schematic? Because it doesn't work... J.

Why is there an arrow-like thing on the (9,17) point? And what does it mean? J.

Ah ok! Now I understand why LEDs connected to pin 1 were always lighting... Thanks, J.

Where is R18 on the Veroboard circuit? J.

Thanks for everything! Everything is working fine till now! (and I hope not to have any more problems, and if I do I'll need more of your help...) But now I just have to understand your Veroboard drawing so I can reproduce it and finalize it all... Thanks again AudioGuru! J.

Ok, but I think the range of this Sound Level Indicator is between 15 dB and 45 dB because a pin dropped at one meter is 15 dB and the LEDs react to it. It even detects someone walking five meters away in another room, with the door of my room closed! And yes, all the LEDs light and turn off when the battery is week, I verified it. I think I can change the amplification by reducing the value of R5 or R8. J.

The Sound Level Meter works! The only problem is that it's too sensible, I don't think it's range is 45 dB to 95 dB, all the LEDs are reacting for all and every sound. Is there a way to reduce the amplification? And the other little problem is that LEDs connected to pin 1, 2 and sometimes 3 and 4 on the LM3915 are working all the time, even when there's no signal... Oh and the voltage of pin 5 when there's no signal is 0.04V and pin 6 is 0.5V. J.

Ok, I just completed the circuit another time. Now the LEDs seems to be reacting to the electret mic, but in another hand it works even when I remove the mic... The LEDs are lighting all at once and then they gradually stop and then gradually works, and it does that all time, none stop... I just don't understand what might be the problem... I'll continue checking it. J. (And I'll soon have the voltages...)