Audio Level Meter to control non-LED lights

Thread Starter


Joined Jul 18, 2006
Ok, first of all I'm a total beginner (but with a good sense for things), so please bear with me.

I'm interested in building a simple Audio Level Meter. I've found several scematics and the proper IC (i think so at least). However, all of these are to control LEDs that are attached to the circuit board itself. What I want to do is to use the circuit to control seperate lights that have their own power which is not coming from the circuit.

here is an example IC that i found which I think it close to what I want:

however, I don't really know what I would need to do differently. Basically I want the lights to function just like the LEDs would, to turn on when the audio level passes a certain level. However the LEDs draw their power directly from the circuit board, where as I just want the audio signal to turn the appropriate lights on and off which are powered seperately.

Any help would be greatly appreciated. Please let me know if I left anything out.


Joined Jun 30, 2006
This says you can drive an ordinary lamp. If you need more power then use the output to drive a transistor, for more power use a relay.

The LM3915 is very versatile. The outputs can drive LCDs, vacuum fluorescents and incandescent bulbs as well as LEDs of any color. Multiple devices can be cascaded for a dot or bar mode display with a range of 60 or 90 dB. LM3915s can also be cascaded with LM3914s for a linear/log display or with LM3916s for an extended-range VU meter.


Joined Jan 10, 2006
AC or DC..? What Voltage, what Wattage..??.
If it is low voltage DC, then probably a PNP darlington on each channel with the emitter connected to the supply, the base connected via a 1k resistor to the chip output (I think these chips have an Open collector style output..???), something like a 10k resistor from base to emitter (may have to experiment to make sure lamp turns off), the collector going to the lamp (other side of lamp to -ve), and the -ve of both lamp and chip supplies tied together...
If AC, (low...... or mains...although as a beginner NOT RECOMMENDED) then opto-isolators to triac to bulbs...AC totally separate from chip circuit but still LETHAL !!