Bass reactive LEDs

Thread Starter

AkshayVernekar

Joined Jun 16, 2013
1
Hi all,
I am currently working on a project that involves filtering the LOW frequency(<200Hz) using a LPF and amplifying the output using a LM741 and passing the output to LEDs. i tested the same circuit with Multisim and it is simulated correctly. but now, when i power up the circuit the LEDs light up without any input voltage . i checked the connections and the connections are correct. Please help
 

GopherT

Joined Nov 23, 2012
8,009
In the off-state, the 741 does not turn off completely (it may even be on enough to keep a red LED on).

You will need to post your circuit so we can give you advice to tweak what you have. Otherwise, there are many ways to start over - you don't want to do that.
 

GopherT

Joined Nov 23, 2012
8,009
A pair of pull-down resistors in series will work best. That way, when the 741 swings within 2 volts of ground, the pair of resistors making the voltage divider can swing much closer to ground. A 100 ohm and 1000 ohm resistor will allow the point in between to reach 0.2 volts (approximately).

Note that the more modern standard op amps can provide about 30 mA, the old 741 should be kept well below that, If I remember correctly. Use an audio amp lm386 if you need more power. You can also add a transistor to the output of the opAmp to boost current to drive more LEDs
 
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