LM3915 and LM386 problem, is this circuit ok?

[denno]

I found this circuit on the internet, and I wired it all up on my bread board, but it didn't work correctly..

When I applied the 9V, the LED's would light up, and the sequentially turn off. I couldn't get any response through the mic to show up in the LED's at all. I took it apart and re-wired it, but again, nothing..

I'm not sure if I'm using the right components either though? Just from looking at the schematics, I got the correct numbered components, but not sure if they're exactly what is needed or not?

The circuit is attached, and here are the components I used:
1 x 10k Linear Taper Rotary Potentiometer
2 x 10uF 100V 85°C ELECTROLYTIC CAPACITOR (is positive the longer lead - the opposite side of the capacitor to where the grey line is)
2 x 1uF 25V TANTALUM CAPACITOR
1 x LM3915
1 x LM386
various 1/4W resistors (not all of them the exact values, but I've used a couple of resistors in series to add up to close the required resistance)

I purchased all these components off eBay to make this one circuit, and wasn't too happy when I wired it all up and it didn't work lol.

So basically, are my components correct? and is the circuit good for the desired vu meter?
Again, this isn't my circuit, and I'm not trying to claim it to be..
Thanks
Denno

 

[audioguru]

Instructables are designed by people who cannot read a datasheet and they know nothing about electronics.

1) R5 was wired as a rheostat with a very small range of adjustment. It should be wired as a volume control. I show how. It should have an audio taper (logarithmic taper) but try your linear one set to about half-way.
2) The new position for R5 makes R3 do nothing so R3 can be removed.
3) R4 does nothing and should be replaced by a piece of wire.
4) Pin 7 (which is connected to pin 6) should have a resistor to ground to set the amount of current in the LEDs. I show a 330 ohm resistor which sets the current in each LED at 28mA which is fairly bright. But the LEDs are lighted for only half of each cycle so will appear to have a current of 14mA each.
But if all the LEDs are lighted then a little 9V battery will not last long.
5) The circuit was missing an important supply bypass capacitor. I show 33uF but you can use 10uf to 100uf.

The electret mic should have 2 pins, not 3 pins. One pin connects to its metal case and that pin should be connected to ground. The other pin is the output.

 

[denno]

Thankyou very much. I'm very eager to try this now. I will have to wait until tomorrow or sunday though as it's very late now lol. I will post back with (hopefully) positive results.

Thankyou very much .

 

[Vizier87]

Instructables are designed by people who cannot read a datasheet and they know nothing about electronics.

Me like, AG.
Instructables are designed for that kinda crowd.

 

[denno]

Ok, so I'm trying to hook this up, but I'm getting confused. I'm probably thinking too hard about it and making it difficult, but what I'm having troubles with is:

The 33uF cap, how do I connect that up on the breadboard? It looks like it just goes from 9V to ground.. And then the 330Ohm resistor is connected to ground and the line between pin 6 and 7 (which I think means I can just put the resistor to the connector at either pin 6 or 7..)

Also, pins 4, 8 and 2 are all connected to ground? As well as the bottom side of the POT?

Sorry for my ignorance, but I've had very little experience with using breadboards and how to make it easy to hook up circuits..
Thanks

 

[audioguru]

The 33uF cap, how do I connect that up on the breadboard? It looks like it just goes from 9V to ground.

Yes.

And then the 330Ohm resistor is connected to ground and the line between pin 6 and 7 (which I think means I can just put the resistor to the connector at either pin 6 or 7..)

Yes.

Also, pins 4, 8 and 2 are all connected to ground? As well as the bottom side of the POT?

Yes. Of course the negative wire from the battery also connects to ground.

 

[denno]

Well in that case it doesn't work. I'll check my connections again, but I thought I was careful the first time around..