Project with 3914. ???

[audioguru]

On the planet Mars they don't sell common electronic parts.

 

[HTAluvBeBeo]

Hanoi, vietnam:|
Do you know my country
I asked almost sellers in the market, but they do not have 3915 or 3916

 

[TheVictim]

What you might want to do is buy a value pack of linear IC's from a supplier. You'll get older and more common parts that you might have to work around, but you'll get a good supply. Futurelec's linear IC pack is around $5, and it will ship in a package under 13oz so you can probably get it shipped over there for not TOO much.

You can make just about anything from these common parts, but you might sacrifice some performance for using older types. "Back in the day" there were 5 IC's you should never be without. 741's, 324's, 555's, 386's and 74LS00's. 2N3904 and 2N2222 transistors are also extremely common. I'm just getting back into electronics, but I still find these are parts I simply cannot do without.

 

[HTAluvBeBeo]

TheVictim, I think that all of IC you listed will be found in my city easiy
In the schematic that audioguru corrected, If I add R1 to link pin2 and GND, all leds will light up. they do not dance with music
If I remove R1, everything seems to be better
So, why???

 

[Nigel Goodwin]

Because R1 sets the gain of the opamp - how large is the signal you're applying to it? - notice the diagram says 200mV maximum.

 

[HTAluvBeBeo]

Minimum scale of my very cheap VOM is 1 to 10 V. So I can not measure the input. But the input is headfone on my soundcard. I could borrow one miliVolt meter to measure it Thank you
So if the voltage exceeded 200mV, What should I do?

 

[audioguru]

Minimum scale of my very cheap VOM is 1 to 10 V. So I can not measure the input. But the input is headfone on my soundcard. I could borrow one miliVolt meter to measure it Thank you
So if the voltage exceeded 200mV, What should I do?

Turn down the level control at the input of the circuit.

 

[HTAluvBeBeo]

I did, but even when R1 was in the circuit and I mute the sound, all leds light

 

[HTAluvBeBeo]

I have just had some change
value of P1 is set to be as small as possible
R1 is 100k instead of 10k
And it worked quite good BUT
One more question, (sorry about many stupid questions)
At the first period, when I mut, all leds off
But after minutes, when I mute, one or two led still on
I change the C1 with new one, and everything seem to be K, but after minutes, prolblem happened. so, Why, and the solution is...??

 

[audioguru]

P1 is a volume control. If it is turned down then the circuit should not have an input. But you say it worked quite good. Then the pot is wired wrong.

With the pot turned down or when there is no signal then pin 3 of the LM358 is 0V. Then the input pin 5 of the LM3915 is also 0 and it should not light any LED.

 

[HTAluvBeBeo]

The POT: pin 1 to C1(connetec with the signal from my sound card), pin 2 to pin 3 of 358, pin 3 to GND
but about the C1, why after some minutes, the led 1 and 18 were still light, and I changed C1 with new one, everything seem to be OK, but after that, problem still happend:-?

 

[audioguru]

An electrolytic capacitor can hold a charge even after it has been discharged. Try tantalum capacitors for C1 and C2.

 

[Sceadwian]

Yeah, it's called dielectric absorption. I guess the electrons actually permeate the insulation material and after disconnection from the circuit will gradually recharge the capacitor.