Maker Pro
Maker Pro

Help with LM386 Amp Circuit

McDroogie

Dec 25, 2012
37
Joined
Dec 25, 2012
Messages
37
I am trying to amplify my MP3 with the schematic pictured below. Can anyone tell me there are any errors? Except I've removed R3.
 

Attachments

  • IMG-20130112-00217.jpg
    IMG-20130112-00217.jpg
    148.3 KB · Views: 176
  • IMG-20130112-00218.jpg
    IMG-20130112-00218.jpg
    148.5 KB · Views: 191
  • IMG-20130112-00219.jpg
    IMG-20130112-00219.jpg
    148.8 KB · Views: 199
  • IMG-20130112-00220.jpg
    IMG-20130112-00220.jpg
    146.5 KB · Views: 214
  • IMG-20130112-00221.jpg
    IMG-20130112-00221.jpg
    144.6 KB · Views: 179
  • IMG-20130112-00207.jpg
    IMG-20130112-00207.jpg
    47.6 KB · Views: 190

davenn

Moderator
Sep 5, 2009
14,045
Joined
Sep 5, 2009
Messages
14,045
hi there :)

yup you have a few errors in your wiring up
now I can give you the answers directly or I can give you hints to help you fault find
and that would be a much better learning lesson ;)

1) follow you power supply from the + line on the proto board and through R1
what then can you see wrong with the capacitor C1, compared to the circuit diag.?
2) another capacitor wiring error .... look at the IC output on pin 6 going to the speaker
you have the capacitor there not wired to the way the circuit diag shows ... can you see the error

not to put too much on you at once ... lets sort those 2 things out for a start then we can look at the rest :)

Dave
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
Joined
Jan 21, 2010
Messages
25,505
One major issue is that your speaker is connected directly from the output to ground.

Note that in the circuit, the capacitor connects between the output and the speaker (in series). You seem to have connected them in parallel.

I suspect doing this is enough to prevent the circuit from working at all.

That is just the first thing I noticed. There may be other errors.

You need to be very careful in wiring to make sure that things are connected up the same way (unless you are skilled enough to know when it can be done differently).

Also, you'll find it easier if you place the positive rail at the top of the breadboard, and the negative at the bottom. This is the normal way a breadboard is used and it mimics somewhat how circuit diagrams are drawn. It also helps prevent problems caused by connecting things up to the wrong power supply rail.

I did notice that your soldering is a bit messy on the 3.5mm socket. Just be careful you haven't shorted anything out.

Don't take these criticisms too harshly, it looks like you're gaining the skills needed to breadboard circuits. Nobody is an expert overnight.
 

McDroogie

Dec 25, 2012
37
Joined
Dec 25, 2012
Messages
37
Thanks. I had trouble desoldering the wires from that jack, so I tried my best and just did what I could and added another few coats of solder.
 

McDroogie

Dec 25, 2012
37
Joined
Dec 25, 2012
Messages
37
So connect the C1's lead to ground, make sure its positive lead is the in same row as R1 and connect it to pin 6?
 

davenn

Moderator
Sep 5, 2009
14,045
Joined
Sep 5, 2009
Messages
14,045
One major issue is that your speaker is connected directly from the output to ground.

Note that in the circuit, the capacitor connects between the output and the speaker (in series). You seem to have connected them in parallel.

.

Steve .... grrrr

I was trying to get him to see that fault, mate ;) so he could learn to fault find :)

Dave
 

davenn

Moderator
Sep 5, 2009
14,045
Joined
Sep 5, 2009
Messages
14,045
So connect the C1's lead to ground, make sure its positive lead is the in same row as R1 and connect it to pin 6?

yes, positive of C1 and one side of R1 go to pin 6, the other side of R1 goes to + supply

now how about point 2, can you see what you have done wrong there ?


Dave
 
Last edited:

McDroogie

Dec 25, 2012
37
Joined
Dec 25, 2012
Messages
37
I'm confused. It should the the negative lead going to ground right? I have posted some pictures of my attempts.
 

Attachments

  • IMG-20130112-00222.jpg
    IMG-20130112-00222.jpg
    145.9 KB · Views: 182
  • IMG-20130112-00223.jpg
    IMG-20130112-00223.jpg
    145.8 KB · Views: 200

McDroogie

Dec 25, 2012
37
Joined
Dec 25, 2012
Messages
37
Here is a quick revision...
 

Attachments

  • IMG-20130112-00224.jpg
    IMG-20130112-00224.jpg
    153.3 KB · Views: 161
  • IMG-20130112-00225.jpg
    IMG-20130112-00225.jpg
    151.6 KB · Views: 174

davenn

Moderator
Sep 5, 2009
14,045
Joined
Sep 5, 2009
Messages
14,045
Here is a quick revision...

Thats much better :)

you also figured out what you did wrong with that output capacitor and fixed it
ie.... its supposed to be in line with the output and the speaker Well Done!! :)

now one thing to do and this is just for ease of layout....

put the positive supply on the other side of the board ie. keep the negative down the side where it is and move the positive to the other side. That is something that is common practice on breadboards and even on final PCB designs Keep + and -
as far apart as possible
THEN you can move R1 so it has a short hop from pin 6 to the + rail insteading of stretching the component legs way over the chip etc

it just makes it tidier and easier to follow :)

Dave
 
Last edited:
Top