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Topic: Opamp setup doubt (Read 10328 times) previous topic - next topic

ChrisTenone

Ok I connected some jumpers and got their ohms to be 1Ω.  The issue Im dealing with is that because I had a split power supply set up and Im connecting the opamp's GND to vcc- on the split supply, I have some things connected to ground and others connected to vcc-.

Connected to Ground (midway between vcc- and vcc+):

mic
speaker
10uF cap on the way to v+ opamp
opamp negative feedback loop

Connected to Vcc- from split supply
GND opamp
100uF (Vo) thru 10k R
2n3906 collector

ChrisTenone, I read your reply #87 but i want to make sure I understand it right before firing this up.  According to what I have, GND on opamp would be connected to -9V as well as the 100uF (Vo) thru 10k R and the 2n3906.  Should I move these to real ground which will actually be 0V because it is in the middle of the 2 9V batteries?

Thanks


Most opamps use a dual power supply, V+ and V-. If you make V- equal to zero volts, it is referred to as a single supply opamp. You can use the LM324 either way, you just won't get any negative voltage output with a single supply.
What, I need to say something else too?

Marciokoko

Right, but at this moment I still have the 2 batteries making up a split supply +9V and -9V.  Thats what I mean by "I have connected to GND and some connected to Vcc-).

Im thinking I should move the:

GND opamp
100uF (Vo) thru 10k R
2n3906 collector

to real GND from the supply, 0V.

Southpark

#92
Aug 11, 2016, 09:15 am Last Edit: Aug 11, 2016, 09:16 am by Southpark
Right, but at this moment I still have the 2 batteries making up a split supply +9V and -9V.  Thats what I mean by "I have connected to GND and some connected to Vcc-).

Im thinking I should move the:

GND opamp
100uF (Vo) thru 10k R
2n3906 collector

to real GND from the supply, 0V.
The two 9V batteries will be connected like this...

+ -******+ -


The starred symbols represent the connecting wire between the - terminal of battery #1 and the + terminal of battery #2.


The wire will become the '0V' side of things (itself).

+ -*******+ -
          *
          *
          *
          *0V

The + terminal battery #1 will be +9V.
The - terminal of battery #2 will be -9V.

The connecting wire itself will be 0V.

And, if we're working with arduino...... we also usually connect that wire (0V) to the GND pin of the arduino as well.

ChrisTenone

...

And, if we're working with arduino...... we also usually connect that wire (0V) to the GND pin of the arduino as well.
Totally correct. But it needs a caution!!!

Do not hook up the + or - voltages to an Arduino. Both +9 volts, or -anything can fry things in the Arduino world.
What, I need to say something else too?

Southpark

#94
Aug 11, 2016, 10:16 am Last Edit: Aug 11, 2016, 10:18 am by Southpark
Totally correct. But it needs a caution!!!

Do not hook up the + or - voltages to an Arduino. Both +9 volts, or -anything can fry things in the Arduino world.
Excellent word of caution Chris. Yeah.....definitely don't hook up +9 or -9 volt to the arduino digital or analog pins.

Marciokoko

#95
Aug 11, 2016, 07:12 pm Last Edit: Aug 11, 2016, 07:12 pm by Marciokoko Reason: image
Yes I understand how the split supply works from +9v to 0V in the middle to -9V.  Its just that since my original setup had opamp-Vcc- going to -9V and the new setup calls for connecting the "100uF (Vo) thru 10k R" and the "2n3906 collector" to Vcc-...

I guess what Im wondering is, should I do this then:


Basically break the connection from the opamp-Vcc- to -9V, and reconnect it to GND then, but leave everything else connected to -9V?

Southpark

#96
Aug 11, 2016, 07:58 pm Last Edit: Aug 11, 2016, 08:00 pm by Southpark
Basically break the connection from the opamp-Vcc- to -9V, and reconnect it to GND then, but leave everything else connected to -9V?
Should be like this.....


polymorph

Steve Greenfield AE7HD
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