OpAmp oscillator circuit

[eng.abu_muslem]

Kindly help me!
What is the problem in this design?

 

[Harald Kapp]

Welcome to electronicspoint.

Typically we work the other way round: you tell us what the problem is and we try to locate it.

In this case, look closely at the power supply of U1:A and at R4. This is not correct. A correct circuit is shown here.

Also note: there is no NE555 in your schematic, so I changed the title. This is also not a microprocessor circuit, so I will move the thread to another of our fora.

Regards,
Harald

 

[hevans1944]

Also look at U2, which appears to be installed backwards: the supply, Vcc, is connected to the output, pin 3, while the oscillator/amplifier circuit is trying to draw power from the input terminal, pin 1, of U2. D3 also appears to be installed backwards if the intent is supply power from Vcc to whatever the round thingy is (piezoelectric transducer? speaker? connector?)

 

[Harald Kapp]

Vcc, is connected to the output, pin 3

Good find, escaped me.

D3 also appears to be installed backwards

It definitely is.

I should have spent more time with the schematic

 

[hevans1944]

... I should have spent more time with the schematic

No, Harold, the OP should have spent more time with the schematic. And perhaps explained what this circuit was supposed to do, if it actually worked. TWOFT to spend any more effort trying to "analyze" it.

 

[davenn]

x

 

[hevans1944]

Clarification: TWOFT = Total Waste Of Free Time

 

[davenn]

LOL wondered what that acronym was for

 

[Arouse1973]

Hello
This is how I think your oscillator circuit should look, operating from a single supply. I assume this is some kind of PWM circuit driver?
Thanks
Adam

 

[davenn]

why would you have the "out" there ?

 

[Arouse1973]

PWM controller. The following stage samples the RC time constant triangle ish wave, so you can vary the pulse width. I guess that's what he is doing?
Adam

 

[davenn]

no, why would you have the output coming off an input pin of the op-amp instead of the output pin ?

(maybe Im missing something?)

 

[hevans1944]

no, why would you have the output coming off an input pin of the op-amp instead of the output pin ?

(maybe Im missing something?)

I think what Adam is saying is the following stage (which he didn't show) uses the triangleish wave across C1 to compare with a DC reference to create the PWM waveform... or sumthin' like that. What the heck is the round thingy the MOSFETs are trying to drive? Arrgh! I said I wouldn't waste anymore of my free time on this!

 

[davenn]

What the heck is the round thingy the MOSFETs are trying to drive?

Presumably the motor ??? haha

 

[davenn]

D3 also appears to be installed backwards if the intent is supply power from Vcc to whatever the round thingy is (piezoelectric transducer? speaker? connector?)

rereading that comment from you
I bet that diode is probably supposed to be in parallel with the ummm motor ?

as you have said ... wired as it is that thingy aint gonna work


ohhh dear

 

[Arouse1973]

I think what Adam is saying is the following stage (which he didn't show) uses the triangleish wave across C1 to compare with a DC reference to create the PWM waveform... or sumthin' like that. What the heck is the round thingy the MOSFETs are trying to drive? Arrgh! I said I wouldn't waste anymore of my free time on this!

Yep correct,cheers Hop. The circuit I drew what the correct way to draw his original oscillator circuit.
Thanks
Adam