In Desperate Need Of Assistance

[kavkav]

Hi, I am new to circuits so please bare with me. I am trying to build something that gives off a specific sinusoidal frequency with high amplitude like an oscillator or an inverter. However I have attempted several different oscillators and ended up with failure. Either it didn't work or the oscillator only oscillated for a fraction of a second. Currently i am working on a quadrature oscillator with schematics from this website:
**broken link removed**

it is the diagram on the bottom right.

However when I built it, nothing happened. I checked the schemstic a hundred times and my circuit was correct. However there is one issue. I am not oto sure about the ground symbol. Is it the same as connecting all the ground symbols together then to the negative end of a battery? because i treid that and i connected the output to the positive end of the battery and used a tester to test it but it was not giving off sny frequency. I also tried reversing the output and input connection to the battery but still nothing. I the circuit with an output using a circuit simulator and it worked:

Circuit Simulator Applet

is the simulator wrong? I have no clue but i doubt it would be.

DETAILS
my DC battery: 6v 1.3Amps
my resistors: 10 Kohms
my capacitors: 2.2uf
my desired frequency: approx 7 hz
my op-amp: MC1741CP1 ZKQAG811 (then it has some M symbol below)
my second op-amp: LM741CN (then some ST symbol) 88916

my op amps look exactly like the one on this website:

The 741 Operational Amplifier

As a last note of detail, my capacitors 50v on them. I'm assuming this means it can handle up to 50v rather "only work with" 50v. so if someone could clarify that for me, thanks.

In general terms, I'm just trying to make something that gives a desired frequency of 7hz with high amplitude/current. If you know a better way or a simpler oscillator that will give me continuous oscillations PLEASE let me know. Also if you could clarify my question about the ground symbol that would be great. Or if you can figure out why my quadrature oscillator is not working that would also be greatly appreciated. Thanks.

 

[KJ6EAD]

Using those component values, I calculate an oscillation frequency of 0.035 Hz. That's less than 2 cycles per minute! It's not what you wanted. I suspect a math or unit conversion error.

f = 1/2πRC where R is in ohms and C is in Farads. 10kΩ = 10000Ω and 2.2μF = 0.0000022F.

The grounds are all the same potential as the negative pole of your battery in this circuit.

Also, in your schematic, R1 needs to be less than R.

By the way, a 747 op amp is a dual version of the 741, which you have two of by different names. **broken link removed**

You are correct about the capacitor voltage ratings.

If you want "high current" output, you will need an appropriate transistor on the output. The 741 won't drive much, especially with such a low power supply voltage. **broken link removed**

I'm not trying to discourage you here but I'm curious, why are you trying to build a circuit suitable for a second year electronic student when you clearly don't understand some of the basics that would be considered first year material?

 

[kavkav]

Thanks a lot for the reply. I got a different answer in my calculation:
capacitor after conversion is 0.0000022 farads and resistor after conversion is 10000 ohms
then if you make 2(pie) = 6.28 you get f=1 / [(6.28)(0.0000022)(10000)] which equals out to approx 7.2hz

I just want to clarify a few things,
so R1 has to be less than hte other resistors but how should i do that exactly, i did acknowledge that so i made the wires connected to R1 a lot thinner and I don't know if that was enough but how would you decrease its resistance or should i use a less resistant resistor and if so, how do i deterermine by how much.

Regarding the op-amps, do you mean my op-amps are fine to use even though they are different names? and also the 747 link you sent me, do you mean i should replace both my 741s for a 747 or is it okay if i just stick with the two 741s? and for the 741 link i can use that to determine the opamp charateristics for all 741s?
Lastly, for increasing my amplitude/current, do you mean i need a suitable transistor on my output or in the circuit itself?

lol and if you are wondering why i am going way out of my head there is a good reason. I am a first year mechanical engineer but i am not doing this soley for the sake of learning. I have an idea i'm trying to make but i didnt know much about circuits and i didn't have anyone that can help me so i had to learn from scratch but the whole point of this is so i can test out my idea and if someone was able to build it for me i wouldn't be even attempting this.

 

[KJ6EAD]

I did the math again and got what you did.

Just make R1 the next lower standard value (9.1kΩ). I'll assume your resistors are the typical 5% tolerance type so the low end of the tolerance for a 10kΩ resistor would be 9500Ω and the upper edge of the tolerance for a 9.1kΩ resistor would be 9555Ω. There's a slight risk of overlap but I'd accept it.

Regarding the op-amps, do you mean my op-amps are fine to use even though they are different names?

Yes, they're both the same thing from different manufacturers.

do you mean i should replace both my 741s for a 747 or is it okay if i just stick with the two 741s?

Either way is fine. I prefer to use a single package because it looks neater.

for all 741s

Yes. A 741's a 741. Pick a datasheet you like from whichever manufacturer you like.

for increasing my amplitude/current, do you mean i need a suitable transistor on my output or in the circuit itself?

On the output.

I am a first year mechanical engineer

That makes sense. Something infrasonic, like Keanu Reeves in Chain Reaction with his ultrasonic sonoluminescent cold fusion apparatus, only different.

 

[kavkav]

thanks a lot you cleared up many things. And now that you mentioned the Keanu Reeves thing, that leads me to another question. I'm actiually working with electromagnetic waves rather than sound. I know when you use a light dimmer, you decrease voltage AND current thus making the light "dimmer" so i assumed a higher current will give an electromagnetic wave a higher amplitude which leads to my quesiton. If you use a transistor for increasing the amplitude for a sound wave, does it do the same for an electromagnetic wave? Or would i have to have a high current to begin with. I wanted the amplitude of the wave to be produced by a 1amp current. When using a transistor, does it increase current, or does it just increase the amplitude of a sound wave?

 

[KJ6EAD]

Sound, light, microwaves, electrons in a wire; it's all electromagnetic energy. You don't say anything about what kind of transducer you're feeding but generally amplifying a voltage will cause the current to increase according to Ohms Law. You don't start with a high current, you start with a high enough voltage to create that current in the impedance you have.
Ohm's law - Wikipedia, the free encyclopedia

The wavelength of 7 Hz is something like 40 million meters!

 

[kavkav]

Thanks. I think I know what I gotta do now