Hi guys,
I am a relative beginner trying to make a simple triangle wave (audible frequency) oscillator using TL082 op amps. My efforts on this front have been driving me a bit nuts.
This is the schematic I decided to use: http://chemelec.com/Projects/Osc-2/Oscillator-a.png
I know that op amps like this one use both + and - voltage and I have never dealt with a bipolar power supply before. Based on what I have read recently, however, it looks like just by following this schematic the two 10k resistors on the left will be dividing the voltage to set up a virtual ground and provide the + and - voltage the op amp needs.
So I built the circuit on my breadboard and it did not oscillate at all. I used a 12v regulated ac/dc adapter and just connected + tip to where it says "12 Volts DC" on the schematic and the ground symbols to the -, as I normally would. It looks to me that this schematic was designed so that a person with zero understanding of the concept of bipolar power supplies could just build it like any other circuit and it would still work, so that is what I did... am I missing something though? Is the negative supposed to be hooked up to something/somewhere else?
The only thing I did differently from the schematic was that I didn't use a tantalum capacitor because I didn't have one. I used a 1 uf electrolytic at first, then tried it with a few ceramics in parallel to add up to 1 uf, with no change. However, I figured this couldn't be the problem because it seems like it is just a decoupling capacitor, and either way it was still the right value.
I checked the voltage at the point that is supposed to be the triangle wave output and it was steady at 10.52 V. I checked the squarewave output and it was exactly the same. I didn't do the calculations but I'm guessing that is nothing more than the result of the resistors that it has passed through up to those points. I checked all my connections on the breadboard and had a friend (with about as much experience as me, but who also has a basic ability to read schematics) check them too. I even looked at the PCB image on the site where I got the schematic and made sure my layout matched up with the traces on there. I concluded the problem must be one of two things:
1) my op amp chip is messed up, in which case, I am sorry for wasting your time.
or
2) I am doing the power supply setup wrong. Shouldn't the voltage always be less than 6 V after being divided? The fact that I saw a voltage over 10 makes me think that somehow I am failing to divide the voltage.
Sorry for the long post! I was trying to make it detailed to minimize the need for follow-up questions.
Thanks for your help!
I am a relative beginner trying to make a simple triangle wave (audible frequency) oscillator using TL082 op amps. My efforts on this front have been driving me a bit nuts.
This is the schematic I decided to use: http://chemelec.com/Projects/Osc-2/Oscillator-a.png
I know that op amps like this one use both + and - voltage and I have never dealt with a bipolar power supply before. Based on what I have read recently, however, it looks like just by following this schematic the two 10k resistors on the left will be dividing the voltage to set up a virtual ground and provide the + and - voltage the op amp needs.
So I built the circuit on my breadboard and it did not oscillate at all. I used a 12v regulated ac/dc adapter and just connected + tip to where it says "12 Volts DC" on the schematic and the ground symbols to the -, as I normally would. It looks to me that this schematic was designed so that a person with zero understanding of the concept of bipolar power supplies could just build it like any other circuit and it would still work, so that is what I did... am I missing something though? Is the negative supposed to be hooked up to something/somewhere else?
The only thing I did differently from the schematic was that I didn't use a tantalum capacitor because I didn't have one. I used a 1 uf electrolytic at first, then tried it with a few ceramics in parallel to add up to 1 uf, with no change. However, I figured this couldn't be the problem because it seems like it is just a decoupling capacitor, and either way it was still the right value.
I checked the voltage at the point that is supposed to be the triangle wave output and it was steady at 10.52 V. I checked the squarewave output and it was exactly the same. I didn't do the calculations but I'm guessing that is nothing more than the result of the resistors that it has passed through up to those points. I checked all my connections on the breadboard and had a friend (with about as much experience as me, but who also has a basic ability to read schematics) check them too. I even looked at the PCB image on the site where I got the schematic and made sure my layout matched up with the traces on there. I concluded the problem must be one of two things:
1) my op amp chip is messed up, in which case, I am sorry for wasting your time.
or
2) I am doing the power supply setup wrong. Shouldn't the voltage always be less than 6 V after being divided? The fact that I saw a voltage over 10 makes me think that somehow I am failing to divide the voltage.
Sorry for the long post! I was trying to make it detailed to minimize the need for follow-up questions.
Thanks for your help!