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How to implement this circuit

Hanna123

New Member
Hello,
I have a group project and we are sending a signal through induction. We have created a LTspice simulation and now we are supposed to implement the circuit in real life. Can someone please help me? My biggest concerns is how to make the square wave, generated by the 555-timer, centered around 0 volt? How to protect the 555-timer from too high currents? We only have access to a +-25 V DC cube. Skärmavbild 2019-02-04 kl. 14.42.33.png
 

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ronsimpson

Well-Known Member
Most Helpful Member
When I got the circuit the current in L1 is much greater than the current in L2. The NE555 is hot! I added R7 to reduce the current to 25mA.
I changed U2 to a differential amp to solve the 2.5V offset. R3=R9, R8=(R10||R2)
R10 and R2 looks like 10k to (4.5V/2) or 10k to 2.25V.
1549295410950.png
The circuit has problems but here is one idea.
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Normally I would "AC couple" the signal and set back to ground. But L1, C3 caused problems and I could not see a fast way around that so I did not AC couple. I think AC coupling is the answer.
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There is a problem that when RST is on the output is held low which causes large currents in L2. (both circuits)
 

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Hanna123

New Member
Thank you so much for the help. You really saved us! I just have one more question, how do we know the number (datasheet) for the opamp you are using. So we can buy it and implement it in the real life circuit.

Best regards, Hanna
 

AnalogKid

Well-Known Member
Most Helpful Member
If you really want to run the opamp on +/-25 V, you will need a specialized high voltage device. Standard opamps have a max operating voltage of +/-18 V to +/-22 V.

Where are you located? Do you have access to a full-line distributor?

ak
 

ronsimpson

Well-Known Member
Most Helpful Member
LTC6090 is probably a good place to start. You are using LtSpice so there should be a modle.
High voltage silicon is hard to find now.

In your circuit the LC frequency does not match the NE555 frequency!
Here I added the LTC6090.
I canged the center filter to remove DC and high frequencies. C6R9 removes the 2.5V offset. and removes the DC when the NE555 is held in reset.
Changed L1 C3 value to right frequency.
Added C5 to remove DC. Changed C4 value.
-----edited----- Should connect /TF and /OD on the amplifier ----edited-----
1549554059085.png
 

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