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As crutschow mentioned, the circuit is based on a standard 555 astable configuration. I tested this circuit separately and the 555 outputs an offset (positive only) square wave as desired.
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No, it's wrong. The standard astable circuit is shown below;

Note the difference to yours. In your circuit with the two equal 1k resistors, when discharge pin7 goes low the voltage on the cap C2 can only discharge to half of Vcc (due to the 1k:1k voltage divider).

It will not oscillate unless the voltage on C2 can charge >2/3 Vcc and discharge to less than 1/3 of Vcc.

Your faulty circuit might oscillate if the resistors were changed from 1k:1k to >2k:1k, ie that ratio may then allow discharge pin7 to lower the cap voltage to less than 1/3 of Vcc.

As your circuit is drawn, with those parts values it will not oscillate. Also it cannot oscillate AND run at 50:50 duty, as to reach <1/3 Vcc means the ratio of resistors cannot be 1:1, they need to be >2:1.

If you want a 555 circuit that works and makes 50:50 duty you can charge and discharge C2 through ONE resistor only, to output pin 3.

 

Shocking!

So from what I read, a Schottky diode will do the trick (or am I better off with a normal diode?).
I happen to have a 40V rated one. Added to the diagram attached. The model I have is actually the 1N5819. I do have normal diodes available too in case it fails.

I guess this would also help reducing the voltage spikes I used to see on the oscilloscope, right?

It will reduce the voltage but that's because the diode will basically short circuit the flyback voltage that you are trying to generate.

 

Well, I just came back from the lab after a highly disappointing experience. For some reason the 555 circuit wasn't outputting anything at all. I think both 555 IC's I had must have been damaged somehow. No progress made.

No, it's wrong. The standard astable circuit is shown below;

Note the difference to yours. In your circuit with the two equal 1k resistors, when discharge pin7 goes low the voltage on the cap C2 can only discharge to half of Vcc (due to the 1k:1k voltage divider).

It will not oscillate unless the voltage on C2 can charge >2/3 Vcc and discharge to less than 1/3 of Vcc.

Your faulty circuit might oscillate if the resistors were changed from 1k:1k to >2k:1k, ie that ratio may then allow discharge pin7 to lower the cap voltage to less than 1/3 of Vcc.

As your circuit is drawn, with those parts values it will not oscillate. Also it cannot oscillate AND run at 50:50 duty, as to reach <1/3 Vcc means the ratio of resistors cannot be 1:1, they need to be >2:1.

If you want a 555 circuit that works and makes 50:50 duty you can charge and discharge C2 through ONE resistor only, to output pin 3.

Weird. I actually built that circuit before with success. The values I got I actually calculated from the same website you posted that picture.

Regardless, today when I tried implementing this circuit it didn't work, even when I increased the value of R1.

Still thanks for pointing it out, I will investigate it further.

It will reduce the voltage but that's because the diode will basically short circuit the flyback voltage that you are trying to generate.

I'm confused, so is the extra diode a good or bad thing?

Thanks

 

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I'm confused, so is the extra diode a good or bad thing?

It's bad if you want an output from the flyback. The diode will basically dissipate the inductive energy when the transistor turns off instead of it going to the secondary. A diode is fine if you are powering an inductive load such as a solenoid or relay and want to suppress the inductive spike energy but in a flyback you want the energy to go to the output winding.

 

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Weird. I actually built that circuit before with success. The values I got I actually calculated from the same website you posted that picture.
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Don't sweat it. It's possible you miswired a resistor which is very easy to do and that originally let the circuit oscillate.

If you want a really simple reliable 50:50 oscillator with the 555, just remove both your 1k resistors from the circuit, then put a single resistor between the cap C2 (555 pins 2,6) and the output of the 555 IC (pin 3).

The 555 output is inverted compared to it's cap input, so that makes a very simple 50:50 duty RC inverter oscillator.