Electrical – 60hz Astable 555 timer circuit not oscillating

You should have a bypass capacitor across the supply terminals, close to the TLC555. Something like 10uF electrolytic in parallel with 1uF ceramic.

Bypassing the CONT pin as you have done may have more effect on the frequency if the supply rails are not adequately bypassed.

You might also want to put a resistor in series with the MOSFET gate to limit the current, and to use a MOSFET that has low gate charge (don't use a huge MOSFET if you don't need to).

Changes in the supply voltage during the cycle when the LEDs are on will affect the frequency so it would be better if the TLC555 was supplied with a separate regulated supply, or at least an RC.

Many of these effects can be reduced if you hang a flip-flop or two on the output and run the oscillator at 2x or 4x. You'll also get much closer to 50% duty cycle.

Unlike the bipolar 555, the TLC555 will give very close to 50% duty cycle with the configuration you are using, but the supply voltage has to remain very steady and the output reasonably lightly loaded.

As practically everyone has commented, electrolytic capacitors are not usually chosen for precise timing applications. CDE capacitors have typical capacitance tolerances of ±20%, –10% +50%, and –10% +75%. So your circuit is most likely working perfectly, but the value of the capacitor is not known.

However, since you have the circuit built and running, you can use it to estimate the resistor values required to make the circuit operate at your desired frequency. If you are at 1.5 Hz, you are at 1.5/1.733 or 86.6% of your target frequency. You can achieve 1.733 Hz by multiplying the values of the two timing resistors by 0.866, which would yield (in this case) 4.76K and 33.3K. You can do the math and put in parallel resistors to achieve this result. Even if you were to spend the money and get precision resistors and capacitors, the 555 timers will vary a couple of percent from chip to chip, so that in practice it is common to build a circuit that gives a too-low frequency (just as you have done) and leave pads to add parallel resistors to the timing resistors which are selected to compensate for component errors.

Good luck!