Blinky. Choice of capacitor?

When you originally captured the schematic, the image of the circuit diagram you showed us had C1 as a polarized capacitor but you added a non polarized symbol. Furthermore when you applied the footprint you chose a non polarized cap footprint.

I’ve always seen 555 circuits with a polarized cap. Any thoughts on this ?

You can use either a polarized or non polarized capacitor in this application. The 555 will alternately charge and discharge the capacitor and rely on the voltage of the capacitor going from 1/3 the supply voltage up to 2/3 the supply voltage to trigger the flip flop inside the IC that drives the output to go high or low. The voltage across the capacitor never changes polarity like an AC signal so there is no need for a non polarized capacitor but there’s nothing stopping you from using one here. Other things like package size or capacitance value would drive the decision more than the type of capacitor in this case.


Yep, agree with this assessment. Polarization usually has more to do with the construction of the cap rather than the needs of the circuit.

These days I target most things at ceramic, which is unpolarized and suggest you do the same. Only on really large capacitances do I consider polarized caps.

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