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I designed a circuit that is similar to the circuit on the picture below. The main difference in my design is that I am using a 3V battery and more LEDs.

enter image description here

I am using UNPOLARISED capacitors because I am aware of the oscillating voltages on the two capacitors. I also manufactured the PCB and it works like a charm.

Because unpolarised capacitors are large, expensive and I found only THT (I want SMD), I am interested in using ELECTROLYTIC POLARISED capacitors - and assuming that it is not dangerous since it is a low voltage circuit (3V battery is used, so the reverse voltage on the cap should be max around 1V).

I have already tried the circuit with polarised electrolytic capacitors (specifications 330uF, 16V) and it works just fine, and the capacitors are cold, so it seems safe. But I would like a comment from more experience guys before I make 20 PCBs and than realize that after 5 days the capacitors cause a fire or something...

Thanks!

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  • \$\begingroup\$ They won't cause a fire, not with 100k in series with the tiny negative voltage that's the difference between Vbe and Vce(sat), for the brief moment that they're actually reversed. \$\endgroup\$ – Neil_UK Dec 10 '17 at 14:14
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    \$\begingroup\$ Polarised capacitors can have an reverse voltage on them; this value is limited by its properties. \$\endgroup\$ – Daniel Tork Dec 10 '17 at 17:05
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The is okay to do, however a higher voltage rating on the capacitors is better, best not to substitute 6.3V caps.

The reverse voltage in your circuit is limited to a diode drop minus Vce(sat) which is acceptable for a conventional 16V aluminum electrolytic capacitor.

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