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I am using the k7805 DC/DC converters from morson for my project and I’m struggling to find correct ceramic capacitors.

Also on the data sheet in fig 1 it shows polarised capacitors but I didn’t think ceramic have polarity.

I can’t find 22μF/10V ceramic anywhere, only in electrolytic.

Found plenty of 0.22μF

datasheet

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Ceramic capacitors aren’t polarised - I’d suggest the polarity on the diagram is included for completeness.

You might be looking for leaded 22uF ceramic caps in which case I can understand your difficulty in finding them as they tend to be only available in surface mount.

Depending on your application, electrolytic caps might be sufficient. Ceramic caps are suggested as they have lower ESR (equivalent series resistance) and in most cases lower is better. Ceramics also don’t ‘dry out’ over time like electrolytics do.

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  • \$\begingroup\$ It’s powering as esp32 board and some relays \$\endgroup\$
    – robbrown92
    Commented Feb 8, 2022 at 23:28
  • \$\begingroup\$ I gather there’s a linear regulator for the esp32 3.3V supply. If so, electros should be adequate. For the larger relays (10Aor so) I would lean towards 12V or 24V coils. Less current for the coil and a little more voltage tolerance. With a 5V coil switched by a uln2003 chip you loose a volt or so due to the uln2003. That means you are in the edge of the coil voltage spec. With a 12V coil, you would still be in spec. A transistor will loose a few 10’s of a volt and a mosfet would depend on the actual device specs. \$\endgroup\$
    – Kartman
    Commented Feb 8, 2022 at 23:39
  • \$\begingroup\$ from what I have learned, use a electrolytic cap plus add a smaller ceramic capacitor in parallel - the ceramic capacitor will improve the ESR and the combined caps will have a better frequency response - even e.g. 3 ceramics in parallel are better than just one. ksim3.kemet.com/capacitor-simulation provides a tool to simulate that (don't know if it can combine electrolytic and ceramic caps) \$\endgroup\$
    – schnedan
    Commented Feb 9, 2022 at 0:12
  • \$\begingroup\$ @Kartman There is a 3.3v ldo powering the ESP. The issue I have with 12v relays is maintaining a constant 12v as the relays only have a allowable voltage max of 120% which gives me 14.4v. There isn't enough of a voltage difference to use a voltage regulator. would the ULN2003 bring the 14.8v down to within tolerance for the relays? I've never used one before but from reading the datasheet it can be used on 3.3v logic and the output of the chip is the gnd to the 12v relay? \$\endgroup\$
    – robbrown92
    Commented Feb 9, 2022 at 9:24

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